CONTRAINDICATIONS / PRECAUTIONS
General Information
Sildenafil is contraindicated in patients with a known hypersensitivity to any component of the tablet or injection. The safety and efficacy of combinations of sildenafil with other treatments for erectile dysfunction have not been studied. Therefore, the use of such combinations is not recommended.
The use of sildenafil is not recommended in patients with pulmonary veno-occlusive disease (PVOD). Administration of sildenafil in this population may significantly worsen cardiovascular status. In addition, if signs of pulmonary edema occur during sildenafil administration, the possibility of associated PVOD should be considered.
Nitrate/nitrite therapy
Sildenafil is contraindicated in patients taking nitrate/nitrite therapy. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of organic nitrates and nitrites. Patients receiving nitrates in any form are not to receive sildenafil. This includes any patient who receives intermittent nitrate therapies. It is unknown if it is safe for patients to receive nitrates once sildenafil has been administered.
Geriatric, hepatic disease, renal impairment
The following factors are associated with an increase in sildenafil exposure when the drug is used for erectile dysfunction compared with healthy subjects: geriatric adults over 65 years of age, hepatic disease (e.g., cirrhosis), and those with severe renal impairment (i.e., CrCl less than 30 mL/minute); a reduced sildenafil initial dosage is recommended in those with these conditions taking the drug for erectile dysfunction. Concurrent use of moderate to potent CYP3A4 inhibitors increases sildenafil exposure and dosage adjustments may be necessary and recommendations may vary depending on the indication for use.
Angina, aortic stenosis, cardiac arrhythmias, cardiac disease, coronary artery disease, heart failure, hypertension, hypotension, idiopathic hypertrophic subaortic stenosis, myocardial infarction, stroke
There is a degree of cardiac risk associated with sexual activity; therefore, prescribers should evaluate the cardiovascular status of their patients prior to initiating any treatment for erectile dysfunction. Over 75 deaths due to cardiovascular events have been reported in association with sildenafil use. In a study conducted at the Mayo Clinic, sildenafil was shown to have limited cardiovascular effects during exercise in men with known or probable coronary artery disease. The study reported that sildenafil had no effect on exercise capacity or the hemodynamic response to exercise. Systolic blood pressure was reduced an average of 7 mmHg compared to baseline. Another study showed that sildenafil inhibited beta-adrenergic-stimulated systolic function. Using dobutamine in healthy volunteers, investigators reported that sildenafil suppressed the cardiac response to dobutamine but had minimal effect under resting conditions. It was also reported that the effects of sildenafil were independent of cardiac afterload or preload changes. Health care professionals should consider whether the individual would be adversely affected by vasodilatory events. In particular, caution should be used if sildenafil is prescribed in the following patient groups: patients who have suffered a myocardial infarction, stroke, or life-threatening cardiac arrhythmias in the last 6 months; patients with resting hypotension (BP less than 90/50 mmHg) or resting hypertension (BP greater than 170/100 mmHg); patients with fluid depletion; patients with cardiac disease, heart failure or coronary artery disease which causes unstable angina. The American College of Cardiology recommends that sildenafil be used with caution in the following: patients with active coronary ischemia who are not taking nitrates (e.g., positive exercise test for ischemia); patients with congestive heart failure and borderline low blood pressure and borderline low volume status; patients on a complicated, multidrug, antihypertensive program; and patients taking drugs that can prolong the half-life of sildenafil. However, one study reported that sildenafil was effective and well tolerated in patients on multidrug antihypertensive regimens and was not associated with additional safety risks in these patients. Patients with left ventricular outflow obstruction (e.g., aortic stenosis, idiopathic hypertrophic subaortic stenosis) and those with severely impaired autonomic control of blood pressure can be particularly sensitive to the actions of sildenafil and other vasodilators. Doses of sildenafil above 25 mg should not be given within 4 hours of an alpha-blocker.
Leukemia, multiple myeloma, penile structural abnormality, Peyronie's disease, polycythemia, priapism
Prolonged erections greater than 4 hours and priapism (painful erections greater than 6 hours in duration) have been associated with PDE5 inhibitor administration. Priapism, if not treated promptly, can result in irreversible damage to the erectile tissue. Patients who have an erection lasting greater than 4 hours, whether painful or not, should seek emergency medical attention. Sildenafil and other agents for the treatment of erectile dysfunction should be used with caution in patients with penile structural abnormality (such as angulation, cavernosal fibrosis or Peyronie's disease), or in patients who have conditions which may predispose them to priapism (such as sickle cell anemia, leukemia, multiple myeloma, polycythemia, or a history of priapism). However, in one retrospective study, treatment with sildenafil did not cause any worsening deformity or progression of Peyronie's disease.
Human immunodeficiency virus (HIV) infection
Patients should be reminded that sildenafil, when used for erectile dysfunction, offers no protection against sexually transmitted disease. Counseling of patients about protective measures, including the prevention of transmission of human immunodeficiency virus (HIV) infection, should be considered.
Coagulopathy, peptic ulcer disease
Sildenafil has no effect on bleeding time when taken alone or with aspirin. In vitro studies with human platelets indicate that sildenafil potentiates the antiaggregatory effect of sodium nitroprusside (a nitric oxide donor). There is no safety information on the administration of sildenafil to patients with a coagulopathy or active peptic ulcer disease. Therefore, sildenafil should be administered with caution to these patients.
Non-arteritic anterior ischemic optic neuropathy, retinitis pigmentosa, visual disturbance
Use sildenafil cautiously in patients with pre-existing visual disturbance. Advise patients to seek immediate medical attention in the event of a sudden loss of vision in 1 or both eyes while taking sildenafil. Postmarketing reports of sudden vision loss have occurred with phosphodiesterase inhibitors. Vision loss is attributed to a condition known as non-arteritic anterior ischemic optic neuropathy (NAION). Most reports of NAION associated with sildenafil have had underlying anatomic or vascular risk factors, including low cup to disc ratio ('crowded disc'). There is no safety or efficacy information on the administration of sildenafil to patients with retinitis pigmentosa. A minority of patients with the inherited condition have genetic disorders of retinal phosphodiesterases; therefore, use of sildenafil in patients with retinitis pigmentosa is not recommended.
Pregnancy
Limited data do not report a clear association with the use of sildenafil and major birth defects, miscarriage, or adverse maternal or fetal outcomes when sildenafil is used during pregnancy. No evidence of teratogenicity or embryofetal toxicity was observed in animal reproduction studies using sildenafil at doses 32- and 65-times the recommended human dose. There are risks to the mother and fetus from untreated pulmonary arterial hypertension.
Breast-feeding
Limited clinical data preclude a clear determination of the risk of sildenafil to an infant during breast-feeding. Data from a case report describe the presence of sildenafil and its active metabolite in human milk. There is insufficient information on the effects of sildenafil on the breast-fed infant and no information on the effects of sildenafil on milk production.
Neonates, premature neonates
Delay sildenafil use in extremely premature neonates until retinal vascularization is established. Phosphodiesterase type 5 (PDE5) inhibitors cross the blood-retina barrier and can inhibit retina-specific phosphodiesterase type 6 (PDE6). Expression of PDE6 in rod and cone photoreceptors of retinal tissue, and the discovery of PDE5 on retinal and choroid vasculature have raised concerns about the potential adverse effects sildenafil may have on the developing eye of premature neonates. An increased risk in the development or severity of retinopathy of prematurity has not been observed in retrospective studies ; however, further study is warranted.
Gastroesophageal reflux disease (GERD), hiatal hernia
Sildenafil should be used cautiously in patients with gastroesophageal reflux disease (GERD) or hiatal hernia associated with reflux esophagitis. Sildenafil can decrease the tone of the lower esophageal sphincter and inhibit esophageal motility.
Sickle cell disease
Safety and efficacy of sildenafil has not been established in the treatment of pulmonary hypertension secondary to sickle cell disease. Vaso-occlusive crisis (sickle-cell crisis) requiring hospitalization has been reported more frequently in patients with pulmonary hypertension secondary to sickle cell disease who received sildenafil than by those who received placebo. Also, when using for erectile dysfunction, use sildenafil with caution in patients with sickle cell disease because the risk of priapism may be increased.
DRUG INTERACTIONS
Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Acetaminophen; Chlorpheniramine; Phenylephrine : (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Acetaminophen; Dextromethorphan; Guaifenesin; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Acetaminophen; Dextromethorphan; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Acetaminophen; Guaifenesin; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Adagrasib: (Major) Coadministration with adagrasib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving adagrasib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Adagrasib is a strong CYP3A inhibitor and sildenafil is a sensitive CYP3A substrate. Coadministration of other strong CYP3A inhibitors increased the sildenafil AUC between 3- and 11-fold.
Alfuzosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alfuzosin therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of alfuzosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and alfuzosin.
Aliskiren: (Moderate) Aliskiren can enhance the effects of sildenafil on blood pressure if given concomitantly. This additive effect may be desirable, but dosages must be adjusted accordingly. Blood pressure and electrolytes should be routinely monitored in patients receiving aliskiren.
Aliskiren; Hydrochlorothiazide, HCTZ: (Moderate) Aliskiren can enhance the effects of sildenafil on blood pressure if given concomitantly. This additive effect may be desirable, but dosages must be adjusted accordingly. Blood pressure and electrolytes should be routinely monitored in patients receiving aliskiren.
Alpha-blockers: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of the alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and an alpha-blocker.
Ambrisentan: (Moderate) Although no specific interactions have been documented, ambrisentan has vasodilatory effects and may contribute additive hypotensive effects when given with other antihypertensive agents. Patients receiving ambrisentan in combination with other antihypertensive agents should be monitored for decreases in blood pressure.
Amiodarone: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with amiodarone is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and amiodarone is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Amlodipine: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amlodipine; Atorvastatin: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amlodipine; Benazepril: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amlodipine; Celecoxib: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amlodipine; Olmesartan: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amlodipine; Valsartan: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amlodipine; Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Amoxicillin; Clarithromycin; Omeprazole: (Major) Coadministration of clarithromycin is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving clarithromycin. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Clarithromycin is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Amyl Nitrite: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Consistent with their known effects on the nitric oxide/cGMP pathway, concomitant use of phosphodiesterase inhibitors and nitrates can cause severe hypotension, syncope, or myocardial infarction. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.
Apalutamide: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with apalutamide is necessary. Sildenafil is a sensitive CYP3A4 substrate and apalutamide is a strong CYP3A4 inducer. Concomitant administration of strong CYP3A inducers is expected to substantially decrease plasma concentrations of sildenafil. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Aprepitant, Fosaprepitant: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministered with multi-day regimens of oral aprepitant. A dose reduction of sildenafil may be required when using for erectile dysfunction. Sildenafil is a CYP3A4 substrate and aprepitant, when administered as a 3-day oral regimen (125 mg/80 mg/80 mg), is a moderate CYP3A4 inhibitor. When administered as a single oral or single intravenous dose, the inhibitory effect of aprepitant on CYP3A4 is weak and did not result in a clinically significant increase in the AUC of a sensitive substrate.
Atazanavir: (Major) Sildenafil is contraindicated for use with atazanavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; atazanavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Atazanavir; Cobicistat: (Major) Sildenafil is contraindicated for use with atazanavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; atazanavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold. (Major) Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; cobicistat is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Atropine; Difenoxin: (Moderate) Diphenoxylate/difenoxin is a synthetic opiate agonist with a chemical structure similar to that of meperidine. Prolonged erections have been reported in two patients taking sildenafil with dihydrocodeine. In both cases, patients reported erections subsided immediately after orgasm when taking sildenafil alone. Although more data are needed, use caution when prescribing opiate agonists and sildenafil concomitantly.
Barbiturates: (Minor) Sildenafil is metabolized principally by the hepatic CYP3A4 and CYP2C9 isoenzymes. It can be expected that concomitant administration of CYP3A4 enzyme-inducers will decrease plasma levels of sildenafil, however, no interaction studies have been performed. CYP3A4 inducers include barbiturates.
Belzutifan: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with belzutifan is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and belzutifan is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Berotralstat: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with berotralstat is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and berotralstat is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Brigatinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with brigatinib is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and brigatinib is a weak CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Brompheniramine; Dextromethorphan; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Brompheniramine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Carbamazepine: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with carbamazepine is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and carbamazepine is a strong CYP3A inducer. Concomitant administration of strong CYP3A inducers is expected to substantially decrease plasma concentrations of sildenafil.
Carbinoxamine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Cariprazine: (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.
Cenobamate: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with cenobamate is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and cenobamate is a moderate CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Ceritinib: (Major) Coadministration with ceritinib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving ceritinib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ceritinib is a strong CYP3A4 inhibitor and sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Chloramphenicol: (Major) Coadministration of chloramphenicol is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving chloramphenicol. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Chloramphenicol is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Chlorpheniramine; Dextromethorphan; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Chlorpheniramine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Cimetidine: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with cimetidine is necessary. Concomitant use may increase sildenafil plasma concentrations. Cimetidine 800 mg caused a 56% increase in plasma sildenafil concentrations when coadministered with sildenafil 50 mg to healthy volunteers. Sildenafil is a CYP2C9 and CYP3A substrate and cimetidine is a nonspecific CYP inhibitor.
Ciprofloxacin: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with ciprofloxacin is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and ciprofloxacin is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Clarithromycin: (Major) Coadministration of clarithromycin is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving clarithromycin. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Clarithromycin is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Cobicistat: (Major) Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; cobicistat is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Codeine; Phenylephrine; Promethazine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Conivaptan: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with conivaptan is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A substrate and conivaptan is a moderate CYP3A inhibitor. In a drug interaction study, coadministration with a moderate CYP3A inhibitor increased the peak and overall exposure of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Crizotinib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with crizotinib is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and crizotinib is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Dabrafenib: (Major) The concomitant use of dabrafenib and sildenafil may lead to decreased sildenafil concentrations and loss of efficacy. Use of an alternative agent is recommended. If concomitant use of these agents together is unavoidable, monitor patients for loss of sildenafil efficacy. Dabrafenib is a moderate CYP3A4 inducer and sildenafil is a sensitive CYP3A4 substrate. Concomitant use of dabrafenib with a single dose of another sensitive CYP3A4 substrate decreased the AUC value of the sensitive CYP3A4 substrate by 65%.
Danazol: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with danazol is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and danazol is a CYP3A4 inhibitor.
Darunavir: (Major) Sildenafil is contraindicated for use with darunavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; darunavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Darunavir; Cobicistat: (Major) Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; cobicistat is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold. (Major) Sildenafil is contraindicated for use with darunavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; darunavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Major) Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; cobicistat is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold. (Major) Sildenafil is contraindicated for use with darunavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; darunavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Dasabuvir; Ombitasvir; Paritaprevir; Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use substantially increases the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ritonavir, a strong CYP3A4 inhibitor, increased the AUC of sildenafil, a sensitive CYP3A4 substrate, by 11-fold in a drug interaction study.
Delavirdine: (Major) Coadministration of delavirdine is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Delavirdine is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Dexamethasone: (Minor) Sildenafil is metabolized principally by CYP3A4. It can be expected that concomitant administration of sildenafil with CYP3A4 enzyme inducers like dexamethasone will decrease plasma concentrations of sildenafil.
Dextromethorphan; Diphenhydramine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Dextromethorphan; Guaifenesin; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Dextromethorphan; Quinidine: (Moderate) Sildenafil is metabolized principally by the hepatic isoenzymes CYP3A4 and CYP2C9. Inhibitors of these isoenzymes, such as quinidine, may reduce sildenafil clearance. Increased systemic exposure to sildenafil may result in an increase in sildenafil-induced adverse effects.
Diltiazem: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with diltiazem is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and diltiazem is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Diphenhydramine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Diphenoxylate; Atropine: (Moderate) Diphenoxylate/difenoxin is a synthetic opiate agonist with a chemical structure similar to that of meperidine. Prolonged erections have been reported in two patients taking sildenafil with dihydrocodeine. In both cases, patients reported erections subsided immediately after orgasm when taking sildenafil alone. Although more data are needed, use caution when prescribing opiate agonists and sildenafil concomitantly.
Doxazosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of the alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and an alpha-blocker.
Dronedarone: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with dronedarone is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and dronedarone is a moderate CYP3A4 inhibitor.
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. It is advisable to monitor blood pressure if the combination is necessary.
Dutasteride; Tamsulosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and tamsulosin.
Duvelisib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with duvelisib is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A substrate; duvelisib is a moderate CYP3A inhibitor.
Efavirenz: (Moderate) Efavirenz induces CYP3A4 and may decrease serum concentrations of drugs metabolized by this enzyme, such as sildenafil.
Efavirenz; Emtricitabine; Tenofovir Disoproxil Fumarate: (Moderate) Efavirenz induces CYP3A4 and may decrease serum concentrations of drugs metabolized by this enzyme, such as sildenafil.
Efavirenz; Lamivudine; Tenofovir Disoproxil Fumarate: (Moderate) Efavirenz induces CYP3A4 and may decrease serum concentrations of drugs metabolized by this enzyme, such as sildenafil.
Elagolix: (Moderate) Monitor for reduced therapeutic effect of sildenafil if coadministered with elagolix. Concurrent use may decrease sildenafil plasma concentrations. Sildenafil is a sensitive CYP3A4 substrate; elagolix is a weak to moderate CYP3A4 inducer. Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was coadministered with weak CYP3A inducers.
Elagolix; Estradiol; Norethindrone acetate: (Moderate) Monitor for reduced therapeutic effect of sildenafil if coadministered with elagolix. Concurrent use may decrease sildenafil plasma concentrations. Sildenafil is a sensitive CYP3A4 substrate; elagolix is a weak to moderate CYP3A4 inducer. Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was coadministered with weak CYP3A inducers.
Elbasvir; Grazoprevir: (Moderate) Administering sildenafil with elbasvir; grazoprevir may result in elevated sildenafil plasma concentrations. Sildenafil is a substrate of CYP3A; grazoprevir is a weak CYP3A inhibitor. If these drugs are used together, closely monitor for signs of adverse events.
Elexacaftor; tezacaftor; ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; sildenafil is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as sildenafil, can theoretically increase sildenafil exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Alafenamide: (Major) Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; cobicistat is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; cobicistat is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Encorafenib: (Moderate) Coadministration of encorafenib with sildenafil may result in increased toxicity or decreased efficacy of sildenafil. Sildenafil is a sensitive CYP3A4 substrate. In vitro studies with encorafenib showed time-dependent inhibition of CYP3A4 and induction of CYP3A4. The clinical relevance of the in vivo effect of encorafenib on CYP3A4 is not established.
Enzalutamide: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with enzalutamide is necessary. Sildenafil is a CYP3A4 (major) and CYP2C9 (minor) substrate. Enzalutamide is a strong CYP3A4 inducer and a moderate inducer of CYP2C9. Concomitant administration of strong CYP3A inducers is expected to substantially decrease plasma concentrations of sildenafil. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Erythromycin: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with erythromycin is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and erythromycin is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with erythromycin increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Etravirine: (Moderate) Etravirine is an inducer of CYP3A4; coadministration may result in decreased sildenafil concentrations. Dosage adjustments may be needed based on clinical efficacy.
Fedratinib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with fedratinib is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and fedratinib is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Fenofibric Acid: (Minor) At therapeutic concentrations, fenofibric acid is a mild-to-moderate inhibitor of CYP2C9. Concomitant use of fenofibric acid with CYP2C9 substrates, such as sildenafil , has not been formally studied. Fenofibric acid may theoretically increase plasma concentrations of CYP2C9 substrates and could lead to toxicity for drugs that have a narrow therapeutic range. Monitor the therapeutic effect of sildenafil during coadministration with fenofibric acid.
Fluconazole: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with fluconazole is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and fluconazole is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Fluvoxamine: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with fluvoxamine is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and fluvoxamine is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration of fluvoxamine increased the sildenafil AUC by 40%.
Fosamprenavir: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with fosamprenavir is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. When used for pulmonary arterial hypertension, this combination is listed as a contraindication in the fosamprenavir FDA-approved labeling. Sildenafil is a sensitive CYP3A substrate and fosamprenavir is a moderate CYP3A inhibitor. In a drug interaction study, coadministration with a moderate CYP3A inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Grapefruit juice: (Moderate) Sildenafil is metabolized via the cytochrome CYP 3A4 isozyme. Grapefruit juice contains a compound that inhibits CYP3A4 in enterocytes in the GI tract. Sildenafil levels may increase; it is possible that sildenafil-induced side effects could also be increased in some individuals. One study has confirmed a potential interaction; sildenafil's AUC increased 23 percent with coadministration of grapefruit juice.
Guaifenesin; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Hydantoins: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with phenytoin is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and phenytoin is a strong CYP3A inducer. Concomitant administration of strong CYP3A inducers is expected to substantially decrease plasma concentrations of sildenafil.
Hydralazine; Isosorbide Dinitrate, ISDN: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Consistent with their known effects on the nitric oxide/cGMP pathway, concomitant use of phosphodiesterase inhibitors and nitrates can cause severe hypotension, syncope, or myocardial infarction. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.
Idelalisib: (Major) Coadministration of idelalisib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving idelalisib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Idelalisib is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Imatinib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with imatinib is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and imatinib is a moderate CYP3A4 inhibitor.
Indinavir: (Major) Sildenafil is contraindicated for use with indinavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; indinavir is a strong CYP3A4 inhibitor. In a small pharmacokinetic study, the coadministration of a single dose of sildenafil (25 mg) to patients receiving indinavir (800 mg every 8 hours) resulted in markedly increased sildenafil AUC values (340% increase), as compared to historical controls. In two of the six subjects, prolonged clinical effects of sildenafil were noted for 72 hours after a single dose of sildenafil.
Isavuconazonium: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with isavuconazonium is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and isavuconazonium is a moderate CYP3A4 inhibitor.
Isocarboxazid: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with sildenafil. Careful monitoring of blood pressure is suggested during concurrent therapy of MAOIs with sildenafil.
Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Minor) Sildenafil is metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. It can be expected that concomitant administration of CYP3A4 enzyme-inducers, such as rifampin, will decrease plasma levels of sildenafil, however, no interaction studies have been performed.
Isoniazid, INH; Rifampin: (Minor) Sildenafil is metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. It can be expected that concomitant administration of CYP3A4 enzyme-inducers, such as rifampin, will decrease plasma levels of sildenafil, however, no interaction studies have been performed.
Isosorbide Dinitrate, ISDN: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Consistent with their known effects on the nitric oxide/cGMP pathway, concomitant use of phosphodiesterase inhibitors and nitrates can cause severe hypotension, syncope, or myocardial infarction. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.
Isosorbide Mononitrate: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Consistent with their known effects on the nitric oxide/cGMP pathway, concomitant use of phosphodiesterase inhibitors and nitrates can cause severe hypotension, syncope, or myocardial infarction. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.
Itraconazole: (Major) Avoid use of sildenafil for the treatment of pulmonary hypertension during and for 2 weeks after discontinuation of itraconazole treatment. When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving itraconazole. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Itraconazole is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; sildenafil is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as sildenafil, can theoretically increase sildenafil exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Ivosidenib: (Moderate) Monitor for loss of efficacy of sildenafil during coadministration of ivosidenib; a sildenafil dose adjustment may be necessary. Sildenafil is a sensitive substrate of CYP3A4; ivosidenib induces CYP3A4 and may lead to decreased sildenafil concentrations.
Ketoconazole: (Major) Coadministration of ketoconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving ketoconazole. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ketoconazole is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Lansoprazole; Amoxicillin; Clarithromycin: (Major) Coadministration of clarithromycin is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving clarithromycin. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Clarithromycin is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Lefamulin: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with oral lefamulin is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and oral lefamulin is a moderate CYP3A4 inhibitor; an interaction is not expected with intravenous lefamulin. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Lenacapavir: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with lenacapavir is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A substrate and lenacapavir is a moderate CYP3A inhibitor. In a drug interaction study, coadministration with a moderate CYP3A inhibitor increased the AUC of sildenafil by 182%. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Lesinurad: (Moderate) Lesinurad may decrease the systemic exposure and therapeutic efficacy of sildenafil; monitor for potential reduction in efficacy. Sildenafil is a CYP3A substrate, and lesinurad is a weak CYP3A inducer.
Lesinurad; Allopurinol: (Moderate) Lesinurad may decrease the systemic exposure and therapeutic efficacy of sildenafil; monitor for potential reduction in efficacy. Sildenafil is a CYP3A substrate, and lesinurad is a weak CYP3A inducer.
Letermovir: (Major) Monitor for an increase in sildenafil-related adverse reactions if coadministration with letermovir is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Concurrent use is not recommended in patients receiving sildenafil for pulmonary arterial hypertension and taking cyclosporine, because the magnitude of the interaction may be amplified. Consider a starting dose of 25 mg of sildenafil for erectile dysfunction in patients receiving letermovir with cyclosporine. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is metabolized principally by CYP3A4. Letermovir is a moderate CYP3A4 inhibitor; however, when given with cyclosporine, the combined effect on CYP3A4 substrates is similar to a strong CYP3A4 inhibitor.
Levamlodipine: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Levoketoconazole: (Major) Coadministration of ketoconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving ketoconazole. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ketoconazole is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Lonafarnib: (Major) Coadministration with lonafarnib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving lonafarnib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate and lonafarnib is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Lopinavir; Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use substantially increases the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ritonavir, a strong CYP3A4 inhibitor, increased the AUC of sildenafil, a sensitive CYP3A4 substrate, by 11-fold in a drug interaction study.
Lorcaserin: (Moderate) Lorcaserin is a serotonin 2C receptor agonist, and priapism is a potential effect of 5-HT2C receptor agonism. Because there is little experience with the combination of lorcaserin and medications indicated for erectile dysfunction (e.g., phosphodiesterase inhibitors), combined use should be approached with caution.
Lorlatinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with lorlatinib is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and lorlatinib is a moderate CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Lumacaftor; Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; sildenafil is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as sildenafil, can theoretically increase sildenafil exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Lurasidone: (Moderate) Due to the antagonism of lurasidone at alpha-1 adrenergic receptors, the drug may enhance the hypotensive effects of antihypertensive agents. If concurrent use of lurasidone 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.
Mavacamten: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with mavacamten is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and mavacamten is a moderate CYP3A inducer.
Mifepristone: (Major) Coadministration with mifepristone is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving mifepristone. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A substrate and mifepristone is a strong CYP3A inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Mitapivat: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with mitapivat is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and mitapivat is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Mitotane: (Major) Use caution if mitotane and sildenafil are used concomitantly, and monitor for decreased efficacy of sildenafil and a possible change in dosage requirements. Mitotane is a strong CYP3A4 inducer and sildenafil is a CYP3A4 substrate; coadministration may result in decreased plasma concentrations of sildenafil. Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was co-administered with mild CYP3A inducers.
Mobocertinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with mobocertinib is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and mobocertinib is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Monoamine oxidase inhibitors: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with sildenafil. Careful monitoring of blood pressure is suggested during concurrent therapy of MAOIs with sildenafil.
Nebivolol: (Moderate) Monitor closely for decreased efficacy of either drug if sildenafil is coadministered with nebivolol. The AUC of sildenafil was decreased by 21% when coadministered with nebivolol. A similar decrease in the concentration of d-nebivolol (less than 20% in the AUC) was also observed with coadministration of sildenafil.
Nebivolol; Valsartan: (Moderate) Monitor closely for decreased efficacy of either drug if sildenafil is coadministered with nebivolol. The AUC of sildenafil was decreased by 21% when coadministered with nebivolol. A similar decrease in the concentration of d-nebivolol (less than 20% in the AUC) was also observed with coadministration of sildenafil.
Nefazodone: (Major) Coadministration of nefazodone is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving nefazodone. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Nefazodone is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Nelfinavir: (Major) Sildenafil is contraindicated for use with nelfinavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; nelfinavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Nesiritide, BNP: (Major) No formal drug interaction trials have been conducted with nesiritide. Sildenafil use within 24 hours was an exclusion criteria for nesiritide treatment during clinical trials. Although not identified during clinical trials, the potential for symptomatic hypotension may be significantly increased when coadministering nesiritide with sildenafil. Sildenafil should be avoided within 24 hours before or after nesiritide use.
Netupitant, Fosnetupitant; Palonosetron: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with netupitant; palonosetron is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and netupitant is a moderate CYP3A4 inhibitor.
Nevirapine: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with nevirapine is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and nevirapine is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Nicardipine: (Moderate) Nicardipine is an inhibitor of CYP3A4 isoenzymes. Co-administration with nicardipine may lead to an increase in serum levels of drugs that are CYP3A4 substrates, such as sildenafil.
Nifedipine: (Moderate) Nifedipine can have additive hypotensive effects when administered with phosphodiesterase inhibitors (PDE 5 inhibitors). The patient should be monitored carefully and the dosage should be adjusted based on clinical response. For example, in patients whose hypertension was controlled with nifedipine, vardenafil produced mean additional supine systolic/diastolic blood pressure reductions of 3 to 4 mmHg (age group 65 to 69 years) and 5 to 6 mmHg (age group 70 to 80 years) compared to placebo.
Nilotinib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with nilotinib is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and nilotinib is a moderate CYP3A4 inhibitor.
Nirmatrelvir; Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use substantially increases the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ritonavir, a strong CYP3A4 inhibitor, increased the AUC of sildenafil, a sensitive CYP3A4 substrate, by 11-fold in a drug interaction study. (Major) Concomitant use of ritonavir-boosted nirmatrelvir and sildenafil, when used for pulmonary arterial hypertension (PAH), is contraindicated; consider an alternative COVID-19 therapy. Consider withholding sildenafil, when used for erectile dysfunction, during concomitant receipt of ritonavir-boosted nirmatrelvir. Coadministration may increase sildenafil exposure resulting in increased toxicity. sildenafil is a CYP3A substrate and nirmatrelvir is a CYP3A inhibitor.
Nitrates: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Consistent with their known effects on the nitric oxide/cGMP pathway, concomitant use of phosphodiesterase inhibitors and nitrates can cause severe hypotension, syncope, or myocardial infarction. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.
Nitroglycerin: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Consistent with their known effects on the nitric oxide/cGMP pathway, concomitant use of phosphodiesterase inhibitors and nitrates can cause severe hypotension, syncope, or myocardial infarction. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.
Nitroprusside: (Contraindicated) Concomitant use of nitroprusside and sildenafil is contraindicated due to the risk of additive hypotension. If the patient has taken sildenafil, at least 24 hours must elapse before nitroprusside administration is considered; monitor hemodynamics closely. In addition, sildenafil may potentiate the nitric oxide-mediated platelet anti-aggregatory effect of nitroprusside.
Odevixibat: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with odevixibat is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and odevixibat is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Olmesartan; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Olutasidenib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with olutasidenib is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and olutasidenib is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Omaveloxolone: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with omaveloxolone is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and omaveloxolone is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Ombitasvir; Paritaprevir; Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use substantially increases the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ritonavir, a strong CYP3A4 inhibitor, increased the AUC of sildenafil, a sensitive CYP3A4 substrate, by 11-fold in a drug interaction study.
Omeprazole; Amoxicillin; Rifabutin: (Minor) Sildenafil is metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. It can be expected that concomitant administration of CYP3A4 enzyme-inducers, such as rifabutin, will decrease plasma levels of sildenafil, however, no interaction studies have been performed.
Oritavancin: (Moderate) Coadministration of oritavancin and sildenafil may result in increases or decreases in sildenafil exposure and may increase side effects or decrease efficacy of sildenafil. Sildenafil is primarily metabolized by CYP3A4, but is also metabolized by CYP2C9. Oritavancin weakly induces CYP3A4, while weakly inhibiting CYP2C9. If these drugs are administered concurrently, monitor the patient for signs of toxicity or lack of efficacy.
Pazopanib: (Moderate) Pazopanib is a weak inhibitor of CYP3A4. Coadministration of pazopanib and sildenafil, a CYP3A4 substrate, may cause an increase in systemic concentrations of sildenafil. Use caution when administering these drugs concomitantly.
Perindopril; Amlodipine: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Pexidartinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with pexidartinib is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and pexidartinib is a moderate CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Phenelzine: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with sildenafil. Careful monitoring of blood pressure is suggested during concurrent therapy of MAOIs with sildenafil.
Phenoxybenzamine: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of the alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and an alpha-blocker.
Phentolamine: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of the alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and an alpha-blocker.
Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Posaconazole: (Major) Coadministration of posaconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving posaconazole. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Posaconazole is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Prazosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of the alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and an alpha-blocker.
Promethazine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. A decreased pressor effect of phenylephrine might occur. Monitor for proper blood pressure when these drugs are used together.
Quinidine: (Moderate) Sildenafil is metabolized principally by the hepatic isoenzymes CYP3A4 and CYP2C9. Inhibitors of these isoenzymes, such as quinidine, may reduce sildenafil clearance. Increased systemic exposure to sildenafil may result in an increase in sildenafil-induced adverse effects.
Quinine: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with quinine is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and quinine is a moderate CYP3A4 inhibitor.
Ranolazine: (Moderate) Sildenafil is metabolized principally by the hepatic CYP3A4 (major route) and 2C9 (minor route) isoenzymes. Inhibitors of these isoenzymes may reduce sildenafil clearance. Increased systemic exposure to sildenafil may result in an increase in sildenafil-induced adverse effects. The manufacturer recommends dosage reduction in patients receiving potent cytochrome CYP3A4 inhibitors. Population data from patients in clinical trials did indicate a reduction in sildenafil clearance when it was coadministered with CYP3A4 inhibitors. CYP3A4 inhibitors include ranolazine.
Rasagiline: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with antihypertensives or medications with hypotensive properties. Careful monitoring of blood pressure is suggested during concurrent therapy of MAOIs with vasodilators. Patients should be instructed to rise slowly from a sitting position, and to report syncope or changes in blood pressure or heart rate to their health care provider.
Ribociclib: (Major) Coadministration with ribociclib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving ribociclib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ribociclib is a strong CYP3A4 inhibitor and sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Ribociclib; Letrozole: (Major) Coadministration with ribociclib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving ribociclib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ribociclib is a strong CYP3A4 inhibitor and sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Rifabutin: (Minor) Sildenafil is metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. It can be expected that concomitant administration of CYP3A4 enzyme-inducers, such as rifabutin, will decrease plasma levels of sildenafil, however, no interaction studies have been performed.
Rifampin: (Minor) Sildenafil is metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. It can be expected that concomitant administration of CYP3A4 enzyme-inducers, such as rifampin, will decrease plasma levels of sildenafil, however, no interaction studies have been performed.
Rifapentine: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with rifapentine is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and rifapentine is a strong CYP3A4 inducer. Concomitant administration of strong CYP3A4 inducers is expected to substantially decrease plasma concentrations of sildenafil. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Riociguat: (Contraindicated) Use of riociguat and sildenafil is contraindicated due to the risk of hypotension. Discontinue riociguat at least 24 hours prior to sildenafil administration and do not administer within 24 hours of sildenafil. Monitor for signs and symptoms of hypotension during transition of therapy. PDE5 inhibitors, including sildenafil, may potentiate the hypotensive effects of riociguat.
Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use substantially increases the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Ritonavir, a strong CYP3A4 inhibitor, increased the AUC of sildenafil, a sensitive CYP3A4 substrate, by 11-fold in a drug interaction study.
Sapropterin: (Moderate) Sapropterin acts as a cofactor in the synthesis of nitric oxide and may cause vasorelaxation. Caution should be exercised when administering sapropterin in combination with drugs that affect nitric oxide-mediated vasorelaxation such as phosphodiesterase inhibitors. When given together these agents may produce an additive reduction in blood pressure. The combination of sapropterin and a phosphodiesterase (PDE5) inhibitor did not significantly reduce blood pressure when administered concomitantly in animal studies. The additive effect of these agents has not been studied in humans.
Saquinavir: (Major) Sildenafil is contraindicated for use with saquinavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; saquinavir is a strong CYP3A4 inhibitor. Coadministration of saquinavir increased the sildenafil AUC by about 3-fold in a drug interaction study.
Silodosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on silodosin therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of silodosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and silodosin.
Simeprevir: (Moderate) Coadministration of sildenafil with simeprevir, an intestinal CYP3A4 inhibitor, may result in mild increases in sildenafil plasma concentrations. No dose adjustments are required when treating erectile dysfunction. If treating pulmonary arterial hypertension, start at the lowest sildenafil dose and increase as needed while monitoring clinically.
Sodium Phenylbutyrate; Taurursodiol: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with taurursodiol is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and taurursodiol is a weak CYP3A inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A inducers.
Sotorasib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with sotorasib is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and sotorasib is a moderate CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
St. John's Wort, Hypericum perforatum: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with St. John's Wort is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A substrate and St. John's Wort is a strong CYP3A inducer. Concomitant administration of strong CYP3A inducers is expected to substantially decrease plasma concentrations of sildenafil.
Stiripentol: (Moderate) Consider a dose adjustment of sildenafil when coadministered with stiripentol. Coadministration may alter plasma concentrations of sildenafil resulting in an increased risk of adverse reactions and/or decreased efficacy. Sildenafil is a sensitive CYP3A4 substrate. In vitro data predicts inhibition or induction of CYP3A4 by stiripentol potentially resulting in clinically significant interactions.
Tacrolimus: (Moderate) Consider initiating sildenafil at a low dose (25 mg) in kidney transplant recipients receiving tacrolimus. In a study of renal transplant patients, coadministration of tacrolimus with a single 50 mg dose of sildenafil resulted in an increase in the AUC, Cmax, and half-life of sildenafil. Decreases in blood pressure were also observed. No significant effect on the pharmacokinetic parameters of tacrolimus were observed.
Tamsulosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and tamsulosin.
Tazemetostat: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with tazemetostat is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and tazemetostat is a weak CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Telmisartan; Amlodipine: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure (SBP) was 8 mmHg systolic and 7 mmHg diastolic.
Telotristat Ethyl: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with telotristat is necessary as concurrent use may decrease sildenafil exposure. Sildenafil is a sensitive CYP3A4 substrate and telotristat is a weak CYP3A4 inducer. Population pharmacokinetic analysis indicates an approximately 3-fold increase in sildenafil clearance with concomitant use of weak CYP3A4 inducers.
Terazosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of the alpha-blocker; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and an alpha-blocker.
Tezacaftor; Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Ivacaftor is an inhibitor of CYP3A and a weak inhibitor of CYP2C9; sildenafil is metabolized by CYP3A and CYP2C9. Co-administration of ivacaftor with CYP3A and CYP2C9 substrates, such as sildenafil, can theoretically increase sildenafil exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Tipranavir: (Major) Sildenafil is contraindicated for use with tipranavir when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg in 48 hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is a sensitive CYP3A4 substrate; tipranavir is a strong CYP3A4 inhibitor. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Trandolapril; Verapamil: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with verapamil is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Tranylcypromine: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with sildenafil. Careful monitoring of blood pressure is suggested during concurrent therapy of MAOIs with sildenafil.
Tucatinib: (Major) Coadministration with tucatinib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving tucatinib. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Tucatinib is a strong CYP3A4 inhibitor and sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Vemurafenib: (Moderate) Concomitant use of vemurafenib with sildenafil may increase sildenafil exposure. In vitro studies suggest vemurafenib inhibits CYP3A and CYP2C9. Sildenafil is cleared predominantly by CYP3A (major route) and CYP2C9 (minor route). Use caution and monitor patients for potential sildenafil-related side effects.
Verapamil: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with verapamil is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and verapamil is a moderate CYP3A4 inhibitor. In a drug interaction study, coadministration with a moderate CYP3A4 inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A4 inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Vericiguat: (Contraindicated) Use of vericiguat and sildenafil is contraindicated due to the risk of hypotension. Monitor for signs and symptoms of hypotension during transition of therapy. PDE5 inhibitors, including sildenafil, may potentiate the hypotensive effects of vericiguat.
Vigabatrin: (Major) Vigabatrin should not be used with phosphodiesterase inhibitors, which is associated with serious ophthalmic effects (e.g., retinopathy or glaucoma) unless the benefit of treatment clearly outweighs the risks.
Vonoprazan; Amoxicillin; Clarithromycin: (Major) Coadministration of clarithromycin is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving clarithromycin. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Clarithromycin is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Voriconazole: (Major) Coadministration of voriconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving voriconazole. Concurrent use may increase sildenafil plasma concentrations resulting in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Voriconazole is a strong CYP3A4 inhibitor; sildenafil is a sensitive CYP3A4 substrate. Coadministration of other strong CYP3A4 inhibitors increased the sildenafil AUC between 3- and 11-fold.
Voxelotor: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with voxelotor is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A substrate and voxelotor is a moderate CYP3A inhibitor. In a drug interaction study, coadministration with a moderate CYP3A inhibitor increased the Cmax and AUC of sildenafil by 160% and 182%, respectively. Predictions based on a pharmacokinetic model suggest that drug-drug interactions with CYP3A inhibitors will be less for sildenafil injection than those observed after oral sildenafil administration.
Zafirlukast: (Moderate) Concomitant use of zafirlukast with sildenafil may increase sildenafil exposure. In vitro studies suggest zafirlukast inhibits CYP3A (weak) and CYP2C9 (moderate top potent). Sildenafil is cleared predominantly by CYP3A (major route) and CYP2C9 (minor route). Use caution and monitor patients for potential sildenafil-related side effects.