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    Angiotensin Converting Enzyme Inhibitor/ACEIs and Calcium Channel Blocker Combinations

    BOXED WARNING

    Pregnancy

    Trandolapril; verapamil is classified as FDA pregnancy risk category D. Once pregnancy is detected, every effort should be made to discontinue trandolapril; verapamil therapy. Women of child-bearing age should be made aware of the potential risk and trandolapril; verapamil should only be given after careful counseling and consideration of individual risks and benefits. When used during the second and third trimesters, drugs that affect the renin-angiotensin system (e.g., ACE inhibitors, angiotensin II receptor antagonists) reduce fetal renal function and increase fetal and neonatal morbidity and death. Resulting oligohydramnios can be associated with fetal lung hypoplasia and skeletal deformations. Other potential neonatal adverse effects include skull hypoplasia, anuria, and hypotension. Retrospective data indicate that first trimester use of ACE inhibitors has been associated with a potential risk of birth defects. However, a large observational study (n = 465,754) found that the risk of birth defects was similar in infants exposed to ACE inhibitors during the first trimester, in infants exposed to other antihypertensives during the first trimester, and in those whose mothers were hypertensive but were not treated. Infants born to mothers with hypertension, either treated or untreated, had a higher risk of birth defects than those born to mothers without hypertension. The authors concluded that the presence of hypertension likely contributed to the development of birth defects rather than the use of medications. In rare cases when another antihypertensive agent cannot be used to treat a pregnant patient, serial ultrasound examinations should be performed to assess the intraamniotic environment. If oligohydramnios is observed, discontinue trandolapril; verapamil unless it is considered life-saving for the mother. It should be noted that oligohydramnios may not appear until after the fetus has sustained irreversible injury. Closely observe newborns with histories of in utero exposure to trandolapril; verapamil for hypotension, oliguria, and hyperkalemia. If oliguria or hypotension occurs, blood pressure and renal perfusion support may be required, as well as exchange transfusion or dialysis to reverse hypotension and/or support decreased renal function.

    DEA CLASS

    Rx

    DESCRIPTION

    ACE inhibitor and CCB; used qd for HTN; oral combination product contains immediate-release trandolapril and extended-release verapamil; has greater antihypertensive effects than either agent alone.

    COMMON BRAND NAMES

    Tarka

    HOW SUPPLIED

    Tarka/Trandolapril, Verapamil/Trandolapril, Verapamil Hydrochloride Oral Tab ER: 1-240mg, 2-180mg, 2-240mg, 4-240mg

    DOSAGE & INDICATIONS

    For the treatment of hypertension in patients who do not respond to monotherapy.
    NOTE: Individualize the dosage by titration of the separate components. If the optimal dose corresponds to the ratio contained in the combination formulation, this product can be used for convenient dosing.
    NOTE: The possibility of exacerbation of hypotensive effects with trandolapril; verapamil in patients taking diuretics may be minimized by either discontinuing the diuretic or cautiously increasing the salt intake prior to initiating this combination. If it is not possible to discontinue the diuretic, the starting dose should be reduced.
    Oral dosage
    Adults

    A patient whose blood pressure is not adequately controlled with either trandolapril or verapamil monotherapy may be given this combination drug product. Oral trandolapril and verapamil should be individually titrated to clinical goals before to switching to the appropriate dose ratio of Tarka (available in 2—180, 1—240, 2—240, and 4—240 mg of trandolapril and verapamil, respectively). Patients receiving diuretics should be initiated at lower doses. Maximum antihypertensive effects occur within about 1 week. Maximum dosage for combination therapy is 8 mg/day PO for trandolapril and 240 mg/day PO for verapamil. The recommended usual dosage range for trandolapril monotherapy is 1 to 4 mg/day administered once daily (or two divided doses). The recommended usual dosage range for monotherapy with sustained-release verapamil is 120 to 480 mg/day administered once daily (or two divided doses). Correct volume and/or sodium depletion prior to administration. Monitor closely for symptomatic hypotension.

    Geriatric

    Use the combination only after titrating the separate drug components. The initial doses of verapamil should be reduced in elderly patients. Greater sensitivity to the antihypertensive effects of verapamil and trandolapril is possible in elderly patients. Adjust the dosage based on clinical response.

    MAXIMUM DOSAGE

    Adults

    8 mg/day PO trandolapril and 240 mg/day PO verapamil.

    Elderly

    8 mg/day PO trandolapril and 240 mg/day PO verapamil.

    Adolescents

    Safety and efficacy have not been established.

    Children

    Safety and efficacy have not been established.

    DOSING CONSIDERATIONS

    Hepatic Impairment

    Use this combination drug product only after titrating the separate drug components. In patients with hepatic cirrhosis, the initial trandolapril dose is 0.5 mg/day and may be increased slowly (see Trandolapril monograph, Dosage section). In patients with hepatic disease, the verapamil initial dosage should be reduced to about 33% of the usual dosage (see Verapamil monograph, Dosage section). Verapamil and trandolapril dosage should be adjusted based on clinical response. The combination drug product has not been evaluated in subjects with impaired hepatic function.

    Renal Impairment

    CrCl > 30 ml/min: No dosage adjustment is necessary.
    CrCl <= 30 ml/min: Use this combination drug product only after titrating the separate drug components. The initial trandolapril dose is 0.5 mg/day PO and may be increased slowly to a maximum of 2 mg/day PO (see Trandolapril monograph, Dosage section).
     
    Intermittent hemodialysis
    Use this combination drug product only after titrating the separate drug components. Verapamil and norverapamil are not removed by hemodialysis. Trandolaprilat is removed by hemodialysis; and hemodialysis patients have a reduced clearance of trandolaprilat. No specific dosage recommendations are available for dialysis patients.

    ADMINISTRATION

    Oral Administration

    Do not administer with grapefruit juice, which may significantly increase verapamil serum concentrations.

    Oral Solid Formulations

    Administer trandolapril; verapamil with food. Swallow tablets whole; do not break, crush, or chew.

    STORAGE

    Tarka:
    - Store at controlled room temperature (between 68 and 77 degrees F)

    CONTRAINDICATIONS / PRECAUTIONS

    ACE-inhibitor induced angioedema, angioedema, Angiotensin-converting enzyme inhibitors (ACE inhibitors) hypersensitivity, Black patients, hereditary angioedema


    Angiotensin-converting enzyme inhibitors (ACE inhibitors) hypersensitivity usually manifests as a result of alterations in kinin generation in sensitive individuals; there is no evidence of a specific immune-mediated reaction. However, such reactions can be potentially life-threatening, even if they are not true 'allergic' reactions. Trandolapril; verapamil is contraindicated in patients with a history of ACE-inhibitor induced angioedema, and should not be used in patients with a history of hereditary angioedema or idiopathic angioedema. If angioedema occurs, ACE inhibitor therapy should be halted and appropriate treatment instituted. The incidence of ACE-inhibitor induced angioedema is higher in Black patients than non-Black patients. In addition, ACE inhibitors are less effective in lowering blood pressure in Black patients, including the African-American population.

    Acute myocardial infarction, bradycardia, cardiogenic shock, heart failure, ventricular dysfunction

    Trandolapril; verapamil is contraindicated in cardiogenic shock due to the potential for further reductions in cardiac output and blood pressure. Trandolapril; verapamil is also contraindicated in patients with severe left ventricular dysfunction. Verapamil should be used cautiously in patients with ventricular dysfunction, severe bradycardia, congestive heart failure and/or in patients taking beta-adrenergic blocking agents (see Drug Interactions) because verapamil can precipitate or exacerbate heart failure in these patients, or cause excessive bradycardia or cardiac conduction abnormalities. In patients receiving digoxin, verapamil may further depress AV node conduction, possibly leading to varying degrees of conduction block (see Drug Interactions). Verapamil should not be used in patients with acute myocardial infarction and associated left ventricular dysfunction.

    AV block, sick sinus syndrome

    Trandolapril; verapamil is contraindicated in patients with sick sinus syndrome or advanced heart block (second- or third-degree AV block) who do not have a functioning artificial pacemaker in place. Use of verapamil in patients with these conditions may lead to shock, bradycardia, or asystole.

    Atrial fibrillation, atrial flutter, Lown-Ganong-Levine syndrome, ventricular tachycardia, Wolff-Parkinson-White syndrome

    Trandolapril; verapamil is contraindicated in patients with atrial flutter or atrial fibrillation and an accessory bypass tract (e.g.,Wolff-Parkinson-White syndrome or Lown-Ganong-Levine syndrome). In these patients, verapamil can paradoxically increase ventricular rate due to uninhibited antegrade conduction through the accessory bypass tract, resulting in potentially life-threatening conditions (ventricular fibrillation or cardiac arrest). Patients with these reentrant arrhythmias with a functioning artificial ventricular pacemaker may use still use a calcium channel blocker. Proper differentiation between supraventricular tachycardia and ventricular tachycardia (wide complex) is crucial when administering verapamil. Although verapamil may be effective in treating the former, administration to patients with ventricular tachycardia can cause ventricular fibrillation, severe hemodynamic deterioration, or death.

    Myasthenia gravis, neuromuscular disease

    Trandolapril; verapamil should be used with caution in patients with neuromuscular disease. Verapamil has been reported to decrease neuromuscular transmission in patients with Duchenne's muscular dystrophy and causes a worsening of myasthenia gravis. Verapamil also may prolong recovery from neuromuscular blockade with neuromuscular blockers such as vecuronium (see Drug Interactions).

    Constipation, fecal impaction, GI obstruction, ileus

    Verapamil is frequently causes constipation. Trandolapril; verapamil should be used cautiously in patients with GI obstruction or ileus, fecal impaction, or pre-existing constipation.

    Diabetes mellitus, hyperkalemia

    Trandolapril; verapamil should be used with caution in patients with hyperkalemia. ACE inhibitors can worsen preexisting hyperkalemia by elevating serum potassium concentrations. Hyperkalemia is associated with serious cardiac arrhythmias. Patients at risk include those with renal dysfunction, diabetes mellitus, and those patients receiving potassium-containing medicines or potassium-sparing diuretics (see Drug Interactions).

    Autoimmune disease, bone marrow suppression, collagen-vascular disease, immunosuppression, renal artery stenosis, renal disease, renal failure, renal impairment, scleroderma, systemic lupus erythematosus (SLE)

    Dosage adjustment of trandolapril is required in patients with moderate to severe renal impairment or renal failure. Treatment with ACE inhibitors has demonstrated favorable effects on the progression of renal disease in diabetic and nondiabetic patients; however, minor increases in BUN and serum creatinine may occur. These effects, more commonly reported in patients with renal artery stenosis or those receiving concomitant diuretic therapy, are usually reversible, and are not considered a reason to withhold therapy unless accompanied by hyperkalemia. If trandolapril; verapamil is initiated in patients with renal artery stenosis, renal function should be monitored during the first few weeks of therapy. About 70% of an administered dose of verapamil is excreted as metabolites in the urine. Until further data are available, verapamil should be administered cautiously to patients with impaired renal function. These patients should be carefully monitored for abnormal prolongation of the PR interval or other signs of overdosage. Neutropenia and/or agranulocytosis have been reported during therapy with ACE inhibitors. This effect rarely occurs in uncomplicated patients but more frequently in patients with renal impairment especially if they also have a collagen-vascular disease (e.g., systemic lupus erythematosus (SLE) or scleroderma) or are receiving concomitant immunosuppression. Data from clinical trials of trandolapril are insufficient to show that the drug does not cause agranulocytosis. Therefore, complete blood counts should be established prior to and during trandolapril; verapamil therapy whenever the drug is administered to patients with pre-existing renal disease or autoimmune disease. Trandolapril; verapamil should be used with caution in patients with pre-existing bone marrow suppression.

    Aortic stenosis, cardiomyopathy, cerebrovascular disease, coronary artery disease, dialysis, hyponatremia, hypotension, hypovolemia

    Trandolapril and verapamil decrease peripheral resistance and can worsen hypotension. Trandolapril; verapamil is contraindicated in patients with systolic blood pressures of less than 90 mm Hg (i.e., severe hypotension). Hypotension can also occur if trandolapril is administered to patients with hypovolemia or hyponatremia, or to patients receiving dialysis (see Dosage... Patients with intermittent hemodialysis) or high dose diuretics. Before initiating therapy with trandolapril, diuretics should be stopped if possible, and volume and sodium balance corrected. Trandolapril should be used cautiously in patients with congestive heart failure (initial doses should be lower than in the treatment of hypertension) because of a greater risk of developing hypotension. Hypotension may aggravate ischemia in patients with coronary artery disease or cerebrovascular disease, which may precipitate a myocardial infarction or cerebrovascular accident. Blood pressure should be monitored carefully in all patients receiving trandolapril; verapamil. Trandolapril; verapamil should be avoided in patients with aortic stenosis because it can worsen the abnormal pressure gradient associated with this condition. Verapamil should be used extremely cautiously in patients with hypertrophic cardiomyopathy because severe and sometimes fatal adverse reactions can occur such as pulmonary edema, hypotension, sinus arrest, and second-degree AV block. Trandolapril should also be used with caution with hypertrophic cardiomyopathy. As with all vasodilators, trandolapril; verapamil should be given with caution to patients with obstruction in the outflow tract of the left ventricle.

    Hymenoptera venom (insect sting) allergy desensitization, low-density lipoprotein apheresis

    Treatment with ACE inhibitors (e.g., trandolapril, verapamil) may increase the risk of anaphylactoid reactions in patients undergoing hymenoptera venom (insect sting) allergy desensitization. Two patients undergoing desensitizing treatment with hymenoptera venom while receiving ACE inhibitors sustained life-threatening anaphylactoid reactions. In the same patients, these reactions were avoided when ACE inhibitors were temporarily withheld, but they reappeared upon inadvertent rechallenge. However, a retrospective analysis of 79 patients who underwent hymenoptera venom (insect sting) allergy desensitization did not show an association between ACE inhibitor therapy and increased frequency of systemic reactions to venom immunotherapy. Of 17 patients taking an ACE inhibitor while undergoing desensitization, none experienced a systemic reaction to venom immunotherapy; whereas, 13 of 62 patients not taking an ACE inhibitor experienced a systemic reaction during venom immunotherapy. Anaphylactoid reactions have been reported in patients taking ACE inhibitors (enalapril) who were receiving dialysis with high-flux membranes; the mechanism is unknown. When anaphylactoid symptoms such as nausea, abdominal cramps, burning, angioedema, shortness of breath or low blood pressure are recognized, the dialysis should be stopped and the patient should receive aggressive treatment for the hypersensitivity reaction. Anaphylactoid reactions have also occurred in patients undergoing low-density lipoprotein apheresis with dextran sulfate absorption (a procedure dependent upon devices not approved in the United States). Although a causal relationship to ACE inhibitor therapy has not been firmly established, treatment with trandolapril may increase the risk for anaphylactoid reactions during membrane exposure. ACE inhibitors may also precipitate low blood pressure in dialysis patients who are volume-depleted. 

    Geriatric

    In placebo-controlled studies, where 23% of patients receiving trandolapril; verapamil were 65 years and older, and 2.4% were 75 years and older, no overall differences in effectiveness or safety were observed between these patients and younger adults. Geriatric patients can experience a delayed clearance of verapamil and can be at greater risk for accumulation and toxicity. Dosage adjustments of trandolapril; verapamil may be necessary in older adult patients. Greater sensitivity to the hypotensive effects of the drug combination is also possible in some older adults. According to the Beers Criteria, non-dihydropyridine calcium channel blockers including verapamil are considered potentially inappropriate medications (PIMs) for use in geriatric patients with heart failure due to the potential for fluid retention and exacerbation of the condition; however, avoidance is only recommended in heart failure patients with a reduced ejection fraction.

    Hepatic disease

    Patients with hepatic disease, such as cirrhosis or hepatic failure, can experience a delayed clearance of verapamil and can be at greater risk for accumulation and toxicity. The half-life of verapamil may be increased up to 14—16 hours in patients with hepatic impairment and plasma clearance may be reduced by 30%. Trandolapril and trandolaprilat serum concentrations are increased significantly in patients with liver disease. Patients with hepatic impairment should receive dosage individualization of verapamil and trandolapril before initiating the fixed combination product.

    Surgery

    Trandolapril; verapamil should be used with caution in patients undergoing surgery. Trandolapril will block angiotensin II formation secondary to compensatory renin release in patients undergoing major surgery or during anesthesia with agents that produce hypotension. If hypotension occurs and is considered to be due to this mechanism, it can be corrected by volume expansion. Verapamil also may prolong recovery from neuromuscular blockers (see Drug Interactions).

    Pregnancy

    Trandolapril; verapamil is classified as FDA pregnancy risk category D. Once pregnancy is detected, every effort should be made to discontinue trandolapril; verapamil therapy. Women of child-bearing age should be made aware of the potential risk and trandolapril; verapamil should only be given after careful counseling and consideration of individual risks and benefits. When used during the second and third trimesters, drugs that affect the renin-angiotensin system (e.g., ACE inhibitors, angiotensin II receptor antagonists) reduce fetal renal function and increase fetal and neonatal morbidity and death. Resulting oligohydramnios can be associated with fetal lung hypoplasia and skeletal deformations. Other potential neonatal adverse effects include skull hypoplasia, anuria, and hypotension. Retrospective data indicate that first trimester use of ACE inhibitors has been associated with a potential risk of birth defects. However, a large observational study (n = 465,754) found that the risk of birth defects was similar in infants exposed to ACE inhibitors during the first trimester, in infants exposed to other antihypertensives during the first trimester, and in those whose mothers were hypertensive but were not treated. Infants born to mothers with hypertension, either treated or untreated, had a higher risk of birth defects than those born to mothers without hypertension. The authors concluded that the presence of hypertension likely contributed to the development of birth defects rather than the use of medications. In rare cases when another antihypertensive agent cannot be used to treat a pregnant patient, serial ultrasound examinations should be performed to assess the intraamniotic environment. If oligohydramnios is observed, discontinue trandolapril; verapamil unless it is considered life-saving for the mother. It should be noted that oligohydramnios may not appear until after the fetus has sustained irreversible injury. Closely observe newborns with histories of in utero exposure to trandolapril; verapamil for hypotension, oliguria, and hyperkalemia. If oliguria or hypotension occurs, blood pressure and renal perfusion support may be required, as well as exchange transfusion or dialysis to reverse hypotension and/or support decreased renal function.

    Breast-feeding

    According to the manufacturer, trandolapril; verapamil should not be administered to nursing mothers. Data for the combination product are not available. Data for trandolapril in human breast-feeding women are not available. Verapamil distributes into breast milk, and the manufacturers of verapamil products generally recommend discontinuation of breast-feeding during verapamil administration. However, given limited data that the nursing infant may not ingest a significant dosage via the milk (reported infant exposure ranged from less than 0.01% to 0.1% of the maternally ingested verapamil dose ) and due to the lack of reported adverse effects, the drug is considered usually compatible with breast-feeding by the American Academy of Pediatrics (AAP). Diltiazem, another calcium-channel blocker, is also classified as usually compatible with breast-feeding by the AAP. Trandolapril has not been evaluated by the AAP; however, captopril and enalapril are classified by the American Academy of Pediatrics (AAP) as usually compatible with breast-feeding. Benazepril and quinapril are excreted in human breast milk in very small quantities ; therefore, a clinically significant risk to a breast-feeding infant is not expected. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally ingested drug, healthcare providers are encouraged to report the adverse effect to the FDA.

    Children

    The safety and effectiveness of trandolapril; verapamil combinations have not been established in children.

    ADVERSE REACTIONS

    Severe

    ileus / Delayed / 1.0-10.0
    AV block / Early / 0.3-3.9
    bradycardia / Rapid / 1.8-1.8
    renal tubular necrosis / Delayed / 0-1.0
    glomerulonephritis / Delayed / 0-1.0
    hyperkalemia / Delayed / 0.4-0.8
    azotemia / Delayed / 0.3-0.3
    angioedema / Rapid / 0.1-0.1
    myocardial infarction / Delayed / 0.3
    laryngeal edema / Rapid / Incidence not known
    anaphylactoid reactions / Rapid / Incidence not known
    hepatic failure / Delayed / Incidence not known
    hepatic necrosis / Delayed / Incidence not known
    atrial fibrillation / Early / Incidence not known
    ventricular fibrillation / Early / Incidence not known
    pulmonary edema / Early / Incidence not known
    heart failure / Delayed / Incidence not known
    pancytopenia / Delayed / Incidence not known
    agranulocytosis / Delayed / Incidence not known
    hemolytic anemia / Delayed / Incidence not known
    aplastic anemia / Delayed / Incidence not known
    toxic epidermal necrolysis / Delayed / Incidence not known
    exfoliative dermatitis / Delayed / Incidence not known
    Stevens-Johnson syndrome / Delayed / Incidence not known
    pemphigus / Delayed / Incidence not known
    erythema multiforme / Delayed / Incidence not known
    teratogenesis / Delayed / Incidence not known
    stroke / Early / Incidence not known
    pancreatitis / Delayed / Incidence not known

    Moderate

    constipation / Delayed / 3.3-3.3
    elevated hepatic enzymes / Delayed / 2.8-2.8
    chest pain (unspecified) / Early / 2.2-2.2
    edema / Delayed / 1.3-1.3
    dyspnea / Early / 1.3-1.3
    pneumonitis / Delayed / 0-1.0
    hypotension / Rapid / 0.6-0.6
    blurred vision / Early / 0.3
    hematuria / Delayed / 0.3
    confusion / Early / 0.3
    gout / Delayed / 0.3
    proteinuria / Delayed / 0.3
    impotence (erectile dysfunction) / Delayed / 0.3
    premature ventricular contractions (PVCs) / Early / 0.3
    angina / Early / 0.3
    bundle-branch block / Early / 0.3
    sinus tachycardia / Rapid / 0.3
    palpitations / Early / 0.3
    leukopenia / Delayed / 0.3
    neutropenia / Delayed / 0.3
    hepatitis / Delayed / Incidence not known
    jaundice / Delayed / Incidence not known
    cholestasis / Delayed / Incidence not known
    peripheral vasodilation / Rapid / Incidence not known
    peripheral edema / Delayed / Incidence not known
    gingival hyperplasia / Delayed / Incidence not known
    thrombocytopenia / Delayed / Incidence not known
    galactorrhea / Delayed / Incidence not known
    psychosis / Early / Incidence not known
    hyperprolactinemia / Delayed / Incidence not known

    Mild

    headache / Early / 8.9-8.9
    cough / Delayed / 4.6-4.6
    dizziness / Early / 3.1-3.1
    fatigue / Early / 2.8-2.8
    arthralgia / Delayed / 1.7-1.7
    nausea / Early / 1.5-1.5
    diarrhea / Early / 1.5-1.5
    syncope / Early / 0.1-0.1
    polyuria / Early / 0.3
    pruritus / Rapid / 0.3
    vertigo / Early / 0.3
    weakness / Early / 0.3
    myalgia / Early / 0.3
    anxiety / Delayed / 0.3
    drowsiness / Early / 0.3
    rash (unspecified) / Early / 0.3
    hypoesthesia / Delayed / 0.3
    nocturia / Early / 0.3
    insomnia / Early / 0.3
    malaise / Early / 0.3
    epistaxis / Delayed / 0.3
    paresthesias / Delayed / 0.3
    tinnitus / Delayed / 0.3
    flushing / Rapid / 0.3
    dyspepsia / Early / 0.3
    xerostomia / Early / 0.3
    gynecomastia / Delayed / Incidence not known
    libido decrease / Delayed / Incidence not known
    alopecia / Delayed / Incidence not known
    fever / Early / Incidence not known
    photosensitivity / Delayed / Incidence not known
    urticaria / Rapid / Incidence not known
    hyperkeratosis / Delayed / Incidence not known
    increased urinary frequency / Early / Incidence not known
    ecchymosis / Delayed / Incidence not known

    DRUG INTERACTIONS

    Acalabrutinib: (Major) Decrease the acalabrutinib dose to 100 mg PO once daily if coadministered with verapamil. Coadministration may result in increased acalabrutinib exposure and toxicity (e.g., infection, bleeding, and atrial arrhythmias). Acalabrutinib is a CYP3A4 substrate; verapamil is a moderate CYP3A4 inhibitor. In physiologically based pharmacokinetic (PBPK) simulations, the Cmax and AUC values of acalabrutinib were increased by 2- to almost 3-fold when acalabrutinib was coadministered with moderate CYP3A inhibitors.
    Acebutolol: (Moderate) Oral calcium-channel blockers and beta-blockers like acebutolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Acetaminophen; Aspirin, ASA; Caffeine: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Acetaminophen; Butalbital: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added.
    Acetaminophen; Butalbital; Caffeine: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Acetaminophen; Butalbital; Caffeine; Codeine: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Acetaminophen; Caffeine; Dihydrocodeine: (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Acetaminophen; Caffeine; Magnesium Salicylate; Phenyltoloxamine: (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Acetaminophen; Caffeine; Phenyltoloxamine; Salicylamide: (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Acetaminophen; Chlorpheniramine; Phenylephrine; Phenyltoloxamine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Acetaminophen; Dextromethorphan; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Acetaminophen; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Acetaminophen; Dichloralphenazone; Isometheptene: (Major) Isometheptene has sympathomimetic properties. Patients taking antihypertensive agents may need to have their therapy modified. Careful blood pressure monitoring is recommended. (Major) Isometheptene has sympathomimetic properties. Patients taking antihypertensive agents may need to have their therapy modified. Careful blood pressure monitoring is recommended.
    Acetaminophen; Guaifenesin; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Acetaminophen; Hydrocodone: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects.
    Acetaminophen; Oxycodone: (Moderate) Concomitant use of oxycodone with verapamil may increase oxycodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of oxycodone until stable drug effects are achieved. Discontinuation of verapamil could decrease oxycodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to oxycodone. If verapamil is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Oxycodone is a substrate for CYP3A4 and verapamil is a CYP3A4 inhibitor.
    Acetaminophen; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Acrivastine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Afatinib: (Major) If the concomitant use of verapamil and afatinib is necessary, consider reducing the afatinib dose by 10 mg per day if the original dose is not tolerated; resume the previous dose of afatinib as tolerated after discontinuation of verapamil. Afatinib is a P-glycoprotein (P-gp) substrate and inhibitor in vitro, and verapamil is a P-gp inhibitor; coadministration may increase plasma concentrations of afatinib. Administration of another P-gp inhibitor, ritonavir (200 mg twice daily for 3 days), 1 hour before afatinib (single dose) increased the afatinib AUC and Cmax by 48% and 39%, respectively; there was no change in the afatinib AUC when ritonavir was administered at the same time as afatinib or 6 hours later. In healthy subjects, the relative bioavailability for AUC and Cmax of afatinib was 119% and 104%, respectively, when coadministered with ritonavir, and 111% and 105% when ritonavir was administered 6 hours after afatinib. The manufacturer of afatinib recommends permanent discontinuation of therapy for severe or intolerant adverse drug reactions at a dose of 20 mg per day, but does not address a minimum dose otherwise.
    Aldesleukin, IL-2: (Moderate) Angiotensin converting enzyme inhibitors, like other antihypertensive agents, may potentiate the hypotension seen with aldesleukin, IL 2. (Moderate) Calcium channel blockers may potentiate the hypotension seen with aldesleukin, IL 2.
    Alemtuzumab: (Moderate) Alemtuzumab may cause hypotension. Careful monitoring of blood pressure and hypotensive symptoms is recommended especially in patients with ischemic heart disease and in patients on antihypertensive agents. (Moderate) Alemtuzumab may cause hypotension. Careful monitoring of blood pressure and hypotensive symptoms is recommended especially in patients with ischemic heart disease and in patients on antihypertensive agents.
    Alfentanil: (Moderate) Alfentanil may cause bradycardia. The risk of significant hypotension and/or bradycardia during therapy with alfentanil is increased in patients receiving calcium-channel blockers. In addition to additive hypotensive effects, calcium-channel blockers that are CYP3A4 inhibitors (e.g., diltiazem, nicardipine, and verapamil) can theoretically decrease hepatic metabolism of some opiates (CYP3A4 substrates), such as alfentanil. Diltiazem increases the half-life of alfentanil by 50% via inhibition of cytochrome P450 (CYP) 3A4 metabolism and may delay tracheal extubation after anesthesia. Reduced clearance of alfentanil should be considered when recovery from alfentanil infusions for anesthesia is evaluated in patients receiving concurrent diltiazem therapy.
    Alfuzosin: (Moderate) Monitor blood pressure if coadministration of alfuzosin and verapamil is necessary. This combination has the potential to cause hypotension in some patients. Coadministration may also result in increased alfuzosin serum concentrations. Alfuzosin is primarily metabolized by the CYP3A4 hepatic enzyme. In addition to potential for additive hypotension with alfuzosin, verapamil may also inhibit the metabolism of alfuzosin.
    Aliskiren: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and aliskiren do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAAS inhibitors particularly in patients with CrCl < 60 mL/min. Closely monitor blood pressure, renal function, and electrolytes if aliskiren is combined with another RAAS inhibitor. Aliskiren-containing products are contraindicated in combination with ACE inhibitors in patients with diabetes mellitus. In the ALTITUDE trial, patients with type 2 diabetes and renal impairment, a population at high risk for cardiovascular and renal events, were given aliskiren in addition to ACE inhibitors or ARBs. The trial was stopped early because aliskiren was associated with an increased risk of non-fatal stroke, renal complications, hyperkalemia, and hypotension. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. (Moderate) Administration of 240 mg verapamil with 300 mg aliskiren resulted in an approximately 2-fold increase in AUC and Cmax of aliskiren; however, no dosage adjustment is necessary. Blood pressure should be closely monitored in patients taking both of these medications.
    Aliskiren; Amlodipine: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and aliskiren do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAAS inhibitors particularly in patients with CrCl < 60 mL/min. Closely monitor blood pressure, renal function, and electrolytes if aliskiren is combined with another RAAS inhibitor. Aliskiren-containing products are contraindicated in combination with ACE inhibitors in patients with diabetes mellitus. In the ALTITUDE trial, patients with type 2 diabetes and renal impairment, a population at high risk for cardiovascular and renal events, were given aliskiren in addition to ACE inhibitors or ARBs. The trial was stopped early because aliskiren was associated with an increased risk of non-fatal stroke, renal complications, hyperkalemia, and hypotension. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. (Moderate) Administration of 240 mg verapamil with 300 mg aliskiren resulted in an approximately 2-fold increase in AUC and Cmax of aliskiren; however, no dosage adjustment is necessary. Blood pressure should be closely monitored in patients taking both of these medications. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Aliskiren; Amlodipine; Hydrochlorothiazide, HCTZ: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and aliskiren do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAAS inhibitors particularly in patients with CrCl < 60 mL/min. Closely monitor blood pressure, renal function, and electrolytes if aliskiren is combined with another RAAS inhibitor. Aliskiren-containing products are contraindicated in combination with ACE inhibitors in patients with diabetes mellitus. In the ALTITUDE trial, patients with type 2 diabetes and renal impairment, a population at high risk for cardiovascular and renal events, were given aliskiren in addition to ACE inhibitors or ARBs. The trial was stopped early because aliskiren was associated with an increased risk of non-fatal stroke, renal complications, hyperkalemia, and hypotension. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. (Moderate) Administration of 240 mg verapamil with 300 mg aliskiren resulted in an approximately 2-fold increase in AUC and Cmax of aliskiren; however, no dosage adjustment is necessary. Blood pressure should be closely monitored in patients taking both of these medications. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Aliskiren; Hydrochlorothiazide, HCTZ: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and aliskiren do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAAS inhibitors particularly in patients with CrCl < 60 mL/min. Closely monitor blood pressure, renal function, and electrolytes if aliskiren is combined with another RAAS inhibitor. Aliskiren-containing products are contraindicated in combination with ACE inhibitors in patients with diabetes mellitus. In the ALTITUDE trial, patients with type 2 diabetes and renal impairment, a population at high risk for cardiovascular and renal events, were given aliskiren in addition to ACE inhibitors or ARBs. The trial was stopped early because aliskiren was associated with an increased risk of non-fatal stroke, renal complications, hyperkalemia, and hypotension. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. (Moderate) Administration of 240 mg verapamil with 300 mg aliskiren resulted in an approximately 2-fold increase in AUC and Cmax of aliskiren; however, no dosage adjustment is necessary. Blood pressure should be closely monitored in patients taking both of these medications.
    Aliskiren; Valsartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and aliskiren do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of RAAS inhibitors particularly in patients with CrCl < 60 mL/min. Closely monitor blood pressure, renal function, and electrolytes if aliskiren is combined with another RAAS inhibitor. Aliskiren-containing products are contraindicated in combination with ACE inhibitors in patients with diabetes mellitus. In the ALTITUDE trial, patients with type 2 diabetes and renal impairment, a population at high risk for cardiovascular and renal events, were given aliskiren in addition to ACE inhibitors or ARBs. The trial was stopped early because aliskiren was associated with an increased risk of non-fatal stroke, renal complications, hyperkalemia, and hypotension. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia. (Moderate) Administration of 240 mg verapamil with 300 mg aliskiren resulted in an approximately 2-fold increase in AUC and Cmax of aliskiren; however, no dosage adjustment is necessary. Blood pressure should be closely monitored in patients taking both of these medications.
    Alkalinizing Agents: (Major) Products containing a potassium salt, including citric acid; potassium citrate; sodium citrate, should be used with caution in patients taking drugs that may increase serum potassium concentrations, such as ACE inhibitors. Concurrent use can cause hyperkalemia, especially in elderly patients or patients with impaired renal function.
    Almotriptan: (Minor) Verapamil, a moderate CYP3A4 inhibitor, increases AUC and peak plasma concentrations of almotriptan by 20% and 24%, respectively; however, per the manufacturer, the changes are not clinically significant and no dosage adjustment of almotriptan is needed. Some patients might rarely have an increase in common side effects of almotriptan, such as dizziness, nausea or drowsiness.
    Alogliptin: (Moderate) ACE inhibitors may enhance the hypoglycemic effects antidiabetic agents, such as alogliptin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. In addition, coadministration may increase the risk for angioedema.
    Alogliptin; Metformin: (Moderate) ACE inhibitors may enhance the hypoglycemic effects antidiabetic agents, such as alogliptin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. In addition, coadministration may increase the risk for angioedema. (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Alogliptin; Pioglitazone: (Moderate) ACE inhibitors may enhance the hypoglycemic effects antidiabetic agents, such as alogliptin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. In addition, coadministration may increase the risk for angioedema.
    Alpha-glucosidase Inhibitors: (Moderate) ACE inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control.
    Alprazolam: (Moderate) Consider a reduced dose of alprazolam is concurrent use of verapamil is necessary. Coadministration of alprazolam, a CYP3A4 substrate, with verapamil, a moderate CYP3A4 inhibitor, may result in increased alprazolam exposure.
    Alprostadil: (Minor) The concomitant use of systemic alprostadil injection and antihypertensive agents, like calcium channel blockers, may cause additive hypotension. Caution is advised with this combination. Systemic drug interactions with the urethral suppository (MUSE) or alprostadil intracavernous injection are unlikely in most patients because low or undetectable amounts of the drug are found in the peripheral venous circulation following administration. In those men with significant corpora cavernosa venous leakage, hypotension might be more likely. Use caution with in-clinic dosing for erectile dysfunction (ED) and monitor for the effects on blood pressure. In addition, the presence of medications in the circulation that attenuate erectile function may influence the response to alprostadil. However, in clinical trials with alprostadil intracavernous injection, anti-hypertensive agents had no apparent effect on the safety and efficacy of alprostadil. (Minor) The concomitant use of systemic alprostadil injection and antihypertensive agents, such as angiotensin-converting enzyme inhibitors (ACE inhibitors), may cause additive hypotension. Caution is advised with this combination. Systemic drug interactions with the urethral suppository (MUSE) or alprostadil intracavernous injection are unlikely in most patients because low or undetectable amounts of the drug are found in the peripheral venous circulation following administration. In those men with significant corpora cavernosa venous leakage, hypotension might be more likely. Use caution with in-clinic dosing for erectile dysfunction (ED) and monitor for the effects on blood pressure. However, in clinical trials with alprostadil intracavernous injection, anti-hypertensive agents had no apparent effect on the safety and efficacy of alprostadil.
    Alvimopan: (Moderate) Alvimopan is a substrate of P-glycoprotein (P-gp). Although the concomitant use of mild to moderate inhibitors of P-gp did not influence the pharmacokinetics of alvimopan, the concomitant use of strong P-gp inhibitors, such as verapamil has not been studied. Coadministration of verapamil and alvimopan may result in elevated concentrations of alvimopan. If these drugs are coadministered, patients should be monitored for increased toxicity as well as increased therapeutic effect of alvimopan.
    Amifostine: (Major) Patients receiving angiotensin-converting enzyme inhibitors should be closely monitored during amifostine infusions due to additive effects. Patients receiving amifostine at doses recommended for chemotherapy should have antihypertensive therapy interrupted 24 hours preceding administration of amifostine. If the antihypertensive cannot be stopped, patients should not receive amifostine. (Major) Patients receiving calcium-channel blockers should be closely monitored during amifostine infusions due to additive effects. Patients receiving amifostine at doses recommended for chemotherapy should have antihypertensive therapy interrupted 24 hours preceding administration of amifostine. If the antihypertensive cannot be stopped for 24 hours before chemotherapy doses of amifostine, patients should not receive amifostine.
    Amiloride: (Major) Amiloride should be used very cautiously with agents that have potential to induce hyperkalemia; serum potassium levels monitored when such agents are coadministered with amiloride. Simultaneous use of a potassium-sparing diuretic (e.g., amiloride) with angiotensin-converting enzyme inhibitors (ACE inhibitors) can increase the risk of hyperkalemia, especially in the presence of renal impairment (renal disease, elderly patients). These agents should be used with caution and serum potassium levels monitored when the substances are coadministered. The Beers Criteria recommends avoiding routine use of this combination in older adults; reserve this combination for patients with demonstrated hypokalemia while taking an ACE inhibitor.
    Amiloride; Hydrochlorothiazide, HCTZ: (Major) Amiloride should be used very cautiously with agents that have potential to induce hyperkalemia; serum potassium levels monitored when such agents are coadministered with amiloride. Simultaneous use of a potassium-sparing diuretic (e.g., amiloride) with angiotensin-converting enzyme inhibitors (ACE inhibitors) can increase the risk of hyperkalemia, especially in the presence of renal impairment (renal disease, elderly patients). These agents should be used with caution and serum potassium levels monitored when the substances are coadministered. The Beers Criteria recommends avoiding routine use of this combination in older adults; reserve this combination for patients with demonstrated hypokalemia while taking an ACE inhibitor.
    Amiodarone: (Major) Based on the pharmacology of amiodarone and verapamil, additive effects on cardiac contractility and/or AV conduction are possible. Concurrent use of amiodarone and verapamil may result in bradycardia, AV block, and/or depressed cardiac output; monitor clinical response. In addition, amiodarone is both a substrate and inhibitor of CYP3A4 metabolism, and may potentially interact with verapamil via CYP3A4 metabolic pathways.
    Amitriptyline; Chlordiazepoxide: (Moderate) Verapamil is a CYP3A4 inhibitor and may reduce the metabolism of chlordiazepoxide and increase the potential for benzodiazepine toxicity.
    Amlodipine: (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Atorvastatin: (Major) Verapamil may increase the serum concentrations of atorvastatin. Verapamil is a CYP3A4 inhibitor and atorvastatin is a CYP3A4 substrate. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Benazepril: (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Hydrochlorothiazide, HCTZ; Olmesartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Hydrochlorothiazide, HCTZ; Valsartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Olmesartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Telmisartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amlodipine; Valsartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia. (Moderate) When verapamil (non-dihydropyridine calcium channel blocker) and amlodipine (dihydropyridine calcium-channel blocker) are given, hypotension and impaired cardiac performance may occur, especially in patients with left ventricular dysfunction, cardiac arrhythmias, or aortic stenosis. Also, amlodipine is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. Coadministration of diltiazem (moderate CYP3A4 inhibitor) with amlodipine in elderly hypertensive patients resulted in a 60% increase in amlodipine systemic exposure. A similar pharmacokinetic effect may occur with verapamil. While concomitant use may be beneficial for carefully selected patients, caution is warranted; blood pressure, heart rate, and therapeutic response should be closely monitored.
    Amobarbital: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added. (Moderate) Concurrent use of amobarbital with antihypertensive agents may lead to hypotension. Monitor for decreases in blood pressure during times of coadministration.
    Amoxicillin; Clarithromycin; Lansoprazole: (Major) Coadministration of clarithromycin and calcium-channel blockers should be avoided if possible, particularly in geriatric patients, due to an increased risk of hypotension and acute kidney injury. Most reports of acute kidney injury were with the combination of clarithromycin with calcium channel blockers metabolized by CYP3A4 and involved elderly patients at least 65 years of age. Clarithromycin may decrease the clearance of calcium-channel blockers (e.g., amlodipine, diltiazem, felodipine, nifedipine, and verapamil) via inhibition of CYP3A4 metabolism. A retrospective, case crossover study, found the risk of hospitalization due to hypotension or shock to be significantly increased in geriatric patients exposed to clarithromycin during concurrent calcium-channel blocker therapy (OR 3.7, 95% CI 2.3-6.1). Concurrent use of azithromycin was not associated with an increased risk of hypotension (OR 1.5, 95% CI 0.8-2.8). One case of a possible verapamil-clarithromycin interaction was reported, which was associated with hypotension. If the use of a macrolide antibiotic is necessary in a patient receiving calcium-channel blocker therapy, azithromycin is the preferred agent.
    Amoxicillin; Clarithromycin; Omeprazole: (Major) Coadministration of clarithromycin and calcium-channel blockers should be avoided if possible, particularly in geriatric patients, due to an increased risk of hypotension and acute kidney injury. Most reports of acute kidney injury were with the combination of clarithromycin with calcium channel blockers metabolized by CYP3A4 and involved elderly patients at least 65 years of age. Clarithromycin may decrease the clearance of calcium-channel blockers (e.g., amlodipine, diltiazem, felodipine, nifedipine, and verapamil) via inhibition of CYP3A4 metabolism. A retrospective, case crossover study, found the risk of hospitalization due to hypotension or shock to be significantly increased in geriatric patients exposed to clarithromycin during concurrent calcium-channel blocker therapy (OR 3.7, 95% CI 2.3-6.1). Concurrent use of azithromycin was not associated with an increased risk of hypotension (OR 1.5, 95% CI 0.8-2.8). One case of a possible verapamil-clarithromycin interaction was reported, which was associated with hypotension. If the use of a macrolide antibiotic is necessary in a patient receiving calcium-channel blocker therapy, azithromycin is the preferred agent.
    Amphetamine; Dextroamphetamine Salts: (Major) Amphetamines increase both systolic and diastolic blood pressure and may counteract the activity of some antihypertensive agents, such as angiotensin-converting enzyme inhibitors. Close monitoring of blood pressure or the selection of alternative therapeutic agents may be needed. (Major) Amphetamines increase both systolic and diastolic blood pressure and may counteract the activity of some antihypertensive agents, such as calcium-channel blockers. Close monitoring of blood pressure or the selection of alternative therapeutic agents may be needed.
    Amprenavir: (Moderate) Coadministration of ritonavir with verapamil may increase the serum concentrations of verapamil, potentially resulting in verapamil toxicity. The manufacturer for ritonavir recommends caution when coadministering this combination.
    Amyl Nitrite: (Moderate) Concomitant use of nitrates with other antihypertensive agents can cause additive hypotensive effects. Dosage adjustments may be necessary. (Moderate) Nitroglycerin can cause hypotension. This action may be additive with other agents that can cause hypotension such as calcium-channel blockers. Patients should be monitored more closely for hypotension if nitroglycerin, including nitroglycerin rectal ointment, is used concurrently with a calcium-channel blocker.
    Angiotensin II receptor antagonists: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Apixaban: (Moderate) Use apixaban and verapamil together with caution in patients with significant renal dysfunction as risk of bleeding may be increased. Verapamil is a moderate CYP3A4 and P-glycoprotein (P-gp) inhibitor. Apixaban is a substrate of CYP3A4 and P-gp. In a pharmacokinetic study, apixaban Cmax and AUC increased by 31% and 40%, respectively, when given with another moderate CYP3A4 and P-gp inhibitor. Although serum concentrations of non-vitamin K oral anticoagulants have been increased in the presence of moderate inhibitors, one cohort study found that the risk of bleeding was not increased.
    Apomorphine: (Moderate) Patients receiving apomorphine may experience orthostatic hypotension, hypotension, and/or syncope. Extreme caution should be exercised if apomorphine is used concurrently with antihypertensive agents, or vasodilators such as nitrates. (Moderate) Patients receiving apomorphine may experience orthostatic hypotension, hypotension, and/or syncope. Extreme caution should be exercised if apomorphine is used concurrently with antihypertensive agents, or vasodilators such as nitrates.
    Apraclonidine: (Minor) Alpha blockers as a class may reduce heart rate and blood pressure. While no specific drug interactions have been identified with systemic agents and apraclonidine during clinical trials, it is theoretically possible that additive blood pressure reductions could occur when apraclonidine is combined with the use of antihypertensive agents. Patients using cardiovascular drugs concomitantly with apraclonidine should have their pulse and blood pressure monitored periodically. (Minor) Apraclonidine had minimal effects on heart rate and blood pressure during clinical studies in patients with glaucoma. However, it is theoretically possible that additive blood pressure reductions could occur when apraclonidine is combined with the use of antihypertensive agents. Use caution during concurrent use, especially in patients with severe, uncontrolled cardiovascular disease, including hypertension.
    Aprepitant, Fosaprepitant: (Major) Avoid the concomitant use of verapamil with aprepitant, fosaprepitant due to substantially increased exposure of aprepitant; increased verapamil exposure may also occur. If coadministration cannot be avoided, use caution and monitor for an increase in verapamil- and aprepitant-related adverse effects for several days after administration of a multi-day aprepitant regimen. Verapamil is a moderate CYP3A4 inhibitor and aprepitant is a CYP3A4 substrate. Coadministration of daily oral aprepitant (230 mg, or 1.8 times the recommended single dose) with a moderate CYP3A4 inhibitor, diltiazem, increased the aprepitant AUC 2-fold with a concomitant 1.7-fold increase in the diltiazem AUC; clinically meaningful changes in ECG, heart rate, or blood pressure beyond those induced by diltiazem alone did not occur. Verapamil is also a CYP3A4 substrate. Aprepitant, when administered as a 3-day oral regimen (125 mg/80 mg/80 mg), is a moderate CYP3A4 inhibitor and inducer and may additionally increase plasma concentrations of verapamil. For example, a 5-day oral aprepitant regimen increased the AUC of another CYP3A4 substrate, midazolam (single dose), by 2.3-fold on day 1 and by 3.3-fold on day 5. After a 3-day oral aprepitant regimen, the AUC of midazolam (given on days 1, 4, 8, and 15) increased by 25% on day 4, and then decreased by 19% and 4% on days 8 and 15, respectively. As a single 125 mg or 40 mg oral dose, the inhibitory effect of aprepitant on CYP3A4 is weak, with the AUC of midazolam increased by 1.5-fold and 1.2-fold, respectively. After administration, fosaprepitant is rapidly converted to aprepitant and shares many of the same drug interactions. However, as a single 150 mg intravenous dose, fosaprepitant only weakly inhibits CYP3A4 for a duration of 2 days; there is no evidence of CYP3A4 induction. Fosaprepitant 150 mg IV as a single dose increased the AUC of midazolam (given on days 1 and 4) by approximately 1.8-fold on day 1; there was no effect on day 4. Less than a 2-fold increase in the midazolam AUC is not considered clinically important. Finally, aprepitant is a CYP2C9 inducer and verapamil is a CYP2C9 substrate. Administration of a CYP2C9 substrate, tolbutamide, on days 1, 4, 8, and 15 with a 3-day regimen of oral aprepitant (125 mg/80 mg/80 mg) decreased the tolbutamide AUC by 23% on day 4, 28% on day 8, and 15% on day 15. The AUC of tolbutamide was decreased by 8% on day 2, 16% on day 4, 15% on day 8, and 10% on day 15 when given prior to oral administration of aprepitant 40 mg on day 1, and on days 2, 4, 8, and 15. The effects of aprepitant on tolbutamide were not considered significant.
    Aprotinin: (Moderate) The manufacturer recommends using aprotinin cautiously in patients that are receiving drugs that can affect renal function, such as ACE inhibitors, as the risk of renal impairment may be increased.
    Aripiprazole: (Moderate) Increased aripiprazole blood levels are expected when aripiprazole is coadministered with inhibitors of CYP3A4, such as verapamil. If these agents are used in combination, the patient should be carefully monitored for aripiprazole-related adverse reactions. In addition, because aripiprazole is also metabolized by CYP2D6, patients receiving a combination of a CYP3A4 and CYP2D6 inhibitor should have their oral aripiprazole dose reduced to one-quarter (25%) of the usual dose with subsequent adjustments based upon clinical response. Adults receiving a combination of a CYP3A4 and CYP2D6 inhibitor for more than 14 days should have their Abilify Maintena dose reduced from 400 mg/month to 200 mg/month or from 300 mg/month to 160 mg/month, respectively. There are no dosing recommendations for Aristada during use of a mild to moderate CYP3A4 inhibitor. (Minor) Aripiprazole may enhance the hypotensive effects of antihypertensive agents.
    Asenapine: (Moderate) Secondary to alpha-blockade, asenapine can produce vasodilation that may result in additive effects during concurrent use of antihypertensive agents. The potential reduction in blood pressure can precipitate orthostatic hypotension and associated dizziness, tachycardia, and syncope. If concurrent use of asenapine and antihypertensive agents is necessary, patients should be counseled on measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning and rising slowly from a seated position. Close monitoring of blood pressure is recommended until the full effects of the combination therapy are known.
    Aspirin, ASA: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Aspirin, ASA; Butalbital; Caffeine: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added. (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Aspirin, ASA; Butalbital; Caffeine; Codeine: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added. (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Aspirin, ASA; Caffeine; Dihydrocodeine: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Aspirin, ASA; Carisoprodol: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Aspirin, ASA; Carisoprodol; Codeine: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Aspirin, ASA; Dipyridamole: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Aspirin, ASA; Omeprazole: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Aspirin, ASA; Oxycodone: (Moderate) Concomitant use of oxycodone with verapamil may increase oxycodone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of oxycodone until stable drug effects are achieved. Discontinuation of verapamil could decrease oxycodone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to oxycodone. If verapamil is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Oxycodone is a substrate for CYP3A4 and verapamil is a CYP3A4 inhibitor. (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Aspirin, ASA; Pravastatin: (Minor) In a few reported cases, coadministration of verapamil with aspirin, ASA has led to increased bleeding times greater than observed with aspirin alone. The exact mechanism and clinical significance of this interaction is unknown.
    Atazanavir: (Moderate) Coadministration of ritonavir with verapamil may increase the serum concentrations of verapamil, potentially resulting in verapamil toxicity. The manufacturer for ritonavir recommends caution when coadministering this combination. A similar effect could be expected with other anti-retroviral protease inhibitors, which are also inhibitors of CYP3A4.
    Atazanavir; Cobicistat: (Moderate) Coadministration of cobicistat (a CYP3A4 inhibitor) with calcium-channel blockers metabolized by CYP3A4, such as verapamil, may result in elevated calcium-channel blockers serum concentrations. If used concurrently, close clinical monitoring with appropriate dose reductions are advised. (Moderate) Coadministration of ritonavir with verapamil may increase the serum concentrations of verapamil, potentially resulting in verapamil toxicity. The manufacturer for ritonavir recommends caution when coadministering this combination. A similar effect could be expected with other anti-retroviral protease inhibitors, which are also inhibitors of CYP3A4.
    Atenolol: (Moderate) Oral calcium-channel blockers and beta-blockers like atenolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Atenolol; Chlorthalidone: (Moderate) Oral calcium-channel blockers and beta-blockers like atenolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Atorvastatin: (Major) Verapamil may increase the serum concentrations of atorvastatin. Verapamil is a CYP3A4 inhibitor and atorvastatin is a CYP3A4 substrate.
    Atorvastatin; Ezetimibe: (Major) Verapamil may increase the serum concentrations of atorvastatin. Verapamil is a CYP3A4 inhibitor and atorvastatin is a CYP3A4 substrate.
    Atropine; Hyoscyamine; Phenobarbital; Scopolamine: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added.
    Avanafil: (Moderate) Avanafil is a primary substrate of CYP3A4. Studies have shown that drugs that inhibit CYP3A4 can increase avanafil exposure. Particular caution should be used when prescribing avanafil to patients receiving concomitant moderate CYP3A4 inhibitors including verapamil. For example, erythromycin increased avanafil Cmax and AUC equal to approximately 2-fold and 3-fold, respectively, and prolonged the half-life of avanafil to approximately 8 hours. Therefore, during coadministration, the maximum recommended dose of avanafil is 50 mg, not to exceed once every 24 hours.
    Axitinib: (Moderate) Use caution if coadministration of axitinib with verapamil is necessary, due to the risk of increased axitinib-related adverse reactions. Axitinib is primarily metabolized by CYP3A4, and to a lesser extent by CYP1A2, CYP2C19, and UGT1A1.Verapamil is a moderate CYP3A4 inhibitor as well as a weak inhibitor of CYP1A2. Verapamil increased exposure to simvastatin, another CYP3A4 substrate, by 2.5-fold. Coadministration with a strong CYP3A4/5 inhibitor, ketoconazole, significantly increased the plasma exposure of axitinib in healthy volunteers. The manufacturer of axitinib recommends a dose reduction in patients receiving strong CYP3A4 inhibitors, but recommendations are not available for moderate or weak CYP3A4 inhibitors.
    Azathioprine: (Major) The use of ACE inhibitors in hypertensive patients receiving azathioprine has been reported to induce anemia and severe leukopenia. This combination should be avoided where possible. When concurrent azathioprine and ACE inhibitor therapy is necessary, the patient should be monitored cautiously for potential myelosuppression.
    Azelaic Acid; Copper; Folic Acid; Nicotinamide; Pyridoxine; Zinc: (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents, especially calcium-channel blockers. This effect is of particular concern in the setting of acute myocardial infarction, unstable angina, or other acute hemodynamic compromise. (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents. (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents. (Moderate) Cutaneous vasodilation induced by niacin may become problematic if high-dose niacin is used concomitantly with other antihypertensive agents. This effect is of particular concern in the setting of acute myocardial infarction, unstable angina, or other acute hemodynamic compromise.
    Azilsartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Azilsartan; Chlorthalidone: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Azithromycin: (Moderate) Both verapamil and azithromycin are P-glycoprotein (PGP) inhibitors and substrates, so coadministration may lead to increased concentrations of either agent. Monitor patients for increased side effects if these drugs are given together.
    Baclofen: (Moderate) Baclofen has been associated with hypotension. Concurrent use with baclofen and antihypertensive agents may result in additive hypotension. Dosage adjustments of the antihypertensive medication may be required (Moderate) Baclofen has been associated with hypotension. Concurrent use with baclofen and antihypertensive agents may result in additive hypotension. Dosage adjustments of the antihypertensive medication may be required.
    Barbiturates: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added.
    Belladonna Alkaloids; Ergotamine; Phenobarbital: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added. (Major) Because of the potential to cause coronary vasospasm , ergotamine theoretically could antagonize the therapeutic effects of calcium-channel blockers. Clinicians should also note that calcium-channel blockers with CYP3A4 inhibitory properties, such as diltiazem, nicardipine, and verapamil, may also reduce the hepatic metabolism of ergotamine and increase the risk of ergot toxicity.
    Bendroflumethiazide; Nadolol: (Moderate) Oral calcium-channel blockers and beta-blockers like nadolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Benzonatate: (Moderate) Local anesthetics may cause additive hypotension in combination with antihypertensive agents.
    Benzphetamine: (Major) Benzphetamine can increase both systolic and diastolic blood pressure and may counteract the activity of angiotensin-converting enzyme inhibitors. This represents a pharmacodynamic, and not a pharmacokinetic, interaction. Close monitoring of blood pressure, especially in patients who are taking antihypertensive agents, may be needed. (Major) Benzphetamine can increase both systolic and diastolic blood pressure and may counteract the activity of calcium-channel blockers. This represents a pharmacodynamic, and not a pharmacokinetic, interaction. Close monitoring of blood pressure, especially in patients who are taking antihypertensive agents, may be needed
    Betaxolol: (Moderate) Oral calcium-channel blockers and beta-blockers like betaxolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Betrixaban: (Major) Avoid betrixaban use in patients with severe renal impairment receiving verapamil. Reduce betrixaban dosage to 80 mg PO once followed by 40 mg PO once daily in all other patients receiving verapamil. Bleeding risk may be increased; monitor patients closely for signs and symptoms of bleeding. Betrixaban is a substrate of P-gp; verapamil inhibits P-gp.
    Bisoprolol: (Moderate) Oral calcium-channel blockers and beta-blockers like bisoprolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Bisoprolol; Hydrochlorothiazide, HCTZ: (Moderate) Oral calcium-channel blockers and beta-blockers like bisoprolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Boceprevir: (Moderate) Close clinical monitoring is advised when administering verapamil with boceprevir due to an increased potential for verapamil-related adverse events. If verapamil dose adjustments are made, re-adjust the dose upon completion of boceprevir treatment. Predictions about the interaction can be made based on the metabolic pathways of verapamil and boceprevir. Both verapamil and boceprevir are substrates and inhibitors of the hepatic isoenzyme CYP3A4 and the drug efflux transporter, P-glycoprotein (PGP). When used in combination, the plasma concentrations of both medications may be elevated.
    Bortezomib: (Moderate) Patients on antihypertensive agents receiving bortezomib treatment may require close monitoring of their blood pressure and dosage adjustment of their medication. During clinical trials of bortezomib, hypotension was reported in roughly 12 percent of patients.
    Bosentan: (Moderate) Although no specific interactions have been documented, bosentan has vasodilatory effects and may contribute additive hypotensive effects when given with angiotensin-converting enzyme inhibitors (ACE inhibitors). (Moderate) Although no specific interactions have been documented, bosentan has vasodilatory effects and may contribute additive hypotensive effects when given with calcium-channel blockers. In addition, bosentan may induce hepatic metabolism of calcium-channel blockers metabolized by CYP3A4 isoenzymes. Diltiazem and verapamil have potential to inhibit CYP3A4 metabolism of bosentan. Bosentan has been shown to have no pharmacokinetic interactions with nimodipine.
    Bosutinib: (Major) Avoid concomitant use of bosutinib and verapamil or as bosutinib plasma exposure may be significantly increased resulting in an increased risk of bosutinib adverse events (e.g., myelosuppression, GI toxicity). Bosutinib is a CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. In a cross-over trial in 18 healthy volunteers, the Cmax and AUC values of bosutinib were increased 1.5-fold and 2-fold, respectively, when bosutinib 500 mg PO was administered with a single dose of a moderate CYP3A4 inhibitor.
    Bretylium: (Major) Concomitant use of bretylium with other antiarrhythmics, such as verapamil, can have additive, antagonistic, or synergistic electrophysiologic, pharmacodynamic, or toxic effects, including hypotension. Combined antiarrhythmic therapy may necessitate a reduction in antiarrhythmic drug dosages, to decrease the potential for toxicity.
    Brexpiprazole: (Moderate) Because brexpiprazole is primarily metabolized by CYP3A4 and CYP2D6, systemic exposure may be increased during use of a moderate CYP3A4 inhibitor such as verapamil and careful monitoring is advisable. In addition, the manufacturer recommends that the brexpiprazole dose be reduced to one-quarter (25%) of the usual dose in patients receiving a moderate to strong inhibitor of CYP3A4 in combination with a moderate to strong inhibitor of CYP2D6. If verapamil is used in combination with brexpiprazole and a moderate to strong CYP2D6 inhibitor, the brexpiprazole dose should be adjusted and the patient should be carefully monitored for brexpiprazole-related adverse reactions. (Moderate) Due to brexpiprazole's antagonism at alpha 1-adrenergic receptors, the drug may enhance the hypotensive effects of alpha-blockers and other antihypertensive agents.
    Brigatinib: (Moderate) Monitor for decreased efficacy of verapamil if coadministration with brigatinib is necessary. Verapamil is a CYP3A substrate and brigatinib induces CYP3A in vitro; plasma concentrations of verapamil may decrease.
    Brimonidine; Timolol: (Moderate) Oral calcium-channel blockers and beta-blockers like timolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Bromocriptine: (Major) When bromocriptine is used for diabetes, do not exceed a dose of 1.6 mg once daily during concomitant use of verapamil. Use this combination with caution in patients receiving bromocriptine for other indications. Concurrent use may increase bromocriptine concentrations. Additionally, bromocriptine should be used cautiously with other medications known to lower blood pressure such as verapamil. Monitoring of blood pressure should be considered, especially during the initial weeks of therapy or during dose increases. Bromocriptine is extensively metabolized in the liver via CYP3A4; verapamil is a moderate inhibitor of CYP3A4. Administration of bromocriptine with a moderate inhibitor of CYP3A4 increased the bromocriptine mean AUC and Cmax by 3.7-fold and 4.6-fold, respectively. (Minor) Bromocriptine has only minimal affinity for adrenergic receptors; however, hypotension can occur during bromocriptine administration. Orthostatic hypotension occurs in 6% of acromegaly patients receiving the drug. Hypotension occurred frequently (approximately 30%) in postpartum studies, which in rare cases approached a decline in supine pressure of almost 60 mmHg. It is unknown if bromocriptine is the exact cause of this effect. However, the drug should be used cautiously with other medications known to lower blood pressure such as antihypertensive agents. Monitoring of blood pressure should be considered, especially during the initial weeks of concomitant therapy.
    Brompheniramine; Carbetapentane; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Brompheniramine; Guaifenesin; Hydrocodone: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects.
    Brompheniramine; Hydrocodone; Pseudoephedrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Brompheniramine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Budesonide: (Moderate) Avoid coadministration of oral budesonide and verapamil due to the potential for increased budesonide exposure. Use caution with inhaled forms of budesonide as systemic exposure to the corticosteroid may also increase. Budesonide is a CYP3A4 substrate; verapamil a weak CYP3A4 inhibitor and the active metabolite norverapamil is a moderate CYP3A4 inhibitor. In the presence of a strong CYP3A4 inhibitor, the systemic exposure to oral budesonide was increased by 8-fold.
    Budesonide; Formoterol: (Moderate) Avoid coadministration of oral budesonide and verapamil due to the potential for increased budesonide exposure. Use caution with inhaled forms of budesonide as systemic exposure to the corticosteroid may also increase. Budesonide is a CYP3A4 substrate; verapamil a weak CYP3A4 inhibitor and the active metabolite norverapamil is a moderate CYP3A4 inhibitor. In the presence of a strong CYP3A4 inhibitor, the systemic exposure to oral budesonide was increased by 8-fold.
    Bupivacaine Liposomal: (Moderate) Verapamil may inhibit the CYP3A4-mediated metabolism of and bupivacaine. Use caution when administering these drugs concomitantly.
    Bupivacaine: (Moderate) Verapamil may inhibit the CYP3A4-mediated metabolism of and bupivacaine. Use caution when administering these drugs concomitantly.
    Bupivacaine; Lidocaine: (Moderate) Concomitant use of systemic lidocaine and verapamil may increase lidocaine plasma concentrations by decreasing lidocaine clearance and therefore prolonging the elimination half-life. Monitor for lidocaine toxicity if used together. Lidocaine is a CYP3A4 and CYP1A2 substrate; verapamil inhibits both hepatic isoenzymes. (Moderate) Verapamil may inhibit the CYP3A4-mediated metabolism of and bupivacaine. Use caution when administering these drugs concomitantly.
    Buprenorphine: (Moderate) Verapamil is an inhibitor of CYP3A4 isoenzymes. Co-administration with verapamil may lead to an increase in serum levels of drugs that are CYP3A4 substrates, such as buprenorphine.
    Buprenorphine; Naloxone: (Moderate) Verapamil is an inhibitor of CYP3A4 isoenzymes. Co-administration with verapamil may lead to an increase in serum levels of drugs that are CYP3A4 substrates, such as buprenorphine.
    Buspirone: (Moderate) Coadministration of buspirone with verapamil substantially increases the plasma concentrations of buspirone by about three-fold. The mechanism is probably related to the inhibition of CYP3A4 by verapamil. Buspirone dose adjustment may be necessary and should be based on clinical assessment.
    Butabarbital: (Major) Barbiturates have been shown to enhance the hepatic clearance of verapamil. The effect on oral verapamil is greater than for IV verapamil, but a significant increase in clearance has been noted for both verapamil dosage forms during concomitant administration of a barbiturate. Patients receiving verapamil should be monitored for loss of therapeutic effect if barbiturates are added.
    Cabazitaxel: (Minor) Cabazitaxel is a CYP3A4 and P-glycoprotein (P-gp) substrate; verapamil is a moderate inhibitor of CYP3A4 as well as a P-gp inhibitor. A drug interaction study with repeated administration of aprepitant, another moderate CYP3A4 inhibitor, did not modify the exposure to cabazitaxel; however, formal drug interaction studies have not been conducted with P-gp inhibitors. Use caution when cabazitaxel is administered concomitantly with P-gp inhibitors.
    Cabergoline: (Major) Cabergoline has been associated with hypotension in some instances. Cabergoline should be used cautiously in those receiving antihypertensive agents. Also, Verapamil is an inhibitor of CYP3A4 isoenzymes and may decrease the metabolism of ergot alkaloids. (Minor) Cabergoline has minimal affinity for adrenergic receptors; however, it has been associated with hypotension in some instances. Cabergoline should be used cautiously in those receiving antihypertensive agents.
    Cabozantinib: (Moderate) Monitor for an increase in cabozantinib- and verapamil-related adverse events if concomitant use of cabozantinib and verapamil is necessary. Cabozantinib is primarily metabolized by CYP3A4 and verapamil is a CYP3A4 inhibitor. Coadministration with a strong CYP3A4 inhibitor, ketoconazole (400 mg daily for 27 days), increased cabozantinib (single dose) exposure by 38%. The manufacturer of cabozantinib recommends a dose reduction when used with strong CYP3A4 inhibitors; however, recommendations are not available for concomitant use with a moderate inhibitor of CYP3A4. Cabozantinib is also a P-glycoprotein (P-gp) inhibitor and verapamil is a substrate of P-gp; plasma concentrations of verapamil may be increased. However, the clinical relevance of this finding is unknown.
    Caffeine: (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Caffeine; Ergotamine: (Major) Because of the potential to cause coronary vasospasm , ergotamine theoretically could antagonize the therapeutic effects of calcium-channel blockers. Clinicians should also note that calcium-channel blockers with CYP3A4 inhibitory properties, such as diltiazem, nicardipine, and verapamil, may also reduce the hepatic metabolism of ergotamine and increase the risk of ergot toxicity. (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products to minimize caffeine-related side effects.
    Calcium Phosphate, Supersaturated: (Moderate) Concomitant use of medicines with potential to alter renal perfusion or function such as angiotensin-converting enzyme inhibitors, may increase the risk of acute phosphate nephropathy in patients taking sodium phosphate monobasic monohydrate; sodium phosphate dibasic anhydrous.
    Canagliflozin: (Moderate) When canagliflozin is initiated in patients already receiving angiotensin-converting enzyme inhibitors (ACE inhibitors), symptomatic hypotension can occur. Patients with impaired renal function (eGFR < 60 ml/min/1.73 m2), low systolic blood pressure, or who are elderly may also be at a greater risk. Before initiating canagliflozin in patients with one or more of these characteristics, volume status should be assessed and corrected. Monitor for signs and symptoms after initiating therapy. In addition, canagliflozin can lead to hyperkalemia. Patients treated with canagliflozin 300 mg/day were more likely to experience increases in potassium. Patients with moderate renal impairment who are taking medications that interfere with potassium excretion, such as medications that interfere with the renin-angiotensin-aldosterone (RAA) system, are more likely to develop hyperkalemia. Monitor serum potassium levels periodically after initiating canagliflozin in patients with impaired renal function and in patients predisposed to hyperkalemia due to medications or other medical conditions.
    Canagliflozin; Metformin: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) When canagliflozin is initiated in patients already receiving angiotensin-converting enzyme inhibitors (ACE inhibitors), symptomatic hypotension can occur. Patients with impaired renal function (eGFR < 60 ml/min/1.73 m2), low systolic blood pressure, or who are elderly may also be at a greater risk. Before initiating canagliflozin in patients with one or more of these characteristics, volume status should be assessed and corrected. Monitor for signs and symptoms after initiating therapy. In addition, canagliflozin can lead to hyperkalemia. Patients treated with canagliflozin 300 mg/day were more likely to experience increases in potassium. Patients with moderate renal impairment who are taking medications that interfere with potassium excretion, such as medications that interfere with the renin-angiotensin-aldosterone (RAA) system, are more likely to develop hyperkalemia. Monitor serum potassium levels periodically after initiating canagliflozin in patients with impaired renal function and in patients predisposed to hyperkalemia due to medications or other medical conditions.
    Candesartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Candesartan; Hydrochlorothiazide, HCTZ: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Carbamazepine: (Moderate) Carbamazepine and verapamil are metabolized by hepatic isozyme CYP3A4. Verapamil, a CYP3A4 inhibitor, may decrease the metabolism of carbamazepine. Consider dose reduction of carbamazepine if verapamil is added. In theory, carbamazepine can reduce verapamil oral bioavailability by accelerating its CYP3A4 metabolism.
    Carbetapentane; Chlorpheniramine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbetapentane; Diphenhydramine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbetapentane; Guaifenesin; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbetapentane; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbetapentane; Phenylephrine; Pyrilamine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbetapentane; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Carbidopa; Levodopa: (Moderate) Concomitant use of antihypertensive agents with levodopa can result in additive hypotensive effects. (Moderate) Concomitant use of antihypertensive agents with levodopa can result in additive hypotensive effects.
    Carbidopa; Levodopa; Entacapone: (Moderate) Concomitant use of antihypertensive agents with levodopa can result in additive hypotensive effects. (Moderate) Concomitant use of antihypertensive agents with levodopa can result in additive hypotensive effects.
    Carbinoxamine; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Carbinoxamine; Hydrocodone; Phenylephrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbinoxamine; Hydrocodone; Pseudoephedrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Carbinoxamine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Carbinoxamine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Cariprazine: (Moderate) Cariprazine and its active metabolites are extensively metabolized by CYP3A4. Verapamil is a moderate inhibitor of CYP3A4 and may reduce the hepatic metabolism of CYP3A4 substrates, although the impact of moderate CYP3A4 inhibitors on cariprazine metabolism has not been studied. Monitoring for adverse effects, such as CNS effects and extrapyramidal symptoms, is advisable during coadministration. In addition, orthostatic vital signs should be monitored in patients who are at risk for hypotension, such as those receiving cariprazine in combination with antihypertensive agents. Atypical antipsychotics may cause orthostatic hypotension and syncope, most commonly during treatment initiation and dosage increases. Patients should be informed about measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning, or rising slowly from a seated position. Consider a cariprazine dose reduction if hypotension occurs. (Moderate) Orthostatic vital signs should be monitored in patients who are at risk for hypotension, such as those receiving cariprazine in combination with antihypertensive agents. Atypical antipsychotics may cause orthostatic hypotension and syncope, most commonly during treatment initiation and dosage increases. Patients should be informed about measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning, or rising slowly from a seated position. Consider a cariprazine dose reduction if hypotension occurs.
    Carteolol: (Moderate) Oral calcium-channel blockers and beta-blockers like carteolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Carvedilol: (Moderate) Oral calcium-channel blockers and beta-blockers like carvedilol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Celecoxib: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Ceritinib: (Major) Avoid coadministration of ceritinib with verapamil due to the risk of additive bradycardia and increased verapamil exposure. If unavoidable, monitor heart rate and blood pressure regularly. An interruption of ceritinib therapy, dose reduction, or discontinuation of therapy may be necessary. Ceritinib is a CYP3A4 inhibitor and verapamil is primarily metabolized by CYP3A4.
    Cerivastatin: (Severe) Verapamil may increase the serum concentrations of cerivastatin which is a CYP3A4 substrate. The interaction is presumed due to increased cerivastatin bioavailability via inhibition of CYP3A4 metabolism and reduction of first-pass metabolism.
    Cetirizine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Cevimeline: (Moderate) Cevimeline is metabolized by cytochrome P450 CYP3A4 and CYP2D6. In theory, concurrent administration of inhibitors of CYP3A4, such as verapamil, may lead to increased cevimeline plasma concentrations.
    Chlophedianol; Dexchlorpheniramine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Chlophedianol; Guaifenesin; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Chlordiazepoxide: (Moderate) Verapamil is a CYP3A4 inhibitor and may reduce the metabolism of chlordiazepoxide and increase the potential for benzodiazepine toxicity.
    Chlordiazepoxide; Clidinium: (Moderate) Verapamil is a CYP3A4 inhibitor and may reduce the metabolism of chlordiazepoxide and increase the potential for benzodiazepine toxicity.
    Chloroprocaine: (Moderate) Local anesthetics may cause additive hypotension in combination with antihypertensive agents. (Moderate) Local anesthetics may cause additive hypotension in combination with antihypertensive agents.
    Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Chlorpheniramine; Dihydrocodeine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Chlorpheniramine; Guaifenesin; Hydrocodone; Pseudoephedrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Chlorpheniramine; Hydrocodone: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects.
    Chlorpheniramine; Hydrocodone; Phenylephrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Chlorpheniramine; Hydrocodone; Pseudoephedrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Chlorpheniramine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Chlorpheniramine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Chlorthalidone; Clonidine: (Moderate) Complete AV block resulting in a nodal rhythm and sinus bradycardia resulting in hospitalization and pacemaker insertion have been reported during combination therapy of clonidine with diltiazem or verapamil. Monitor heart rate in patients receiving concomitant clonidine and verapamil which is known to affect sinus node function or AV nodal conduction.
    Cilostazol: (Major) Cilostazol clearance may be impaired by inhibitors of the CYP3A4 hepatic microsomal isoenzyme, including verapamil. When verapamil is coadministered with cilostazol, the manufacturer recommends that the cilostazol dosage be reduced by 50%.
    Cimetidine: (Moderate) Cimetidine is a potent inhibitor of many of the isoenzymes of the hepatic CYP450 oxidative enzyme system. The metabolism of calcium-channel blockers like verapamil is inhibited by cimetidine.
    Cinacalcet: (Major) Cinacalcet is metabolized primarily by the CYP3A4 isoenzyme. Subjects being treated with 200 mg ketoconazole twice daily for 7 days received a single 90 mg cinacalcet dose on day 5 of therapy. The AUC and Cmax for cinacalcet increased 2.3 to 2.2 times, respectively, compared to 90 mg cinacalcet given alone. Therefore, caution is recommended when co-administering cinacalcet with other CYP3A4 enzyme inhibitors. These agents may include verapamil. If a patient initiates or discontinues therapy with a strong CYP3A4 inhibitor during cinacalcet therapy, the manufacturer recommends that dosage adjustment may be needed with close monitoring of PTH and serum calcium concentrations.
    Cisapride: (Severe) Postmarketing surveillance reports have documented QT prolongation and ventricular arrhythmias, including torsade de pointes and death, when known and potent inhibitors of CYP3A4 are coadministered with cisapride. Verapamil may have the potential to inhibit the metabolism of cisapride through CYP3A4 and thus, should not be used with cisapride.
    Cisplatin: (Minor) The absorption of verapamil can be reduced by the vindesine, doxorubicin, cisplatin (VAC) chemotherapeutic drug regimen.
    Citalopram: (Moderate) During concurrent use of citalopram and verapamil, clinicians should monitor patients for a potential increase in side effects or toxicity. In theory, verapamil may inhibit the metabolism of citalopram through inhibition of CYP3A4. It should be noted that because citalopram is metabolized by multiple enzyme systems, inhibition of one pathway may not appreciably decrease citalopram clearance.
    Clarithromycin: (Major) Coadministration of clarithromycin and calcium-channel blockers should be avoided if possible, particularly in geriatric patients, due to an increased risk of hypotension and acute kidney injury. Most reports of acute kidney injury were with the combination of clarithromycin with calcium channel blockers metabolized by CYP3A4 and involved elderly patients at least 65 years of age. Clarithromycin may decrease the clearance of calcium-channel blockers (e.g., amlodipine, diltiazem, felodipine, nifedipine, and verapamil) via inhibition of CYP3A4 metabolism. A retrospective, case crossover study, found the risk of hospitalization due to hypotension or shock to be significantly increased in geriatric patients exposed to clarithromycin during concurrent calcium-channel blocker therapy (OR 3.7, 95% CI 2.3-6.1). Concurrent use of azithromycin was not associated with an increased risk of hypotension (OR 1.5, 95% CI 0.8-2.8). One case of a possible verapamil-clarithromycin interaction was reported, which was associated with hypotension. If the use of a macrolide antibiotic is necessary in a patient receiving calcium-channel blocker therapy, azithromycin is the preferred agent.
    Clindamycin: (Moderate) Concomitant use of clindamycin and verapamil may decrease clindamycin clearance and increase the risk of adverse reactions. Clindamycin is a CYP3A4 substrate; verapamil is a moderate inhibitor of CYP3A4. Caution and close monitoring are advised if these drugs are used together.
    Clofarabine: (Moderate) Concomitant use of clofarabine, a substrate of OCT1, and verapamil, an inhibitor of OCT1, may result in increased clofarabine levels. Therefore, monitor for signs of clofarabine toxicity such as gastrointestinal toxicity (e.g., nausea, vomiting, diarrhea, mucosal inflammation), hematologic toxicity, and skin toxicity (e.g. hand and foot syndrome, rash, pruritus) in patients also receiving OCT1 inhibitors.
    Clonazepam: (Moderate) CYP3A4 inhibitors, such as verapamil, may reduce the metabolism of clonazepam and increase the potential for benzodiazepine toxicity.
    Clonidine: (Moderate) Complete AV block resulting in a nodal rhythm and sinus bradycardia resulting in hospitalization and pacemaker insertion have been reported during combination therapy of clonidine with diltiazem or verapamil. Monitor heart rate in patients receiving concomitant clonidine and verapamil which is known to affect sinus node function or AV nodal conduction.
    Clorazepate: (Moderate) CYP3A4 inhibitors, such as verapamil, may reduce the metabolism of clorazepate and increase the potential for benzodiazepine toxicity.
    Clozapine: (Moderate) Caution is advisable during concurrent use of verapamil and clozapine. Verapamil is an inhibitor of CYP3A4, one of the isoenzymes responsible for the metabolism of clozapine. Treatment with clozapine has been associated with QT prolongation, torsade de pointes (TdP), cardiac arrest, and sudden death. Elevated plasma concentrations of clozapine occurring through CYP inhibition may potentially increase the risk of life-threatening arrhythmias, sedation, anticholinergic effects, seizures, orthostasis, or other adverse effects. According to the manufacturer, patients receiving clozapine in combination with an inhibitor of CYP3A4 should be monitored for adverse reactions. Consideration should be given to reducing the clozapine dose if necessary. If the inhibitor is discontinued after dose adjustments are made, monitor for lack of clozapine effectiveness and consider increasing the clozapine dose if necessary. (Moderate) Lisinopril may decrease the renal elimination of clozapine and metabolites. Clozapine toxicity, including irritability, anger, insomnia, nightmares and sialorrhea may occur. The mechanism of this interaction is unclear; however, as lisinopril does not undergo metabolism, cytochrome P450 enzyme involvement is unlikely. It is speculated that a decrease in renal elimination of clozapine occurs due to a lisinopril-induced reduction in glomerular filtration rate (GFR). Plasma clozapine concentrations should be measured carefully during concomitant lisinopril therapy; another antihypertensive class may need to be selected. In addition, clozapine used concomitantly with the antihypertensive agents can increase the risk and severity of hypotension by potentiating the effect of the antihypertensive drug.
    Cobicistat: (Moderate) Coadministration of cobicistat (a CYP3A4 inhibitor) with calcium-channel blockers metabolized by CYP3A4, such as verapamil, may result in elevated calcium-channel blockers serum concentrations. If used concurrently, close clinical monitoring with appropriate dose reductions are advised.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Alafenamide: (Moderate) Coadministration of cobicistat (a CYP3A4 inhibitor) with calcium-channel blockers metabolized by CYP3A4, such as verapamil, may result in elevated calcium-channel blockers serum concentrations. If used concurrently, close clinical monitoring with appropriate dose reductions are advised. (Moderate) Coadministration of verapamil and tenofovir alafenamide may result in elevated tenofovir concentrations. Verapamil is an inhibitor of the drug transporter P-glycoprotein (P-gp). Tenofovir alafenamide is a substrate for P-gp. Of note, when tenofovir alafenamide is administered as part of a cobicistat-containing product, its availability is increased by cobicistat and a further increase of tenofovir alafenamide concentrations is not expected upon coadministration of an additional P-gp inhibitor.
    Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Disoproxil Fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as verapamil. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions. (Moderate) Coadministration of cobicistat (a CYP3A4 inhibitor) with calcium-channel blockers metabolized by CYP3A4, such as verapamil, may result in elevated calcium-channel blockers serum concentrations. If used concurrently, close clinical monitoring with appropriate dose reductions are advised.
    Cobimetinib: (Major) Avoid the concurrent use of cobimetinib with chronic verapamil therapy due to the risk of cobimetinib toxicity. If concurrent short-term (14 days or less) use of verapamil is unavoidable, reduce the dose of cobimetinib to 20 mg once daily for patients normally taking 60 mg daily; after discontinuation of verapamil, resume cobimetinib at the previous dose. Use an alternative to verapamil in patients who are already taking a reduced dose of cobimetinib (40 or 20 mg daily). Cobimetinib is a P-glycoprotein (P-gp) substrate as well as a CYP3A substrate in vitro; verapamil is a moderate inhibitor of both CYP3A and P-gp. In healthy subjects (n = 15), coadministration of a single 10 mg dose of cobimetinib with itraconazole (200 mg once daily for 14 days), a strong CYP3A4 inhibitor, increased the mean cobimetinib AUC by 6.7-fold (90% CI, 5.6 to 8) and the mean Cmax by 3.2-fold (90% CI, 2.7 to 3.7).
    Cod Liver Oil: (Moderate) Fish oil supplements may cause mild, dose-dependent reductions in systolic or diastolic blood pressure in untreated hypertensive patients. Relatively high doses of fish oil are required to produce any blood pressure lowering effect. Additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents. (Moderate) Fish oil supplements may cause mild, dose-dependent reductions in systolic or diastolic blood pressure in untreated hypertensive patients. Relatively high doses of fish oil are required to produce any blood pressure lowering effect. Additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents. (Moderate) High doses of fish oil supplements may produce a blood pressure lowering effect. It is possible that additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents. (Moderate) High doses of fish oil supplements may produce a blood pressure lowering effect. It is possible that additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents.
    Codeine; Phenylephrine; Promethazine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Co-Enzyme Q10, Ubiquinone: (Moderate) Co-enzyme Q10, ubiquinone (CoQ10) may lower blood pressure. CoQ10 use in combination with antihypertensive agents may lead to additional reductions in blood pressure in some individuals. Patients who choose to take CoQ10 concurrently with antihypertensive medications should receive periodic blood pressure monitoring. Patients should be advised to inform their prescriber of their use of CoQ10.
    Colchicine: (Major) Due to the risk for serious colchicine toxicity including multi-organ failure and death, avoid coadministration of colchicine and verapamil in patients with normal renal and hepatic function unless the use of both agents is imperative. Coadministration is contraindicated in patients with renal or hepatic impairment because colchicine accumulation may be greater in these populations. Verapamil can inhibit colchicine's metabolism via P-glycoprotein (P-gp) and CYP3A4, resulting in increased colchicine exposure. If coadministration in patients with normal renal and hepatic function cannot be avoided, adjust the dose of colchicine by either reducing the daily dose or the dosage frequency, and carefully monitor for colchicine toxicity. Specific dosage adjustment recommendations are available for the Colcrys product for patients who have taken verapamil in the past 14 days or require concurrent use: for prophylaxis of gout flares, if the original dose is 0.6 mg twice daily, decrease to 0.3 mg twice daily or 0.6 mg once daily or if the original dose is 0.6 mg once daily, decrease the dose to 0.3 mg once daily; for treatment of gout flares, give 1.2 mg as a single dose and do not repeat for at least 3 days; for familial Mediterranean fever, do not exceed 1.2 mg/day.
    Colesevelam: (Moderate) Colesevelam may significantly decrease the Cmax and AUC of sustained-release verapamil. The clinical significance of this interaction is not known since verapamil bioavailability is highly variable.
    Conivaptan: (Major) Avoid concomitant use of conivaptan, a CYP3A4/P-glycoprotein (P-gp) inhibitor and CYP3A4 substrate, and verapamil, a CYP3A4/P-gp substrate and CYP3A4 inhibitor. Coadministration may result in elevated concentrations of both conivaptan and verapamil. According to the manufacturer of conivaptan, concomitant use of conivaptan with drugs that are primarily metabolized by CYP3A4, such as verapamil, should be avoided. Subsequent treatment with CYP3A substrates may be initiated no sooner than 1 week after completion of conivaptan therapy. Based on the pharmacology of conivaptan, there is potential for additive hypotensive effects when coadministered with calcium-channel blockers. Intravenous infusion of conivaptan has been associated with orthostatic hypotension. Monitor blood pressure and fluid volume status closely in patients receiving conivaptan infusion. (Moderate) There is potential for additive hypotensive effects when conivaptan is coadministered with antihypertensive agents.
    Conjugated Estrogens: (Minor) Estrogens are partially metabolized by CYP3A4. Drugs that inhibit CYP3A4 such as verapamil may increase plasma concentrations of estrogens and cause estrogen-related side effects such as nausea and breast tenderness. Patients receiving estrogens should be monitored for an increase in adverse events.
    Conjugated Estrogens; Bazedoxifene: (Minor) Estrogens are partially metabolized by CYP3A4. Drugs that inhibit CYP3A4 such as verapamil may increase plasma concentrations of estrogens and cause estrogen-related side effects such as nausea and breast tenderness. Patients receiving estrogens should be monitored for an increase in adverse events.
    Conjugated Estrogens; Medroxyprogesterone: (Minor) Estrogens are partially metabolized by CYP3A4. Drugs that inhibit CYP3A4 such as verapamil may increase plasma concentrations of estrogens and cause estrogen-related side effects such as nausea and breast tenderness. Patients receiving estrogens should be monitored for an increase in adverse events.
    Crizotinib: (Moderate) Monitor blood pressure and heart rate, as well as monitoring for an increase in crizotinib-related adverse reactions, if coadministration of verapamil with crizotinib is necessary. Both verapamil and crizotinib are CYP3A4 substrates and moderate CYP3A4 inhibitors.
    Cyclobenzaprine: (Major) Concurrent use of cyclobenzaprine with verapamil increases the possibility of developing serotonin syndrome. If these drugs must be used together, closely monitor the patient for signs and symptoms of serotonin syndrome. If such a reaction develops, immediately discontinue both drugs. Additionally, based on in vitro data the CYP3A4 enzyme and CYP1A2 enzyme are primarily responsible for the hepatic metabolism of cyclobenzaprine. Concentrations of cyclobenzaprine could increase if used in combination with CYP3A4 inhibitors such as verapamil. Observe the patient for enhanced side effects, such as CNS depression, if these drugs are coadministered.
    Cyclophosphamide: (Moderate) Use caution if cyclophosphamide is used concomitantly with angiotensin-converting enzyme inhibitors (ACE inhibitors), as increased or additive leukopenia may occur. (Moderate) Use caution if cyclophosphamide is used concomitantly with verapamil, and monitor for possible changes in the efficacy or toxicity profile of cyclophosphamide or a loss of blood pressure control. The clinical significance of this interaction is unknown. The absorption of verapamil can be reduced by the cyclophosphamide, vincristine, procarbazine, prednisone (COPP) chemotherapeutic drug regimen. Also, cyclophosphamide is a prodrug that is hydroxylated and activated primarily by CYP2B6; the contribution of CYP3A4 to the activation of cyclophosphamide is variable. Additional isoenzymes involved in the activation of cyclophosphamide include CYP2A6, 2C9, 2C18, and 2C19. N-dechloroethylation to therapeutically inactive but neurotoxic metabolites occurs primarily via CYP3A4. The active metabolites, 4-hydroxycyclophosphamide and aldophosphamide, are then inactivated by aldehyde dehydrogenase-mediated oxidation. Verapamil is a moderate CYP3A4 inhibitor; conversion of cyclophosphamide to its active metabolites may be affected. In vitro, coadministration with troleandomycin, a CYP3A4 inhibitor, had little-to-no effect on cyclophosphamide metabolism. However, concurrent use of cyclophosphamide conditioning therapy with itraconazole (a strong CYP3A4 inhibitor) and fluconazole (a moderate CYP3A4 inhibitor) in a randomized trial resulted in increases in serum bilirubin and creatinine, along with increased exposure to toxic cyclophosphamide metabolites (n = 197).
    Cyclosporine: (Moderate) Coadministration of verapamil with cyclosporine can lead to increased cyclosporine concentrations and toxicity. Verapamil inhibits CYP3A4 metabolism and thereby can increase the serum concentrations of cyclosporine. Verapamil should be used cautiously in patients stabilized on cyclosporine; cyclosporine dosage reduction may be required. (Moderate) Several cases of acute renal failure have been associated with the addition of angiotensin-converting enzyme (ACE) inhibitors to cyclosporine therapy in renal transplant patients. In response to cyclosporine-induced renal afferent vasoconstriction and glomerular hypoperfusion, angiotensin II is required to maintain an adequate glomerular filtration rate. Inhibition of ACE could reduce renal function acutely. Also, cyclosporine can cause hyperkalemia, and inhibition of angiotensin II leads to reduced aldosterone concentrations, which can increase the serum potassium concentration. Closely monitor renal function and serum potassium concentrations in patients receiving cyclosporine concurrently with ACE inhibitors or potassium salts.
    Dabigatran: (Moderate) Increased serum concentrations of dabigatran are possible when dabigatran, a P-glycoprotein (P-gp) substrate, is coadministered with verapamil, a P-gp inhibitor. Patients should be monitored for increased adverse effects of dabigatran while taking products containing verapamil including trandolapril; verapamil. When dabigatran is administered for treatment or reduction in risk of recurrence of deep venous thrombosis (DVT) or pulmonary embolism (PE) or prophylaxis of DVT or PE following hip replacement surgery, avoid coadministration with P-gp inhibitors like verapamil in patients with CrCl less than 50 mL/minute. When dabigatran is used in patients with non-valvular atrial fibrillation and severe renal impairment (CrCl less than 30 mL/minute), avoid coadministration with verapamil, as serum concentrations of dabigatran are expected to be higher than when administered to patients with normal renal function. Concomitant administration of verapamil and dabigatran results in an increased Cmax and AUC of dabigatran; the extent depends on the formulation of verapamil and timing of administration. The greatest increase in exposure of dabigatran occurs when verapamil is present in the gut when dabigatran is taken. In a pharmacokinetic study, immediate-release verapamil given 1 hour prior to dabigatran administration produced the greatest increase in exposure. If verapamil is administered 2 hours after dabigatran administration, the increase in AUC is negligible. Data from the RE-LY trial indicate no significant changes in dabigatran trough concentrations were seen in patients who received concomitant therapy with verapamil. P-gp inhibition and renal impairment are the major independent factors that result in increased exposure to dabigatran.
    Daclatasvir: (Moderate) Concurrent administration of daclatasvir, a CYP3A4 substrate, with verapamil, a moderate CYP3A4 inhibitor, may increase daclatasvir serum concentrations. In addition, the therapeutic effects of verapamil, a P-glycoprotein (P-gp) substrate, may be increased by daclatasvir, a P-gp inhibitor. If these drugs are administered together, monitor patients for adverse effects, such as hypotension, headache, fatigue, nausea, and diarrhea. The manufacturer does not recommend daclatasvir dose reduction for adverse reactions.
    Dalfopristin; Quinupristin: (Moderate) Dalfopristin; quinupristin is a major inhibitor of cytochrome P450 3A4 and may decrease the elimination of drugs metabolized by this enzyme including verapamil.
    Danazol: (Minor) Danazol is a CYP3A4 inhibitor and can decrease the hepatic metabolism of CYP3A4 substrates like calcium-channel blockers.
    Dantrolene: (Moderate) Concurrent use with skeletal muscle relaxants and antihypertensive agents may result in additive hypotension. Dosage adjustments of the antihypertensive medication may be required.
    Dapagliflozin: (Moderate) ACE inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors (i.e., captopril or enalapril) are administered concomitantly. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control.
    Dapagliflozin; Metformin: (Moderate) ACE inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors (i.e., captopril or enalapril) are administered concomitantly. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Dapagliflozin; Saxagliptin: (Moderate) ACE inhibitors may enhance the hypoglycemic effects antidiabetic agents by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. In addition, coadministration may increase the risk for angioedema. (Moderate) ACE inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors (i.e., captopril or enalapril) are administered concomitantly. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. (Minor) Saxagliptin plasma concentrations are expected to increase in the presence of moderate CYP 3A4/5 inhibitors such as verapamil, but saxagliptin dose adjustment is not advised.
    Darifenacin: (Moderate) Verapamil is an inhibitor of CYP3A4 isoenzymes. Co-administration with verapamil may lead to an increase in serum levels of drugs that are CYP3A4 substrates, including darifenacin.
    Darunavir: (Moderate) As darunavir is a CYP3A substrate and inhibitor, interactions with calcium-channel blockers may occur. Complex interactions can be expected with coadministered with diltiazem or verapamil, as both are substrates and inhibitors of CYP3A4.
    Darunavir; Cobicistat: (Moderate) As darunavir is a CYP3A substrate and inhibitor, interactions with calcium-channel blockers may occur. Complex interactions can be expected with coadministered with diltiazem or verapamil, as both are substrates and inhibitors of CYP3A4. (Moderate) Coadministration of cobicistat (a CYP3A4 inhibitor) with calcium-channel blockers metabolized by CYP3A4, such as verapamil, may result in elevated calcium-channel blockers serum concentrations. If used concurrently, close clinical monitoring with appropriate dose reductions are advised.
    Dasabuvir; Ombitasvir; Paritaprevir; Ritonavir: (Moderate) Concurrent administration of verapamil with dasabuvir; ombitasvir; paritaprevir; ritonavir may result in elevated plasma concentrations of all 5 drugs. A verapamil dose reduction and close monitoring for adverse events (i.e., hypotension and edema) are advised during coadministration. If adverse events are observed, consider further verapamil dose reductions or an alternative to the calcium channel blocker. Both verapamil and ritonavir are substrates and inhibitors of CYP3A4; paritaprevir and dasabuvir (minor) are partially metabolized by CYP3A4. Verapamil also inhibits the drug transporter P-glycoprotein (P-gp); dasabuvir, ombitasvir, paritaprevir and ritonavir are all substrates of P-gp. (Moderate) Concurrent administration of verapamil with dasabuvir; ombitasvir; paritaprevir; ritonavir or ombitasvir; paritaprevir; ritonavir may result in elevated plasma concentrations of both drugs. A verapamil dose reduction and close monitoring for adverse events (i.e., hypotension and edema) are advised during coadministration. If adverse events are observed, consider further verapamil dose reductions or an alternative to the calcium channel blocker. Both verapamil and ritonavir are substrates and inhibitors of CYP3A4; paritaprevir and dasabuvir (minor) are partially metabolized by CYP3A4. Verapamil also inhibits the drug transporter P-glycoprotein (P-gp); dasabuvir, ombitasvir, paritaprevir and ritonavir are all substrates of P-gp. (Moderate) Concurrent administration of verapamil with ritonavir may result in elevated plasma concentrations of both drugs. Both verapamil and ritonavir are substrates and inhibitors of CYP3A4. Verapamil also inhibits the drug transporter P-glycoprotein (P-gp); ritonavir is a substrate of P-gp. Ritonavir also prolongs the PR interval in some patients; however, the impact on the PR interval of coadministration of ritonavir with other drugs that prolong the PR interval (including calcium channel blockers) has not been evaluated. If coadministration of these drugs is warranted, do so with caution and careful monitoring. Decreased calcium-channel blocker doses may be warranted.
    Dasatinib: (Moderate) Dasatinib inhibits CYP3A4. Therefore, caution is warranted when drugs that are metabolized by this enzyme, such as calcium-channel blockers, are administered concurrently with dasatinib as increased adverse reactions may occur. Diltiazem, nicardipine and verapamil may also inhibit the metabolism of dasatinib.
    Deferasirox: (Moderate) Deferasirox inhibits CYP2C8. Verapamil is a substrate for CYP2C8. The concomitant administration of deferasirox and the CYP2C8 substrate repaglinide (single dose of 0.5 mg) resulted in an increase in repaglinide Cmax by 62% and an increase in AUC 2.3-fold. Although specific drug interaction studies of deferasirox and verapamil are not available, a similar interaction may occur. The dose of verapamil may need to be decreased if coadministered with deferasirox.
    Deflazacort: (Major) Decrease deflazacort dose to one third of the recommended dosage when coadministered with verapamil. Concurrent use may significantly increase concentrations of 21-desDFZ, the active metabolite of deflazacort, resulting in an increased risk of toxicity. Deflazacort is a CYP3A4 substrate; verapamil is a moderate inhibitor of CYP3A4. Administration of deflazacort with clarithromycin, a strong CYP3A4 inhibitor, increased total exposure to 21-desDFZ by about 3-fold.
    Delavirdine: (Moderate) Delavirdine is a potent inhibitor of the CYP3A4 and increased plasma concentrations of drugs extensively metabolized by this enzyme, such as verapamil, should be expected with concurrent use of delavirdine.
    Desloratadine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Dexchlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Dexmedetomidine: (Moderate) Concomitant administration of dexmedetomidine and calcium-channel blockers could lead to additive hypotension and bradycardia; use together with caution. Dexmedetomidine can produce bradycardia or AV block and should be used cautiously in patients who are receiving antihypertensive drugs that may lower the heart rate such as calcium-channel blockers.
    Dexmethylphenidate: (Moderate) Dexmethylphenidate can reduce the hypotensive effect of antihypertensive agents, including angiotensin-converting enzyme inhibitors (ACE inhibitors). Periodic evaluation of blood pressure is advisable during concurrent use of dexmethylphenidate and antihypertensive agents, particularly during initial coadministration and after dosage increases of dexmethylphenidate. (Moderate) Dexmethylphenidate can reduce the hypotensive effect of antihypertensive agents, including calcium-channel blockers. Periodic evaluation of blood pressure is advisable during concurrent use of dexmethylphenidate and antihypertensive agents, particularly during initial coadministration and after dosage increases of dexmethylphenidate.
    Dextromethorphan; Diphenhydramine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Dextromethorphan; Guaifenesin; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Dextromethorphan; Guaifenesin; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Dextromethorphan; Quinidine: (Major) Pharmacokinetic and pharmacodynamic interactions exist between quinidine and verapamil. Oral verapamil has been shown to reduce the clearance and metabolism of oral quinidine. Quinidine half-life increased and plasma concentrations were higher after verapamil. No changes in quinidine protein binding were observed. In addition to the pharmacokinetic interaction which may potentiate quinidine's clinical effects, both quinidine and verapamil can cause hypotension. When quinidine and verapamil are coadministered in doses that are each well tolerated as monotherapy, hypotension attributable to additive peripheral (alpha)-blockade is sometimes reported. Concurrent use of verapamil and quinidine in patients with hypertrophic cardiomyopathy or arrhythmias can cause significant hypotension. It is recommended to avoid combined therapy with verapamil and quinidine in patients with hypertrophic cardiomyopathy. Quinidine and verapamil may also have additive negative inotropic effects. Concurrent use of verapamil and quinidine should be monitored carefully for electrophysiologic and hemodynamic effects. (Moderate) Quinidine can decrease blood pressure and should be used cautiously in patients receiving antihypertensive agents due to the potential for additive hypotension.
    Diazepam: (Moderate) Verapamil inhibits CYP3A4 metabolism, and therefore may inhibit the metabolism of oxidized benzodiazepines, including diazepam.
    Diazoxide: (Moderate) Additive hypotensive effects can occur with the concomitant administration of diazoxide with other antihypertensive agents. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly. The manufacturer advises that IV diazoxide should not be administered to patients within 6 hours of receiving other antihypertensive agents. (Moderate) Additive hypotensive effects can occur with the concomitant administration of diazoxide with other antihypertensive agents. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly. The manufacturer advises that IV diazoxide should not be administered to patients within 6 hours of receiving other antihypertensive agents.
    Diclofenac: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Diclofenac; Misoprostol: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Dienogest; Estradiol valerate: (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Diethylpropion: (Major) Diethylpropion has vasopressor effects and may limit the benefit of angiotensin-converting enzyme inhibitors. Although leading drug interaction texts differ in the potential for an interaction between diethylpropion and this group of antihypertensive agents, these effects are likely to be clinically significant and have been described in hypertensive patients on these medications. (Major) Diethylpropion has vasopressor effects and may limit the benefit of calcium-channel blockers. Although leading drug interaction texts differ in the potential for an interaction between diethylpropion and this group of antihypertensive agents, these effects are likely to be clinically significant and have been described in hypertensive patients on these medications.
    Diflunisal: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Digoxin: (Major) Verapamil may reduce total body clearance and extrarenal clearance of digitoxin by 27% and 29%, respectively; serum concentrations of orally administered digoxin can increase by 50 to 75% during the first week of combination therapy, possibly resulting in digitalis toxicity. When verapamil is coadministered with intravenous (IV) digoxin, the digoxin AUC is increased by 24%. Measure serum digoxin concentrations before initiating verapamil. Reduce digoxin concentrations by decreasing the oral digoxin dose by approximately 30 to 50%, decreasing the IV digoxin dose by 15 to 30%, or by modifying the dosing frequency and continue monitoring. In addition to serum concentration information, the manufacturer of verapamil recommends adjusting the digoxin dosage according to clinical response, since digoxin serum concentrations may not accurately reflect response. Digoxin is a substrate for P-glycoprotein (P-gp). Verapamil inhibits P-gp, an energy-dependent cellular drug efflux pump. The inhibition of P-gp in the intestinal cell wall may lead to increased oral absorption of digoxin. It also has been shown that verapamil inhibits the secretion of digoxin by P-gp transporters in the kidney leading to decreased renal tubular elimination of digoxin and increased serum concentrations. Both drugs slow conduction through the AV node, and for this reason, these drugs are sometimes used together for ventricular control in patients with atrial fibrillation or flutter. In clinical trials in patients with atrial fibrillation or atrial flutter on both verapamil and digoxin, ventricular rates below 50/min at rest occurred in 15% of patients and asymptomatic hypotension occurred in 5% of patients. Additionally, the effect of verapamil on the pharmacokinetics of digoxin is magnified in patients with hepatic cirrhosis. (Moderate) Caution should be exercised when administering digoxin with drugs that may cause a significant deterioration in renal function including angiotensin-converting enzyme inhibitors (ACE inhibitors). A decline in glomerular filtration or tubular secretion may impair the excretion of digoxin. Close monitoring of serum digoxin concentrations is essential to avoid enhanced toxicity.
    Dihydrocodeine; Guaifenesin; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Dihydroergotamine: (Major) Because of the potential to cause coronary vasospasm, dihydroergotamine theoretically could antagonize the therapeutic effects of anti-anginal agents including calcium-channel blockers. Dihydroergotamine is contraindicated for use in patients with coronary heart disease or hypertension. Clinicians should also note that calcium-channel blockers with CYP3A4 inhibitory properties (e.g., diltiazem, nicardipine, verapamil) may also reduce the hepatic metabolism of dihydroergotamine and increase the risk of ergot toxicity.
    Diphenhydramine; Hydrocodone; Phenylephrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Diphenhydramine; Ibuprofen: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Diphenhydramine; Naproxen: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Diphenhydramine; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Disopyramide: (Severe) Disopyramide and verapamil should not be used concomitantly due to potential for additive negative inotropic effects which could result in left ventricular impairment. Avoid disopyramide administration within 48 hours before or 24 hours after verapamil administration. In addition, verapamil can theoretically inhibit the CYP3A4 metabolism of disopyramide.
    Dofetilide: (Severe) The concomitant use of verapamil (CYP3A4 inhibitor) and dofetilide is contraindicated. Coadministration of dofetilide with verapamil increased dofetilide peak plasma concentrations by 42%, although the overall exposure to dofetilide was not significantly increased. Concurrent use of verapamil and dofetilide was also associated with a higher occurrence of torsade de pointes in dofetilide clinical trials.
    Dolasetron: (Major) Use caution and monitor ECG if a drug known to prolong the PR interval (e.g., verapamil) is combined with dolasetron. Dolasetron has been associated with a dose-dependent prolongation in the QT, PR, and QRS intervals on an electrocardiogram. Concurrent use may result in additive effects.
    Dolutegravir; Rilpivirine: (Moderate) Close clinical monitoring is advised when administering verapamil with rilpivirine due to an increased potential for rilpivirine-related adverse events. Although this interaction has not been studied, predictions can be made based on metabolic pathways. Verapamil is an inhibitor of the hepatic isoenzyme CYP3A4; rilpivirine is metabolized by this isoenzyme. Coadministration may result in increased rilpivirine plasma concentrations.
    Donepezil: (Minor) Verapamil may inhibit the metabolism of donepezil by inhibiting CYP3A4. The clinical effect of this interaction on the response to donepezil has not been determined.
    Donepezil; Memantine: (Minor) Verapamil may inhibit the metabolism of donepezil by inhibiting CYP3A4. The clinical effect of this interaction on the response to donepezil has not been determined.
    Dorzolamide; Timolol: (Moderate) Oral calcium-channel blockers and beta-blockers like timolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Doxazosin: (Moderate) Additive pharmacodynamic effects are especially prominent when verapamil is co-administered with alpha-blockers. The use of alpha-blockers with verapamil can lead to excessive hypotension.
    Doxercalciferol: (Moderate) Cytochrome P450 enzyme inhibitors, such as verapamil, may inhibit the 25-hydroxylation of doxercalciferol, thereby decreasing the formation of the active metabolite and thus, decreasing efficacy.
    Doxorubicin: (Major) Avoid the concomitant use of doxorubicin and verapamil; use of these drugs together may increase doxorubicin concentrations and increase the risk of doxorubicin-induced toxicity. Doxorubicin is a substrate of CYP3A4 and P-glycoprotein (P-gp); verapamil is a substrate and inhibitor of CYP3A4 and P-gp.
    Dronabinol, THC: (Major) Use caution if coadministration of dronabinol with verapamil is necessary, and monitor for an increase in dronabinol-related adverse reactions (e.g., feeling high, dizziness, confusion, somnolence). Dronabinol is a CYP2C9 and 3A4 substrate; verapamil is a moderate inhibitor of CYP3A4. Concomitant use may result in elevated plasma concentrations of dronabinol.
    Dronedarone: (Major) Dronedarone is metabolized by CYP3A, is a moderate inhibitor of CYP3A, and is an inhibitor of P-gp. Diltiazem and verapamil are inhibitors of CYP3A4 and substrates of CYP3A and P-gp; nifedipine and amlodipine are substrates for CYP3A4. In clinical trials, the coadministration of dronedarone and calcium-channel blockers (diltiazem, verapamil, and nifedipine) resulted in an increase in exposure of calcium channel blockers by 1.4 to 1.5 fold and an increase in dronedarone exposure by 1.4 to1.7 fold. Furthermore, calcium channel blockers may potentiate the electrophysiologic effects of dronedarone (e.g., decreased AV and sinus node conduction). If coadministration of calcium channel blockers and dronedarone cannot be avoided, administer low doses of the calcium channel blocker and increase dosage only after ECG verification of tolerability.
    Drospirenone; Estradiol: (Moderate) Drospirenone has antimineralocorticoid effects and may increase serum potassium. The concurrent use of ACE inhibitors may increase the risk of hyperkalemia, especially in the presence of renal impairment. Monitor serum potassium during the 1st month of drospirenone treatment if an Angiotensin-Converting Enzyme inhibitor (ACE inhibitor) is used concurrently and thereafter as clinically indicated. Also monitor for any changes in blood pressure, fluid retention, or renal function. (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Drospirenone; Ethinyl Estradiol: (Moderate) Drospirenone has antimineralocorticoid effects and may increase serum potassium. The concurrent use of ACE inhibitors may increase the risk of hyperkalemia, especially in the presence of renal impairment. Monitor serum potassium during the 1st month of drospirenone treatment if an Angiotensin-Converting Enzyme inhibitor (ACE inhibitor) is used concurrently and thereafter as clinically indicated. Also monitor for any changes in blood pressure, fluid retention, or renal function. (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Drospirenone; Ethinyl Estradiol; Levomefolate: (Moderate) Drospirenone has antimineralocorticoid effects and may increase serum potassium. The concurrent use of ACE inhibitors may increase the risk of hyperkalemia, especially in the presence of renal impairment. Monitor serum potassium during the 1st month of drospirenone treatment if an Angiotensin-Converting Enzyme inhibitor (ACE inhibitor) is used concurrently and thereafter as clinically indicated. Also monitor for any changes in blood pressure, fluid retention, or renal function. (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Duloxetine: (Moderate) Orthostatic hypotension and syncope have been reported during duloxetine administration. The concurrent administration of antihypertensive agents and duloxetine may increase the risk of hypotension. Monitor blood pressure if the combination is necessary.
    Dutasteride: (Moderate) Dutasteride is metabolized by CYP3A4 enzyme. The clearance of dutasteride may be reduced when co-administered with the CYP3A4 inhibitor verapamil.
    Dutasteride; Tamsulosin: (Moderate) Dutasteride is metabolized by CYP3A4 enzyme. The clearance of dutasteride may be reduced when co-administered with the CYP3A4 inhibitor verapamil. (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Edoxaban: (Major) Reduce the dose of edoxaban to 30 mg/day PO in patients being treated for deep venous thrombosis (DVT) or pulmonary embolism and receiving concomitant therapy with verapamil. No dosage adjustment is required in patients with atrial fibrillation. Edoxaban is a P-glycoprotein (P-gp) substrate and verapamil is a P-gp inhibitor. Increased concentrations of edoxaban may occur during concomitant use of verapamil; monitor for increased adverse effects of edoxaban.
    Efavirenz: (Moderate) Use caution and careful monitoring when coadministering efavirenz with calcium-channel blockers; efavirenz induces CYP3A4, potentially altering serum concentrations of drugs metabolized by this enzyme such as some calcium-channel blockers. When coadministered, efavirenz decreases the concentrations of diltiazem (decrease in Cmax by 60%, in AUC by 69%, and in Cmin by 63%) and its active metabolites, desacetyl diltiazem and N-monodesmethyl diltiazem; dose adjustments should be made for diltiazem based on clinical response. No data are available regarding coadministration of efavirenz with other calcium channel blockers that are CYP3A4 substrates (e.g., felodipine, nicardipine, and verapamil); as with diltiazem, calcium-channel blocker doses should be adjusted based on clinical response.
    Efavirenz; Emtricitabine; Tenofovir: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as verapamil. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions. (Moderate) Use caution and careful monitoring when coadministering efavirenz with calcium-channel blockers; efavirenz induces CYP3A4, potentially altering serum concentrations of drugs metabolized by this enzyme such as some calcium-channel blockers. When coadministered, efavirenz decreases the concentrations of diltiazem (decrease in Cmax by 60%, in AUC by 69%, and in Cmin by 63%) and its active metabolites, desacetyl diltiazem and N-monodesmethyl diltiazem; dose adjustments should be made for diltiazem based on clinical response. No data are available regarding coadministration of efavirenz with other calcium channel blockers that are CYP3A4 substrates (e.g., felodipine, nicardipine, and verapamil); as with diltiazem, calcium-channel blocker doses should be adjusted based on clinical response.
    Elbasvir; Grazoprevir: (Moderate) Administering elbasvir; grazoprevir with verapamil may cause the plasma concentrations of all three drugs to increase; thereby increasing the potential for adverse effects (i.e., elevated ALT concentrations and hepatotoxicity). Verapamil is a substrate and moderate inhibitor of CYP3A. Both elbasvir and grazoprevir are metabolized by CYP3A, and grazoprevir is also a weak CYP3A inhibitor. If these drugs are used together, closely monitor for signs of hepatotoxicity.
    Eliglustat: (Major) In intermediate or poor CYP2D6 metabolizers (IMs or PM), coadministration of verapamil (including trandolapril; verapamil) and eliglustat is not recommended. In extensive CYP2D6 metabolizers (EMs), coadministration of these agents requires dosage reduction of eliglustat to 84 mg PO once daily. The coadministration of eliglustat with both verapamil and a moderate or strong CYP2D6 inhibitor is contraindicated in all patients. Verapamil is a moderate CYP3A inhibitor and P-glycoprotein (P-gp) substrate; eliglustat is a CYP3A and CYP2D6 substrate and P-gp inhibitor. Coadministration of eliglustat with CYP3A inhibitors, such as verapamil, may increase eliglustat exposure and the risk of serious adverse events (e.g., QT prolongation and cardiac arrhythmias); this risk is the highest in CYP2D6 IMs and PMs because a larger portion of the eliglustat dose is metabolized via CYP3A. In addition, coadministration of eliglustat with P-gp substrates (e.g., verapamil) may result in increased concentrations of the concomitant drug; monitor patients closely for adverse events, and consider reducing the dosage of verapamil and titrating to clinical effect.
    Empagliflozin: (Moderate) Administer antidiabetic agents with caution in patients receiving calcium-channel blockers. These drugs may cause hyperglycemia leading to a temporary loss of glycemic control in patients receiving antidiabetic agents. Close observation and monitoring of blood glucose is necessary to maintain adequate glycemic control. (Moderate) Angiotensin-converting enzyme inhibitors (ACE inhibitors) may enhance the hypoglycemic effects antidiabetic agents, such as empagliflozin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control.
    Empagliflozin; Linagliptin: (Moderate) ACE inhibitors may enhance the hypoglycemic effects antidiabetic agents, such as linagliptin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control. In addition, coadministration may increase the risk for angioedema. (Moderate) Administer antidiabetic agents with caution in patients receiving calcium-channel blockers. These drugs may cause hyperglycemia leading to a temporary loss of glycemic control in patients receiving antidiabetic agents. Close observation and monitoring of blood glucose is necessary to maintain adequate glycemic control. (Moderate) Angiotensin-converting enzyme inhibitors (ACE inhibitors) may enhance the hypoglycemic effects antidiabetic agents, such as empagliflozin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control.
    Empagliflozin; Metformin: (Moderate) Administer antidiabetic agents with caution in patients receiving calcium-channel blockers. These drugs may cause hyperglycemia leading to a temporary loss of glycemic control in patients receiving antidiabetic agents. Close observation and monitoring of blood glucose is necessary to maintain adequate glycemic control. (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control. (Moderate) Angiotensin-converting enzyme inhibitors (ACE inhibitors) may enhance the hypoglycemic effects antidiabetic agents, such as empagliflozin, by improving insulin sensitivity. Patients receiving these drugs concomitantly with antidiabetic agents should be monitored for changes in glycemic control.
    Emtricitabine; Rilpivirine; Tenofovir alafenamide: (Moderate) Close clinical monitoring is advised when administering verapamil with rilpivirine due to an increased potential for rilpivirine-related adverse events. Although this interaction has not been studied, predictions can be made based on metabolic pathways. Verapamil is an inhibitor of the hepatic isoenzyme CYP3A4; rilpivirine is metabolized by this isoenzyme. Coadministration may result in increased rilpivirine plasma concentrations. (Moderate) Coadministration of verapamil and tenofovir alafenamide may result in elevated tenofovir concentrations. Verapamil is an inhibitor of the drug transporter P-glycoprotein (P-gp). Tenofovir alafenamide is a substrate for P-gp. Of note, when tenofovir alafenamide is administered as part of a cobicistat-containing product, its availability is increased by cobicistat and a further increase of tenofovir alafenamide concentrations is not expected upon coadministration of an additional P-gp inhibitor.
    Emtricitabine; Rilpivirine; Tenofovir disoproxil fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as verapamil. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions. (Moderate) Close clinical monitoring is advised when administering verapamil with rilpivirine due to an increased potential for rilpivirine-related adverse events. Although this interaction has not been studied, predictions can be made based on metabolic pathways. Verapamil is an inhibitor of the hepatic isoenzyme CYP3A4; rilpivirine is metabolized by this isoenzyme. Coadministration may result in increased rilpivirine plasma concentrations.
    Emtricitabine; Tenofovir alafenamide: (Moderate) Coadministration of verapamil and tenofovir alafenamide may result in elevated tenofovir concentrations. Verapamil is an inhibitor of the drug transporter P-glycoprotein (P-gp). Tenofovir alafenamide is a substrate for P-gp. Of note, when tenofovir alafenamide is administered as part of a cobicistat-containing product, its availability is increased by cobicistat and a further increase of tenofovir alafenamide concentrations is not expected upon coadministration of an additional P-gp inhibitor.
    Emtricitabine; Tenofovir disoproxil fumarate: (Moderate) Caution is advised when administering tenofovir, PMPA, a P-glycoprotein (P-gp) substrate, concurrently with inhibitors of P-gp, such as verapamil. Coadministration may result in increased absorption of tenofovir. Monitor for tenofovir-associated adverse reactions.
    Enflurane: (Major) The depression of cardiac contractility, conductivity, and automaticity as well as the vascular dilation associated with general anesthetics may be potentiated by calcium-channel blockers. Alternatively, general anesthetics can potentiate the hypotensive effects of calcium-channel blockers. When used concomitantly, anesthetics and calcium-channel blockers should be titrated carefully to avoid excessive cardiovascular depression. (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Entecavir: (Moderate) Because entecavir is primarily eliminated by the kidneys and ACE inhibitors can affect renal function, concurrent administration with ACE inhibitors may increase the serum concentrations of entecavir and adverse events. Monitor for adverse effects when these drugs are coadministered.
    Enzalutamide: (Moderate) Monitor blood pressure and heart rate if coadministration of verapamil with enzalutamide is necessary. Concomitant use may decrease plasma concentrations of verapamil. Verapamil is a CYP3A4 substrate and enzalutamide is a strong CYP3A4 inducer.
    Ephedrine: (Major) The cardiovascular effects of sympathomimetics, such as ephedrine, may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Blood pressure and heart rates should be monitored closely to confirm that the desired antihypertensive effect is achieved. (Major) The cardiovascular effects of sympathomimetics, such as ephedrine, may reduce the antihypertensive effects produced by calcium-channel blockers. Blood pressure and heart rates should be monitored closely to confirm that the desired antihypertensive effect is achieved.
    Epirubicin: (Major) Close cardiac monitoring is recommended throughout therapy in patients receiving concomitant treatment with epirubicin and calcium-channel blockers. Individuals receiving these medications concurrently are at increased risk of developing heart failure.
    Eplerenone: (Major) Eplerenone is metabolized by the CYP3A4 pathway. Coadministration of eplerenone with verapamil has resulted in 2- to 2.9-fold increases in eplerenone AUC. Increased eplerenone concentrations may lead to a risk of developing hyperkalemia and hypotension. If these medications are given concurrently in post-myocardial infarction patients with heart failure, do not exceed an eplerenone dose of 25 mg PO once daily. If these medications are given concurrently, and eplerenone is used for hypertension, initiate eplerenone at 25 mg PO once daily. The dose may be increased to a maximum of 25 mg PO twice daily for inadequate blood pressure response. (Major) Monitor serum potassium and serum creatinine concentrations within 3 to 7 days of initiating coadministration of eplerenone and angiotensin-converting enzyme (ACE) inhibitors. Hyperkalemia risk is increased when eplerenone is used with ACE inhibitors. Patients who develop hyperkalemia may continue eplerenone with proper dose adjustment; eplerenone dose reduction decreases potassium concentrations.
    Epoprostenol: (Moderate) Calcium-channel blockers can have additive hypotensive effects with other antihypertensive agents. This additive effect can be desirable, but the patient should be monitored carefully and the dosage should be adjusted based on clinical response.
    Eprosartan: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Eprosartan; Hydrochlorothiazide, HCTZ: (Major) Most patients receiving the combination of two renin-angiotensin-aldosterone system (RAAS) inhibitors, such as angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin II receptor antagonists (ARBs) do not obtain any additional benefit compared to monotherapy. In general, avoid combined use of these drugs together. Closely monitor blood pressure, renal function, and electrolytes. Combination therapy has been associated with an increased risk of diarrhea, hypotension, syncope, hyperkalemia, and renal dysfunction resulting in dialysis, doubling of serum creatinine, and death. In the Ongoing Telmisartan Alone and in Combination with Ramipril Global Endpoint Trial (ONTARGET), the combination of ramipril 10 mg/day and telmisartan 80 mg/day did not provide a significant benefit in the prevention of death from cardiovascular causes, myocardial infarction, stroke, or hospitalization for heart failure compared to ramipril alone. There was, however, a significantly increased rate of renal dysfunction associated with combination therapy (13.5%) compared to ramipril (10.2%) or telmisartan (10.6%) alone and a significantly increased rate of hyperkalemia with combination therapy compared to ramipril (5.6% vs. 3.3%; p<0.001). Additionally, there was a significantly higher number of patients who discontinued therapy due to adverse reactions, including hypotensive symptoms (4.8% vs. 1.7%; p<0.001), syncope (0.3% vs. 0.2%; p=0.03), diarrhea (0.5% vs. 0.1%; p<0.001), and renal impairment (1.1% vs. 0.7%; p<0.001), from combination therapy compared to ramipril alone. In a separate analysis of the ONTARGET renal outcomes, the rate of the composite primary renal outcome of dialysis, doubling of serum creatinine, and death was similar with ramipril and telmisartan alone (13.5% vs. 13.6%, respectively), but was significantly higher with combination therapy (14.5%) compared to ramipril (p=0.037). In the CHARM-Added program, the combination of candesartan and an ACE-inhibitor resulted in an increased incidence of hypotension (22.6% vs. 13.8%), renal dysfunction (15% vs. 9%), and hyperkalemia (9.5% vs. 3.5%) compared to placebo combined with an ACE inhibitor. In the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) trial, no additional benefit over monotherapy was seen in patients receiving the combination of losartan and lisinopril compared to monotherapy; however, there was an increased incidence of hyperkalemia and acute renal injury. Patients receiving concomitant therapy with ACE inhibitors and ARBs should be closely monitored for renal dysfunction, hypotension, and hyperkalemia.
    Ergoloid Mesylates: (Major) Verapamil is an inhibitor of CYP3A4 isoenzymes. Co-administration with verapamil may lead to an increase in serum levels of drugs that are CYP3A4 substrates, such as ergoloid mesylates.
    Ergonovine: (Major) Because of its potential to cause coronary vasospasm, ergonovine could theoretically antagonize the therapeutic effects of anti-anginal agents including calcium-channel blockers. In addition, calcium-channel blockers with CYP3A4 inhibitory properties, such as diltiazem, nicardipine, and verapamil, may also reduce the hepatic metabolism of ergonovine and increase the risk of ergot toxicity.
    Ergotamine: (Major) Because of the potential to cause coronary vasospasm , ergotamine theoretically could antagonize the therapeutic effects of calcium-channel blockers. Clinicians should also note that calcium-channel blockers with CYP3A4 inhibitory properties, such as diltiazem, nicardipine, and verapamil, may also reduce the hepatic metabolism of ergotamine and increase the risk of ergot toxicity.
    Erlotinib: (Major) Avoid the coadministration of erlotinib with verapamil due to the risk of increased erlotinib-related adverse reactions; if concomitant use is unavoidable and severe reactions occur, reduce the dose of erlotinib by 50 mg decrements. Erlotinib is primarily metabolized by CYP3A4, and to a lesser extent by CYP1A2. Verapamil is a moderate CYP3A4 inhibitor and a weak inhibitor of 1A2. Coadministration of erlotinib with ketoconazole, a strong CYP3A4 inhibitor, increased the erlotinib AUC by 67%. Coadministration of erlotinib with ciprofloxacin, a moderate inhibitor of CYP3A4 and CYP1A2, increased the erlotinib AUC by 39% and the Cmax by 17%; coadministration with verapamil may also increase erlotinib exposure.
    Erythromycin: (Major) Avoid administration of erythromycin and a calcium-channel blocker, particularly in geriatric patients. Coadministration has been associated with an increased risk of hypotension and shock. Azithromycin may be preferred if the use of a macrolide antibiotic is necessary in a patient receiving calcium-channel blocker therapy. Erythromycin may also decrease the clearance of calcium-channel blockers (e.g., diltiazem, felodipine, and verapamil) via inhibition of CYP3A4 metabolism. Concurrent use of erythromycin with diltiazem and verapamil has been associated with sudden cardiac death. This interaction is likely due to the combined inhibition of CYP3A by erythromycin and the calcium channel blockers leading to increases in the serum concentrations of erythromycin and the calcium channel blockers.
    Erythromycin; Sulfisoxazole: (Major) Avoid administration of erythromycin and a calcium-channel blocker, particularly in geriatric patients. Coadministration has been associated with an increased risk of hypotension and shock. Azithromycin may be preferred if the use of a macrolide antibiotic is necessary in a patient receiving calcium-channel blocker therapy. Erythromycin may also decrease the clearance of calcium-channel blockers (e.g., diltiazem, felodipine, and verapamil) via inhibition of CYP3A4 metabolism. Concurrent use of erythromycin with diltiazem and verapamil has been associated with sudden cardiac death. This interaction is likely due to the combined inhibition of CYP3A by erythromycin and the calcium channel blockers leading to increases in the serum concentrations of erythromycin and the calcium channel blockers.
    Esmolol: (Moderate) Oral calcium-channel blockers and beta-blockers like esmolol are used together for their therapeutic benefits to reduce angina and improve exercise tolerance. However, concomitant administration of beta-adrenergic blocking agents and verapamil can lead to significant AV nodal blockade. This can manifest as heart block, bradycardia, cardiac conduction abnormalities and/or prolonged PR interval. Congestive heart failure or severe hypotension also can occur. The combination of beta-blockers and verapamil should be avoided in patients with poor ventricular function due to increased negative inotropic effects.
    Esomeprazole; Naproxen: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Estazolam: (Moderate) Verapamil is a CYP3A4 inhibitor and may reduce the metabolism of estazolam and increase the potential for benzodiazepine toxicity.
    Esterified Estrogens: (Minor) Estrogens are partially metabolized by CYP3A4. Drugs that inhibit CYP3A4 such as verapamil may increase plasma concentrations of estrogens and cause estrogen-related side effects such as nausea and breast tenderness. Patients receiving estrogens should be monitored for an increase in adverse events.
    Esterified Estrogens; Methyltestosterone: (Minor) Estrogens are partially metabolized by CYP3A4. Drugs that inhibit CYP3A4 such as verapamil may increase plasma concentrations of estrogens and cause estrogen-related side effects such as nausea and breast tenderness. Patients receiving estrogens should be monitored for an increase in adverse events.
    Estradiol Cypionate; Medroxyprogesterone: (Minor) Estrogens can induce fluid retention and may increase blood pressure in some patients; patients who are receiving antihypertensive agents concurrently with hormonal contraceptives should be monitored for antihypertensive effectiveness. (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Estradiol: (Minor) Estrogens can induce fluid retention and may increase blood pressure in some patients; patients who are receiving antihypertensive agents concurrently with hormonal contraceptives should be monitored for antihypertensive effectiveness. (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Estradiol; Levonorgestrel: (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Estradiol; Norethindrone: (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Estradiol; Norgestimate: (Minor) Verapamil inhibits CYP3A4 activity. Serum estrogen concentrations and estrogenic-related side effects (e.g., nausea, breast tenderness) may potentially increase when verapamil is coadministered with either estrogens or combined hormonal contraceptives.
    Estropipate: (Minor) Estrogens are partially metabolized by CYP3A4. Drugs that inhibit CYP3A4 such as verapamil may increase plasma concentrations of estrogens and cause estrogen-related side effects such as nausea and breast tenderness. Patients receiving estrogens should be monitored for an increase in adverse events.
    Eszopiclone: (Moderate) Patients should be advised of the potential for next-day psychomotor and/or memory impairment during coadministration of eszopiclone and CYP3A4 inhibitors, such as verapamil. CYP3A4 is a primary metabolic pathway for eszopiclone, and increased systemic exposure to eszopiclone increases the risk of next-day impairment, which may decrease the ability to perform tasks requiring full mental alertness such as driving.
    Ethanol: (Major) Verapamil has been found to significantly inhibit ethanol elimination resulting in elevated blood ethanol concentrations that may prolong the intoxicating effects of alcohol. The patient may experience an increase in sedation, dizziness, hypotension, and CNS depression. Advise the patient to limit alcohol ingestion during verapamil therapy.
    Ethinyl Estradiol: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Desogestrel: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Ethynodiol Diacetate: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Etonogestrel: (Minor) Coadministration of etonogestrel and moderate CYP3A4 inhibitors such as verapamil may increase the serum concentration of etonogestrel. (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Levonorgestrel: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Levonorgestrel; Folic Acid; Levomefolate: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norelgestromin: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norethindrone Acetate: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norethindrone Acetate; Ferrous fumarate: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norethindrone: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norethindrone; Ferrous fumarate: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norgestimate: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethinyl Estradiol; Norgestrel: (Minor) Estrogen containing oral contraceptives can induce fluid retention and may increase blood pressure in some patients.
    Ethosuximide: (Moderate) Verapamil is an inhibitor of CYP3A4 isoenzymes. Co-administration with verapamil may lead to an increase in serum levels of drugs that are CYP3A4 substrates including ethosuximide.
    Etodolac: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Etomidate: (Major) The depression of cardiac contractility, conductivity, and automaticity as well as the vascular dilation associated with general anesthetics may be potentiated by calcium-channel blockers. Alternatively, general anesthetics can potentiate the hypotensive effects of calcium-channel blockers. When used concomitantly, anesthetics and calcium-channel blockers should be titrated carefully to avoid excessive cardiovascular depression. (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Etonogestrel: (Minor) Coadministration of etonogestrel and moderate CYP3A4 inhibitors such as verapamil may increase the serum concentration of etonogestrel.
    Etoposide, VP-16: (Major) Monitor for an increased incidence of etoposide-related adverse effects if used concomitantly with verapamil. Verapamil is an inhibitor of CYP3A4 and P-glycoprotein (P-gp); etoposide, VP-16 is a CYP3A4 and P-gp substrate. Coadministration may cause accumulation of etoposide and decreased metabolism, resulting in increased etoposide concentrations.
    Etravirine: (Moderate) Etravirine is a CYP3A4 inducer/substrate, a CYP2C9 inhibitor/substrate, a CYP2C19 inhibitor/substrate, and a P-glycoprotein (P-gp) inhibitor. Verapamil is a CYP3A4 substrate/inhibitor, a CYP2C9 substrate, a CYP2C19 substrate, and P-gp substrate/inhibitor. Caution is warranted if these drugs are coadministered.
    Everolimus: (Major) A dose adjustment of everolimus is necessary when prescribed with verapamil due to increased plasma concentrations of everolimus. For patients with breast cancer, neuroendocrine tumors, renal cell carcinoma, and renal angiolipoma with tubular sclerosis complex (TSC), reduce the dose of Afinitor to 2.5 mg once daily; consider increasing the dose to 5 mg based on patient tolerance. For patients with subependymal giant cell astrocytoma (SEGA) with TSC, the recommended starting dose of Afinitor/Afinitor Disperz is 2.5 mg/m2 once daily, rounded to the nearest tablet strength; subsequent dosing should be guided by therapeutic drug monitoring (TDM), with administration every other day if dose reduction is required for patients receiving the lowest available tablet strength. If verapamil is discontinued, increase everolimus to its original dose after a washout period of 2 to 3 days. Zortress dosing for prophylaxis of organ rejection should be guided by TDM. Everolimus is a CYP3A4 substrate as well as a substrate of P-glycoprotein (P-gp); verapamil is a moderate CYP3A4 and P-gp inhibitor. Coadministration with verapamil increased everolimus exposure by 3.5-fold. (Moderate) The risk of angioedema, with or without respiratory impairment, may be increased if everolimus is given with other drugs known to cause angioedema such as the angiotensin-converting enzyme inhibitors (ACE inhibitors). In a pooled analysis of randomized, double-blind oncology clinical trials, angioedema was reported in 6.8% of patients receiving concomitant everolimus and ACE inhibitor therapy, compared to 1.3% of patients with an ACE inhibitor alone. If coadministration is necessary, educate patients regarding signs and symptoms of angioedema and monitor therapy closely.
    Ezetimibe; Simvastatin: (Major) Do not exceed a simvastatin dose of 10 mg/day in patients taking verapamil due to increased risk of myopathy, including rhabdomyolysis. For patients chronically receiving simvastatin 80 mg/day who need to be started on verapamil, consider switching to an alternative statin with less potential for interaction. Carefully weigh the benefits of combined use of verapamil and simvastatin against the potential risks. Verapamil increases the simvastatin exposure by approximately 2-fold. The interaction is presumed due to increased simvastatin bioavailability via inhibition of CYP3A4 metabolism and reduction of first-pass metabolism by verapamil.
    Famotidine; Ibuprofen: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Fenoprofen: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Fentanyl: (Major) Verapamil is an inhibitor of CYP3A4 isoenzymes. Co-administration with verapamil may lead to an increase in serum levels of drugs that are CYP3A4 substrates, such as fentanyl. Also, the risk of significant hypotension and/or bradycardia during therapy with fentanyl is increased in patients receiving calcium-channel blockers.
    Fesoterodine: (Moderate) Fesoterodine is rapidly hydrolyzed to its active metabolite, 5-hydroxymethyltolterodine, which is metabolized via hepatic CYP3A4. In theory, the CYP3A4 inhibitory effects of verapamil may result in an increase in plasma concentrations of 5-hydroxymethyltolterodine. The need for fesoterodine doses greater than 4 mg/day should be carefully evaluated prior to increasing the dose during concurrent use of mild to moderate 3A4 inhibitors.
    Fexofenadine; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Fingolimod: (Major) If possible, do not start fingolimod in a patient who is taking a drug that slows the heart rate or atrioventricular conduction such as verapamil. Use of these drugs during fingolimod initiation may be associated with severe bradycardia or heart block. Seek advice from the prescribing physician regarding the possibility to switch to drugs that do not slow the heart rate or atrioventricular conduction before initiating fingolimod. After the first fingolimod dose, overnight monitoring with continuous ECG in a medical facility is advised for patients who cannot stop taking drugs that slow the heart rate or atrioventricular conduction. Experience with fingolimod in patients receiving concurrent therapy with drugs that slow the heart rate or atrioventricular conduction is limited.
    Fish Oil, Omega-3 Fatty Acids (Dietary Supplements): (Moderate) Co-enzyme Q10, ubiquinone (CoQ10) may lower blood pressure. CoQ10 use in combination with antihypertensive agents may lead to additional reductions in blood pressure in some individuals. Patients who choose to take CoQ10 concurrently with antihypertensive medications should receive periodic blood pressure monitoring. Patients should be advised to inform their prescriber of their use of CoQ10. (Moderate) High doses of fish oil supplements may produce a blood pressure lowering effect. It is possible that additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents. (Moderate) High doses of fish oil supplements may produce a blood pressure lowering effect. It is possible that additive reductions in blood pressure may be seen when fish oils are used in a patient already taking antihypertensive agents.
    Flecainide: (Major) Concomitant therapy with flecainide and verapamil may result in additive negative inotropic effect and prolongation of atrioventricular conduction. A study in healthy volunteers has shown that the concomitant administration of flecainide and verapamil may have additive effects on myocardial contractility, AV conduction, and repolarization.
    Flibanserin: (Severe) The concomitant use of flibanserin and moderate CYP3A4 inhibitors, such as verapamil, is contraindicated. Moderate CYP3A4 inhibitors can increase flibanserin concentrations, which can cause severe hypotension and syncope. If initiating flibanserin following use of a moderate CYP3A4 inhibitor, start flibanserin at least 2 weeks after the last dose of the CYP3A4 inhibitor. If initiating a moderate CYP3A4 inhibitor following flibanserin use, start the moderate CYP3A4 inhibitor at least 2 days after the last dose of flibanserin.
    Fluconazole: (Moderate) Fluconazole may decrease the clearance of calcium-channel blockers, including verapamil, via inhibition of CYP3A4 metabolism.
    Fluorescein: (Moderate) Patients on angiotensin-converting enzyme inhibitors are at an increased risk of adverse reactions when administered fluorescein injection. If fluorescein injection is deemed necessary in a patient on ACE inhibitor therapy, monitor as appropriate during and after the procedure.
    Fluoxetine: (Moderate) Fluoxetine may decrease the clearance of calcium-channel blockers, including verapamil, via inhibition of CYP3A4 metabolism.
    Fluoxetine; Olanzapine: (Moderate) Fluoxetine may decrease the clearance of calcium-channel blockers, including verapamil, via inhibition of CYP3A4 metabolism. (Moderate) Olanzapine may induce orthostatic hypotension and thus enhance the effects of antihypertensive agents.
    Flurazepam: (Moderate) CYP3A4 inhibitors, such as verapamil, may reduce the metabolism of flurazepam and increase the potential for benzodiazepine toxicity.
    Flurbiprofen: (Moderate) If nonsteroidal anti-inflammatory drugs (NSAIDs) and an antihypertensive drug are concurrently used, carefully monitor the patient for signs and symptoms of renal insufficiency and blood pressure control. Doses of antihypertensive medications may require adjustment in patients receiving concurrent NSAIDs. NSAIDs, to varying degrees, have been associated with an elevation in blood pressure. This effect is most significant in patients receiving concurrent antihypertensive agents and long-term NSAID therapy. NSAIDs cause a dose-dependent reduction in prostaglandin formation, which may result in a reduction in renal blood flow leading to renal insufficiency and an increase in blood pressure that are often accompanied by peripheral edema and weight gain. Patients who rely upon renal prostaglandins to maintain renal perfusion may have acute renal blood flow reduction with NSAID usage. Elderly patients may be at increased risk of adverse effects from combined long-term NSAID therapy and antihypertensive agents, especially diuretics, due to age-related decreases in renal function and an increased risk of stroke and coronary artery disease.
    Fluticasone; Umeclidinium; Vilanterol: (Moderate) Umeclidinium is a P-gp substrate. When verapamil, a moderate P-gp transporter inhibitor, was given to healthy adult subjects at a dose of 240 mg once daily in combination with umeclidinium, no effect on umeclidinium Cmax was observed. However, an approximately 1.4-fold increase in umeclidinium AUC was observed.
    Fluvoxamine: (Moderate) Certain SSRIs, including fluvoxamine, are inhibitors of CYP3A4, and may theoretically increase verapamil serum concentrations.
    Food: (Moderate) The incidence of marijuana associated adverse effects may change following coadministration with verapamil. Verapamil is an inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of marijuana's most psychoactive compound, delta-9-tetrahydrocannabinol (Delta-9-THC). When given concurrently with verapamil, the amount of Delta-9-THC converted to the active metabolite 11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC) may be reduced. These changes in Delta-9-THC and 11-OH-THC plasma concentrations may result in an altered marijuana adverse event profile.
    Fosamprenavir: (Moderate) Coadministration of ritonavir with verapamil may increase the serum concentrations of verapamil, potentially resulting in verapamil toxicity. The manufacturer for ritonavir recommends caution when coadministering this combination. A similar effect could be expected with other anti-retroviral protease inhibitors, which are also inhibitors of CYP3A4.
    Fospropofol: (Major) The depression of cardiac contractility, conductivity, and automaticity as well as the vascular dilation associated with general anesthetics may be potentiated by calcium-channel blockers. Alternatively, general anesthetics can potentiate the hypotensive effects of calcium-channel blockers. When used concomitantly, anesthetics and calcium-channel blockers should be titrated carefully to avoid excessive cardiovascular depression. (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Gefitinib: (Major) Monitor for an increased incidence of gefitinib-related adverse effects if gefitinib and verapamil are used concomitantly; this also applies to trandolapril; verapamil. Gefitinib is metabolized significantly by CYP3A4 and verapamil is a moderate CYP3A4 inhibitor; coadministration may decrease the metabolism of gefitinib and increase gefitinib concentrations. While the manufacturer has provided no guidance regarding the use of gefitinib with mild or moderate CYP3A4 inhibitors, administration of a single 250 mg gefitinib dose with a strong CYP3A4 inhibitor (itraconazole) increased the mean AUC of gefitinib by 80%.
    General anesthetics: (Major) The depression of cardiac contractility, conductivity, and automaticity as well as the vascular dilation associated with general anesthetics may be potentiated by calcium-channel blockers. Alternatively, general anesthetics can potentiate the hypotensive effects of calcium-channel blockers. When used concomitantly, anesthetics and calcium-channel blockers should be titrated carefully to avoid excessive cardiovascular depression. (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Ginger, Zingiber officinale: (Minor) In vitro studies have demonstrated the positive inotropic effects of ginger, Zingiber officinale. It is theoretically possible that ginger could affect the action of antiarrhythmics, however, no clinical data are available.
    Ginkgo, Ginkgo biloba: (Moderate) Ginkgo biloba appears to inhibit the metabolism of calcium-channel blockers, perhaps by inhibiting the CYP3A4 isoenzyme. A non-controlled pharmacokinetic study in healthy volunteers found that the concurrent administration of ginkgo with nifedipine resulted in a 53% increase in nifedipine peak concentrations. More study is needed regarding ginkgo's effects on CYP3A4 and whether clinically significant drug interactions result.
    Ginseng, Panax ginseng: (Moderate) Ginseng appears to inhibit the metabolism of calcium-channel blockers, perhaps by inhibiting the CYP3A4 isoenzyme. A non-controlled pharmacokinetic study in healthy volunteers found that the concurrent administration of ginseng with nifedipine resulted in a 30% increase in nifedipine peak concentrations. More study is needed regarding ginseng's effects on CYP3A4 and whether clinically significant drug interactions result.
    Glecaprevir; Pibrentasvir: (Moderate) Caution is advised with the coadministration of glecaprevir and verapamil as coadministration may increase serum concentrations of both drugs and increase the risk of adverse effects. Glecaprevir and verapamil are both substrates and inhibitors of P-glycoprotein (P-gp). (Moderate) Caution is advised with the coadministration of pibrentasvir and verapamil as coadministration may increase serum concentrations of both drugs and increase the risk of adverse effects. Pibrentasvir and verapamil are both substrates and inhibitors of P-glycoprotein (P-gp).
    Glipizide; Metformin: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Glyburide; Metformin: (Moderate) Angiotensin-converting enzyme (ACE) inhibitors may enhance the hypoglycemic effects of insulin or other antidiabetic agents by improving insulin sensitivity. Patients receiving antidiabetic agents can become hypoglycemic if ACE inhibitors are administered concomitantly. ACE inhibitors may rarely reduce renal function, a risk factor for reduced renal clearance of metformin. Patients receiving these drugs together should be monitored for changes in renal function and glycemic control.
    Gold: (Minor) Nitritoid reactions (facial flushing, diaphoresis, dizziness, nausea/vomiting, hypotension, tachycardia, syncope, and anaphylactic type reactions) or vasomotor reactions have been reported rarely in patients receiving injectable gold and concomitant ACE inhibitor therapy. Monitor closely for nitritoid reactions during co-therapy with gold and ACE inhibitor agents.
    Grapefruit juice: (Major) Grapefruit juice contains an unknown compound that can inhibit the cytochrome P-450 CYP3A4 isozyme in the gut wall. Grapefruit juice can increase the serum concentrations and oral bioavailability of verapamil. Co-administration of oral verapamil with grapefruit juice significantly increases the AUC and peak plasma concentrations of verapamil. It is generally recommended to avoid grapefruit juice during verapamil therapy.
    Green Tea: (Minor) Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products such as green tea.
    Guaifenesin; Hydrocodone: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects.
    Guaifenesin; Hydrocodone; Pseudoephedrine: (Major) Monitor for respiratory depression and sedation if hydrocodone and verapamil are coadministered; consider dosage adjustments if necessary. Hydrocodone is metabolized by CYP3A4. Concomitant administration of a CYP3A4 inhibitor, such as verapamil, may cause an increase in hydrocodone plasma concentrations, which could increase or prolong adverse effects. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Guaifenesin; Phenylephrine: (Moderate) Phenylephrine's cardiovascular effects may reduce the antihypertensive effects of calcium-channel blockers. Well-controlled hypertensive patients receiving decongestant sympathomimetics at recommended doses do not appear to be at high risk for significant elevations in blood pressure; however, increased blood pressure (especially systolic hypertension) has been reported in some patients. (Moderate) The cardiovascular effects of sympathomimetics may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Well-controlled hypertensive patients receiving phenylephrine at recommended doses do not appear at high risk for significant elevations in blood pressure, however, increased blood pressure (especially systolic hypertension) has been reported in some patients.
    Guaifenesin; Pseudoephedrine: (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by angiotensin-converting enzyme inhibitors. Monitor heart rate and blood pressure. (Moderate) The cardiovascular effects of pseudoephedrine may reduce the antihypertensive effects produced by calcium-channel blockers. Monitor blood pressure and heart rate.
    Guanfacine: (Major) Verapamil may significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if these agents are taken together, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. Monitor patients closely for alpha-adrenergic effects including hypotension, drowsiness, lethargy, and bradycardia. Upon verapamil discontinuation, the guanfacine ER dosage should be increased back to the recommended dose. Guanfacine is primarily metabolized by CYP3A4, and verapamil is a moderate CYP3A4 inhibitor.
    Guarana: (Minor) Caffeine is an active component of guarana. Verapamil reduces the clearance of caffeine and increases serum caffeine concentrations, presumably via inhibition of hepatic metabolism. During concomitant therapy with verapamil, it may be prudent to advise patients to limit or minimize the intake of caffeinated products such as guarana and beverages including coffee, teas, or colas in an effort to minimize caffeine-related side effects.
    Halofantrine: (Moderate) Drugs which significantly inhibit cytochrome CYP3A4, such as verapamil, may lead to an inhibition of halofantrine metabolism, placing the patient at risk for halofantrine cardiac toxicity. If concurrent use of halofantrine and a CYP3A4 inhibitor is warranted, it would be prudent to use caution and monitor the ECG periodically.
    Haloperidol: (Moderate) In general, antipsychotics like haloperidol should be used cautiously with antihypertensive agents due to the possibility of additive hypotension. Verapamil is a substrate and inhibitor of CYP3A4. Mild to moderate increases in haloperidol plasma concentrations have been reported during concurrent use of haloperidol and substrates or inhibitors of CYP3A4 or CYP2D6. Elevated haloperidol concentrations occurring through inhibition of CYP2D6 or CYP3A4 may increase the risk of adverse effects, including QT prolongation. (Moderate) In general, haloperidol should be used cautiously with antihypertensive agents due to the possibility of additive hypotension.
    Halothane: (Major) The depression of cardiac contractility, conductivity, and automaticity as well as the vascular dilation associated with general anesthetics may be potentiated by calcium-channel blockers. Alternatively, general anesthetics can potentiate the hypotensive effects of calcium-channel blockers. When used concomitantly, anesthetics and calcium-channel blockers should be titrated carefully to avoid excessive cardiovascular depression. (Moderate) General anesthetics can potentiate the hypotensive effects of antihypertensive agents.
    Hawthorn,