Proloprim

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Proloprim

Classes

Trimethoprim and Derivative Antibiotics

Administration
Oral Administration

If gastric irritation occurs, administer with food.

Adverse Reactions
Severe

aseptic meningitis / Delayed / 0-1.0
megaloblastic anemia / Delayed / Incidence not known
methemoglobinemia / Early / Incidence not known
toxic epidermal necrolysis / Delayed / Incidence not known
Stevens-Johnson syndrome / Delayed / Incidence not known
exfoliative dermatitis / Delayed / Incidence not known
acute generalized exanthematous pustulosis (AGEP) / Delayed / Incidence not known
hyperkalemia / Delayed / Incidence not known
azotemia / Delayed / Incidence not known
C. difficile-associated diarrhea / Delayed / Incidence not known

Moderate

cholestasis / Delayed / 0-1.0
jaundice / Delayed / 0-1.0
glossitis / Early / Incidence not known
neutropenia / Delayed / Incidence not known
thrombocytopenia / Delayed / Incidence not known
leukopenia / Delayed / Incidence not known
pseudomembranous colitis / Delayed / Incidence not known
superinfection / Delayed / Incidence not known
candidiasis / Delayed / Incidence not known
hyperbilirubinemia / Delayed / Incidence not known
elevated hepatic enzymes / Delayed / Incidence not known
hyponatremia / Delayed / Incidence not known

Mild

rash / Early / 1.3-6.7
pruritus / Rapid / 2.9-6.7
maculopapular rash / Early / 2.9-6.7
diarrhea / Early / 4.2-4.2
vomiting / Early / 1.6-1.6
abdominal pain / Early / 0-1.0
nausea / Early / Incidence not known
photosensitivity / Delayed / Incidence not known
fever / Early / Incidence not known

Common Brand Names

Primsol, Proloprim, TRIMPEX

Dea Class

Rx

Description

Synthetic antifolate-type antiinfective agent. Has activity against gram-positive and gram-negative bacteria. Commonly used for UTI, prophylaxis of UTI, traveler's diarrhea, and in combination with sulfamethoxazole or dapsone for prophylaxis and treatment of Pneumocystis infections.

Dosage And Indications
For the treatment of acute otitis media due to susceptible strains of S. pneumoniae or H. influenzae.
NOTE: Moraxella catarrhalis isolates were found consistently resistant to trimethoprim in vitro. Therefore, when infection with M. catarrhalis is suspected, the use of alternative agents is recommended.
Oral dosage (Only Primsol FDA-approved) Infants >= 6 months, Children, and Adolescents

5 mg/kg PO every 12 hours (total dose 10 mg/kg/day) for 10 days. Maximum dosage is 400 mg/day. Trimethoprim has been shown to be clinically equivalent to sulfamethoxazole-trimethoprim (SMX-TMP) in the treatment of acute otitis media, with a clinical success rate of 90% at 5 days post treatment. NOTE: Primsol is not indicated for prophylactic or prolonged treatment of otitis media.

For the treatment of urinary tract infection (UTI), including cystitis and pyelonephritis. For the treatment of unspecified uncomplicated UTI. Oral dosage Adults

100 mg PO every 12 hours or 200 mg PO every 24 hours for 10 days. 

For the treatment of acute uncomplicated cystitis in nonpregnant persons. Oral dosage Adults

200 mg PO every 12 hours for 3 to 5 days.

For the treatment of lower UTI with prostate involvement†. Oral dosage Adults

200 mg PO every 12 hours for 7 days.

Adolescents 16 to 17 years

200 mg PO every 12 hours for 7 days.

For the treatment of acute uncomplicated pyelonephritis in nonpregnant persons. Oral dosage Adults

200 mg PO every 12 hours for 14 days.

Adolescents 16 to 17 years

200 mg PO every 12 hours for 14 days.

For the treatment of acute uncomplicated lower UTI in pediatric patients. Oral dosage Adolescents 16 to 17 years

200 mg PO every 12 hours for 3 days in nonpregnant persons.

Children and Adolescents 12 to 15 years

200 mg PO every 12 hours for 3 days.

Children 6 to 11 years

4 mg/kg/dose (Max: 200 mg/dose) PO every 12 hours or 100 mg PO every 12 hours for 3 days.

Infants and Children 6 months to 5 years

4 mg/kg/dose PO every 12 hours or 50 mg PO every 12 hours for 3 days.

Infants 3 to 5 months

4 mg/kg/dose PO every 12 hours or 25 mg PO every 12 hours for 3 days.

For urinary tract infection (UTI) prophylaxis† for recurrent infections. Oral dosage Adults

100 mg PO every 24 hours. The duration of prophylaxis is variable and should be assessed routinely. Generally 3 to 12 months is suggested; however, longer durations have been used.

For the treatment of Pneumocystis pneumonia (PCP)†. For the treatment of PCP in HIV-infected patients†. Oral dosage Adults

5 mg/kg/dose PO 3 times daily in combination with dapsone for 21 days as alternative therapy for mild to moderate infection then chronic suppressive therapy.

Infants, Children, and Adolescents

5 mg/kg/dose PO 3 times daily in combination with dapsone for 21 days as alternative therapy for mild to moderate infection then chronic suppressive therapy.

For the treatment of PCP in patients with hematological malignancies, cancer, or autoimmune/inflammatory disease† or solid organ transplant recipients†. Oral dosage Adults

5 mg/kg/dose PO 3 times daily in combination with dapsone for 14 to 21 days as alternative therapy for mild to moderate infection. 

Infants, Children, and Adolescents

5 mg/kg/dose PO 3 times daily in combination with dapsone for 14 to 21 days as alternative therapy for mild to moderate infection. 

For the treatment of acute exacerbations of bronchiectasis†. Oral dosage Adults

200 mg PO every 12 hours for 14 days in combination with rifampin.

Children and Adolescents 12 to 17 years

200 mg PO every 12 hours for 14 days in combination with rifampin.

Infants and children 1 month to 11 years

4 mg/kg/dose (Max: 200 mg/dose) PO every 12 hours for 14 days in combination with rifampin.

†Indicates off-label use

Dosing Considerations
Hepatic Impairment

Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.

Renal Impairment

CrCl > 30 ml/min: no dosage adjustment needed.
CrCl 15—30 ml/min: reduce recommended dose by 50%.
CrCl < 15 ml/min: use is not recommended.
 
Intermittent hemodialysis
Supplemental dosing is required following completion of hemodialysis.

Drug Interactions

Abacavir; Lamivudine, 3TC; Zidovudine, ZDV: (Moderate) Concomitant use of trimethoprim and zidovudine may result in additive hematological abnormalities. Use caution and monitor for hematologic toxicity during concurrent use.
Amantadine: (Major) Avoid concurrent use of amantadine and trimethoprim. A single case of toxic delirium has been reported after coadministration of trimethoprim and amantadine. Amantadine is an OCT2 substrate and trimethoprim is an OCT2 inhibitor.
Amiloride: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Amiloride; Hydrochlorothiazide, HCTZ: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Amitriptyline: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Amlodipine; Benazepril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Amlodipine; Olmesartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Amlodipine; Valsartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Amlodipine; Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Angiotensin II receptor antagonists: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Angiotensin-converting enzyme inhibitors: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Atovaquone: (Moderate) Concomitant administration of atovaquone with an oral combination of trimethoprim and sulfamethoxazole lead to a minor decreases in TMP and SMX AUCs by 16% and 10%, respectively, in a small number of HIV-positive subjects. No difference was observed in atovaquone pharmacokinetics. The effect of the interaction of atovaquone with TMP-SMX is minor and unlikely to be of clinical significance.
Atovaquone; Proguanil: (Moderate) Concomitant administration of atovaquone with an oral combination of trimethoprim and sulfamethoxazole lead to a minor decreases in TMP and SMX AUCs by 16% and 10%, respectively, in a small number of HIV-positive subjects. No difference was observed in atovaquone pharmacokinetics. The effect of the interaction of atovaquone with TMP-SMX is minor and unlikely to be of clinical significance.
Azathioprine: (Moderate) Azathioprine may interact with other drugs that are myelosuppressive. Drugs that may affect the production of leukocytes, including sulfamethoxazole; trimethoprim, SMX-TMP, may lead to exaggerated leukopenia, especially in patients who have received a renal transplant.
Azilsartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Azilsartan; Chlorthalidone: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Benazepril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Benazepril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Candesartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Candesartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Captopril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Captopril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Chlordiazepoxide; Amitriptyline: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Citric Acid; Potassium Citrate; Sodium Citrate: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Clomipramine: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Dapsone: (Major) Agranulocytosis has been reported in the second to third month of weekly concomitant treatment with dapsone and other hemolytic agents such as folic acid antagonists (e.g., trimethoprim, sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole). These combinations increase the likelihood of adverse hematologic events. Concurrent administration of dapsone with trimethoprim increases the plasma concentrations of both drugs. The efficacy of dapsone is increased, which may provide a therapeutic advantage in the treatment of Pneumocystis pneumonia; however, an increase in the frequency and severity of dapsone toxicity (methemoglobinemia, hemolytic anemia) also has been noted.
Desipramine: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Desogestrel; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Dextromethorphan; Guaifenesin; Potassium Guaiacolsulfonate: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Dienogest; Estradiol valerate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Digoxin: (Major) Monitor serum digoxin concentrations before initiating concomitant trimethoprim. Reduce digoxin concentrations by decreasing the dose by approximately 15% to 30% or by modifying the dosing frequency and continue monitoring. Concomitant use increased digoxin concentrations by 22% to 28%.
Dofetilide: (Contraindicated) Concomitant use of dofetilide with trimethoprim is contraindicated due to increased plasma concentrations of dofetilide, which may cause serious ventricular arrhythmias associated with QT prolongation, including torsade de pointes (TdP). Trimethoprim is an inhibitor of the renal cation transport system and decreases the active tubular secretion of dofetilide. The combination of trimethoprim 160 mg and 800 mg sulfamethoxazole co-administered twice daily with dofetilide 500 mcg for 4 days has been shown to increase dofetilide AUC by 93% and Cmax by 103%.
Donepezil; Memantine: (Moderate) Cationic drugs that are eliminated by renal tubular secretion, such as trimethoprim, may decrease memantine elimination by competing for common renal tubular transport systems. Although this interaction is theoretical, careful patient monitoring and dose adjustment of memantine and/or trimethoprim is recommended.
Doxepin: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Drospirenone: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Drospirenone; Estetrol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Drospirenone; Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Drospirenone; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Drospirenone; Ethinyl Estradiol; Levomefolate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available. (Minor) L-methylfolate and trimethoprim should be used together cautiously. Plasma concentrations of L-methylfolate may be reduced when used concomitantly with trimethoprim. Monitor patients for decreased efficacy of L-methylfolate if these agents are used together.
Elagolix; Estradiol; Norethindrone acetate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Eltrombopag: (Moderate) Eltrombopag is metabolized by CYP2C8. The significance of administering inhibitors of CYP2C8, such as trimethoprim, on the systemic exposure of eltrombopag has not been established. Monitor patients for signs of eltrombopag toxicity if these drugs are coadministered.
Enalapril, Enalaprilat: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Enalapril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Entecavir: (Moderate) Both entecavir and trimethoprim are secreted by active tubular secretion. In theory, coadministration of entecavir with trimethoprim may increase the serum concentrations of either drug due to competition for the drug elimination pathway.
Eplerenone: (Major) Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially with pre-existing risk factors for hyperkalemia. Trimethoprim should be used with caution with other drugs known to cause significant hyperkalemia such as eplerenone.
Eprosartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Eprosartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Estradiol; Levonorgestrel: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Estradiol; Norethindrone: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Estradiol; Norgestimate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Ethinyl Estradiol; Norelgestromin: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Ethinyl Estradiol; Norethindrone Acetate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Ethinyl Estradiol; Norgestrel: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Ethynodiol Diacetate; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Etonogestrel; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Finerenone: (Moderate) Monitor serum potassium concentrations closely if finerenone and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia. High doses of trimethoprim may increase the risk for hyperkalemia especially in patients with additional risk factors such as renal insufficiency.
Fluorouracil, 5-FU: (Major) Use of other folate antagonists should be avoided during therapy with trimethoprim. Hematologic toxicity can be increased by concurrent use of fluorouracil, 5-FU.
Folic Acid, Vitamin B9: (Minor) Folate antagonists, such as trimethoprim, especially when used in high doses or over a prolonged period, inhibit dihydrofolate reductase and thus may inhibit the action of folic acid, vitamin B9.
Fosinopril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Fosinopril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Fosphenytoin: (Moderate) Monitor phenytoin concentrations during concomitant therapy with fosphenytoin and trimethoprim due to risk for phenytoin toxicity. Concomitant use may increase phenytoin concentrations. Trimethoprim may inhibit the hepatic metabolism of phenytoin. Trimethoprim, given at a common clinical dosage, increased the phenytoin half-life by 51% and decreased the phenytoin metabolic clearance rate by 30%.
Ganciclovir: (Moderate) Use ganciclovir and sulfamethoxazole; trimethoprim together only if the potential benefits outweigh the risks; bone marrow suppression, spermatogenesis inhibition, skin toxicity, and gastrointestinal toxicity may be additive as both drugs inhibit rapidly dividing cells.
Hydrochlorothiazide, HCTZ; Moexipril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Ibritumomab Tiuxetan: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia. (Moderate) Use potassium phosphate cautiously with trimethoprim (especially high dose), as both drugs increase serum potassium concentrations. Concurrent use can cause hyperkalemia, especially in elderly patients or patients with impaired renal function. Monitor serum potassium concentrations at periodic intervals.
Imipramine: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Indinavir: (Minor) Concomitant administration of indinavir and trimethoprim should be done with caution. Administration of indinavir and sulfamethoxazole; trimethoprim, SMX-TMP significantly increased the AUC of trimethoprim. There was no effect on the AUC of indinavir or sulfamethoxazole.
Iodine; Potassium Iodide, KI: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Irbesartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Irbesartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Moderate) Rifampin is a potent enzyme inducer. Rifampin can increase the metabolism of sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole. A pharmacokinetic effect on the combination has been reported with another rifamycin. Concomitant administration of rifabutin and sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole (double-strength) in 12 HIV-infected patients decreased the AUC of SMX-TMP by about 15 to 20%. Rifabutin decreased the AUC and Cmax of trimethoprim by 14% and 6%, respectively, when rifabutin was given with trimethoprim alone. The drugs are often given clinically together with certain patient populations, so the ultimate clinical significance of a possible pharmacokinetic interaction is not clear. Monitor for therapeutic response to therapy.
Isoniazid, INH; Rifampin: (Moderate) Rifampin is a potent enzyme inducer. Rifampin can increase the metabolism of sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole. A pharmacokinetic effect on the combination has been reported with another rifamycin. Concomitant administration of rifabutin and sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole (double-strength) in 12 HIV-infected patients decreased the AUC of SMX-TMP by about 15 to 20%. Rifabutin decreased the AUC and Cmax of trimethoprim by 14% and 6%, respectively, when rifabutin was given with trimethoprim alone. The drugs are often given clinically together with certain patient populations, so the ultimate clinical significance of

a possible pharmacokinetic interaction is not clear. Monitor for therapeutic response to therapy.
Lamivudine, 3TC; Zidovudine, ZDV: (Moderate) Concomitant use of trimethoprim and zidovudine may result in additive hematological abnormalities. Use caution and monitor for hematologic toxicity during concurrent use.
Leucovorin: (Minor) Racemic leucovorin may be used to offset the toxicity of folate antagonists such as trimethoprim; however, the concomitant use of leucovorin with sulfamethoxazole; trimethoprim for the acute treatment of Pneumocystis carinii pneumonia in patients with HIV infection was associated with an increased risk of treatment failure and morbidity. Levoleucovorin may result in the same effect.
Leuprolide; Norethindrone: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Levoleucovorin: (Minor) Racemic leucovorin may be used to offset the toxicity of folate antagonists such as trimethoprim; however, the concomitant use of leucovorin with sulfamethoxazole; trimethoprim for the acute treatment of Pneumocystis carinii pneumonia in patients with HIV infection was associated with an increased risk of treatment failure and morbidity. Levoleucovorin may result in the same effect.
Levomefolate: (Minor) L-methylfolate and trimethoprim should be used together cautiously. Plasma concentrations of L-methylfolate may be reduced when used concomitantly with trimethoprim. Monitor patients for decreased efficacy of L-methylfolate if these agents are used together.
Levonorgestrel: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Levonorgestrel; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Levonorgestrel; Ethinyl Estradiol; Ferrous Bisglycinate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Levonorgestrel; Ethinyl Estradiol; Ferrous Fumarate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Lisinopril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Lisinopril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Losartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Losartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Mefenamic Acid: (Moderate) Mefenamic acid is a substrate for CYP450 2C9. Inhibitors of the 2C9 isoenzyme, such as trimethoprim, may lead to increased serum concentrations of mefenamic acid. If administered concurrently with mefenamic acid, monitor for NSAID related side effects.
Memantine: (Moderate) Cationic drugs that are eliminated by renal tubular secretion, such as trimethoprim, may decrease memantine elimination by competing for common renal tubular transport systems. Although this interaction is theoretical, careful patient monitoring and dose adjustment of memantine and/or trimethoprim is recommended.
Metformin; Repaglinide: (Major) Coadministration of trimethoprim and repaglinide increases the AUC of repaglinide by 61%; if coadministration is necessary, consider a dose reduction of repaglinide and increased frequency of glucose monitoring. Trimethoprim is a CYP2C8 inhibitor and repaglinide is a CYP2C8 substrate. The possibility of an increased risk of hypoglycemia should be considered during concomitant use of trimethoprim and repaglinide.
Metformin; Rosiglitazone: (Moderate) It is possible that an increase in the exposure of rosiglitazone may occur when coadministered with drugs that inhibit CYP2C8 such as trimethoprim. Patients should be monitored for changes in glycemic control if any CYP2C8 inhibitors are coadministered with rosiglitazone.
Methotrexate: (Major) Avoid concomitant use of methotrexate and trimethoprim due to the risk of severe methotrexate-related adverse reactions. If concomitant use is unavoidable, closely monitor for adverse reactions. Increased bone marrow suppression has been reported in patients receiving methotrexate and sulfamethoxazole; trimethoprim.
Moexipril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Nanoparticle Albumin-Bound Paclitaxel: (Moderate) Monitor for an increase in paclitaxel-related adverse reactions if coadministration of nab-paclitaxel with trimethoprim is necessary due to the risk of increased plasma concentrations of paclitaxel. Nab-paclitaxel is a CYP2C8 substrate and trimethoprim is a weak CYP2C8 inhibitor. In vitro, the metabolism of paclitaxel to 6-alpha-hydroxypaclitaxel was inhibited by another inhibitor of CYP2C8.
Nebivolol; Valsartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Norethindrone Acetate; Ethinyl Estradiol; Ferrous fumarate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Norethindrone: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Norethindrone; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Norethindrone; Ethinyl Estradiol; Ferrous fumarate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Norgestimate; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Norgestrel: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Nortriptyline: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Olmesartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Olmesartan; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Olmesartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Omeprazole; Amoxicillin; Rifabutin: (Moderate) Concomitant administration of rifabutin and sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole (double-strength) in 12 HIV-infected patients decreased the AUC of SMX-TMP by about 15 to 20%. Rifabutin decreased the AUC and Cmax of trimethoprim by 14% and 6%, respectively, when rifabutin was given with trimethoprim alone. Sulfamethoxazole; trimethoprim, SMX-TMP did not alter the pharmacokinetics of rifabutin.
Oral Contraceptives: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Paclitaxel: (Minor) Paclitaxel is a substrate of CYP2C8; in vitro, trimethoprim is a mild inhibitor of CYP2C8. If coadministration is necessary, use caution and monitor for increased paclitaxel side effects, including myelosuppression and peripheral neuropathy. This interaction may also be applicable to combination products containing trimethoprim, including sulfamethoxazole; trimethoprim (also known as SMX-TMP or cotrimoxazole).
Perindopril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Perindopril; Amlodipine: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Perphenazine; Amitriptyline: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Phenytoin: (Moderate) Monitor phenytoin concentrations during concomitant therapy with trimethoprim due to risk for phenytoin toxicity. Concomitant use may increase phenytoin concentrations. Trimethoprim may inhibit the hepatic metabolism of phenytoin. Trimethoprim, given at a common clinical dosage, increased the phenytoin half-life by 51% and decreased the phenytoin metabolic clearance rate by 30%.
Potassium Acetate: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Bicarbonate: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Chloride: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Citrate: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Citrate; Citric Acid: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Gluconate: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Iodide, KI: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium Phosphate: (Moderate) Use potassium phosphate cautiously with trimethoprim (especially high dose), as both drugs increase serum potassium concentrations. Concurrent use can cause hyperkalemia, especially in elderly patients or patients with impaired renal function. Monitor serum potassium concentrations at periodic intervals.
Potassium Phosphate; Sodium Phosphate: (Moderate) Use potassium phosphate cautiously with trimethoprim (especially high dose), as both drugs increase serum potassium concentrations. Concurrent use can cause hyperkalemia, especially in elderly patients or patients with impaired renal function. Monitor serum potassium concentrations at periodic intervals.
Potassium: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Potassium-sparing diuretics: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Pralatrexate: (Major) Renal elimination accounts for approximately 34% of the overall clearance of pralatrexate. Concomitant administration of drugs that undergo substantial renal clearance, such as sulfamethoxazole; trimethoprim, SMX-TMP, may result in delayed clearance of pralatrexate.
Procainamide: (Moderate) Monitor procainamide plasma concentrations, if available, and for clinical and ECG signs of procainamide toxicity with concomitant trimethoprim use. Trimethoprim increases the plasma concentrations of procainamide and its active N-acetyl metabolite (NAPA). The increased procainamide and NAPA plasma concentrations are associated with further prolongation of the QTc interval.
Protriptyline: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Pyrimethamine: (Major) Avoid concurrent use of trimethoprim and pyrimethamine. Reports suggest that patients receiving pyrimethamine as malaria prophylaxis in doses more than 25 mg/week may develop megaloblastic anemia with concurrent sulfamethoxazole; trimethoprim. Additionally, the concomitant use of other antifolic drugs associated with myelosuppression, including sulfamethoxazole; trimethoprim, may increase the risk of bone marrow suppression.
Quinapril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Quinapril; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Ramipril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Relugolix; Estradiol; Norethindrone acetate: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Repaglinide: (Major) Coadministration of trimethoprim and repaglinide increases the AUC of repaglinide by 61%; if coadministration is necessary, consider a dose reduction of repaglinide and increased frequency of glucose monitoring. Trimethoprim is a CYP2C8 inhibitor and repaglinide is a CYP2C8 substrate. The possibility of an increased risk of hypoglycemia should be considered during concomitant use of trimethoprim and repaglinide.
Rifabutin: (Moderate) Concomitant administration of rifabutin and sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole (double-strength) in 12 HIV-infected patients decreased the AUC of SMX-TMP by about 15 to 20%. Rifabutin decreased the AUC and Cmax of trimethoprim by 14% and 6%, respectively, when rifabutin was given with trimethoprim alone. Sulfamethoxazole; trimethoprim, SMX-TMP did not alter the pharmacokinetics of rifabutin.
Rifampin: (Moderate) Rifampin is a potent enzyme inducer. Rifampin can increase the metabolism of sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole. A pharmacokinetic effect on the combination has been reported with another rifamycin. Concomitant administration of rifabutin and sulfamethoxazole; trimethoprim, SMX-TMP, cotrimoxazole (double-strength) in 12 HIV-infected patients decreased the AUC of SMX-TMP by about 15 to 20%. Rifabutin decreased the AUC and Cmax of trimethoprim by 14% and 6%, respectively, when rifabutin was given with trimethoprim alone. The drugs are often given clinically together with certain patient populations, so the ultimate clinical significance of a possible pharmacokinetic interaction is not clear. Monitor for therapeutic response to therapy.
Rosiglitazone: (Moderate) It is possible that an increase in the exposure of rosiglitazone may occur when coadministered with drugs that inhibit CYP2C8 such as trimethoprim. Patients should be monitored for changes in glycemic control if any CYP2C8 inhibitors are coadministered with rosiglitazone.
Sacubitril; Valsartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Sapropterin: (Moderate) Drugs that inhibit folate metabolism, such as trimethoprim, should be used with caution in patients taking sapropterin. More frequent monitoring of blood phenylalanine concentrations is warranted in patients receiving these agents concurrently. An increased dosage of sapropterin may be necessary to achieve a biochemical response. Trimethoprim may decrease the bioavailability of endogenous tetrahydrobiopterin (BH4) by inhibiting the enzyme dihydrofolate reductase. Reduction of BH4 could make management of hyperphenylalaninemia with sapropterin more difficult.
Segesterone Acetate; Ethinyl Estradiol: (Moderate) It would be prudent to recommend alternative or additional contraception when oral contraceptives (OCs) are used in conjunction with antibiotics. It was previously thought that antibiotics may decrease the effectiveness of OCs containing estrogens due to stimulation of metabolism or a reduction in enterohepatic circulation via changes in GI flora. One retrospective study reviewed the literature to determine the effects of oral antibiotics on the pharmacokinetics of contraceptive estrogens and progestins, and also examined clinical studies in which the incidence of pregnancy with OCs and antibiotics was reported. It was concluded that the antibiotics ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline did not alter plasma concentrations of OCs. Antituberculous drugs (e.g., rifampin) were the only agents associated with OC failure and pregnancy. Based on the study results, these authors recommended that back-up contraception may not be necessary if OCs are used reliably during oral antibiotic use. Another review concurred with these data, but noted that individual patients have been identified who experienced significant decreases in plasma concentrations of combined OC components and who appeared to ovulate; the agents most often associated with these changes were rifampin, tetracyclines, and penicillin derivatives. These authors concluded that because females most at risk for OC failure or noncompliance may not be easily identified and the true incidence of such events may be under-reported, and given the serious consequence of unwanted pregnancy, that recommending an additional method of contraception during short-term antibiotic use may be justified. During long-term antibiotic administration, the risk for drug interaction with OCs is less clear, but alternative or additional contraception may be advisable in selected circumstances. Data regarding progestin-only contraceptives or for newer combined contraceptive deliveries (e.g., patches, rings) are not available.
Selexipag: (Major) Consider a less frequent dosing regimen (e.g., once daily) when initiating selexipag in patients receiving trimethoprim. Reduce the selexipag dose when trimethoprim is initiated in patients already taking selexipag. Coadministration can be expected to increase exposure to selexipag and its active metabolite. Selexipag is a substrate of CYP2C8; trimethoprim is a moderate CYP2C8 inhibitor.
Sodium picosulfate; Magnesium oxide; Anhydrous citric acid: (Major) Prior or concomitant use of antibiotics with sodium picosulfate; magnesium oxide; anhydrous citric acid may reduce efficacy of the bowel preparation as conversion of sodium picosulfate to its active metabolite bis-(p-hydroxy-phenyl)-pyridyl-2-methane (BHPM) is mediated by colonic bacteria. If possible, avoid coadministration. Certain antibiotics (i.e., tetracyclines and quinolones) may chelate with the magnesium in sodium picosulfate; magnesium oxide; anhydrous citric acid solution. Therefore, these antibiotics should be taken at least 2 hours before and not less than 6 hours after the administration of sodium picosulfate; magnesium oxide; anhydrous citric acid solution.
Sodium Sulfate; Magnesium Sulfate; Potassium Chloride: (Moderate) Monitor serum potassium concentrations closely if potassium supplements and trimethoprim are used together. Concomitant use may increase the risk of hyperkalemia.
Sofosbuvir; Velpatasvir: (Moderate) Use caution when administering velpatasvir with trimethoprim. Taking these drugs together may increase velpatasvir plasma concentrations, potentially resulting in adverse events. Velpatasvir is a CYP2C8 substrate; trimethoprim is an inhibitor of CYP2C8.
Sofosbuvir; Velpatasvir; Voxilaprevir: (Moderate) Use caution when administering velpatasvir with trimethoprim. Taking these drugs together may increase velpatasvir plasma concentrations, potentially resulting in adverse events. Velpatasvir is a CYP2C8 substrate; trimethoprim is an inhibitor of CYP2C8.
Sparsentan: (Moderate) Monitor potassium during concomitant use of sparsentan and trimethoprim. Concomitant use increases the risk for hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Spironolactone: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Spironolactone; Hydrochlorothiazide, HCTZ: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Telmisartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Telmisartan; Amlodipine: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Telmisartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Terbinafine: (Moderate) Due to the risk for terbinafine related adverse effects, caution is advised when coadministering trimethoprim. Although this interaction has not been studied by the manufacturer, and published literature suggests the potential for interactions to be low, taking these drugs together may increase the systemic exposure of terbinafine. Predictions about the interaction can be made based on the metabolic pathways of both drugs. Terbinafine is metabolized by at least 7 CYP isoenzymes, with major contributions coming from CYP2C8; trimethoprim is an inhibitor of this enzyme. Monitor patients for adverse reactions if these drugs are coadministered.
Tolbutamide: (Minor) Trimethoprim has been shown to reduce the clearance of unbound tolbutamide and prolong tolbutamide half-life. The reductions in tolbutamide clearance are relatively small. While the risk of enhanced hypoglycemic effects appears low, closely monitor blood glucose during concomitant therapy.
Trandolapril: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Trandolapril; Verapamil: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin-converting enzyme (ACE) inhibitor and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Triamterene: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Triamterene; Hydrochlorothiazide, HCTZ: (Moderate) Monitor serum potassium concentrations if trimethoprim and a potassium-sparing diuretic are used together. Concomitant use may increase the risk of hyperkalemia. The risk for trimethoprim-associated hyperkalemia is greatest in patients with additional risk factors for hyperkalemia such as age greater than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim.
Tricyclic antidepressants: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered with sulfamethoxazole; trimethoprim.
Trimipramine: (Moderate) Monitor therapeutic response and adjust the tricyclic antidepressant dose, if needed, when use sulfamethoxazole; trimethoprim concomitantly. The efficacy of tricyclic antidepressants can decrease when administered wi th sulfamethoxazole; trimethoprim.
Trospium: (Moderate) Both trospium and trimethoprim are eliminated by active renal tubular secretion; coadministration has the potential to increase serum concentrations of trospium or trimethoprim due to competition for the drug elimination pathway. Careful patient monitoring is recommended. For trospium, monitor for anticholinergic effects, such as dry mouth, constipation, blurred vision, urinary retention, or increased CNS effects which are not frequent when the drug is used alone. Trimethoprim dose-related side effects include nausea, vomiting, dizziness, headaches, mental depression/confusion, palpitations, and bone marrow depression. In some patients, a dosage reduction may be required.
Valganciclovir: (Moderate) Use valganciclovir and sulfamethoxazole; trimethoprim together only if the potential benefits outweigh the risks; bone marrow suppression, spermatogenesis inhibition, skin toxicity, and gastrointestinal toxicity may be additive as both drugs inhibit rapidly dividing cells.
Valproic Acid, Divalproex Sodium: (Minor) Use of other folate antagonists should be avoided during therapy with trimethoprim. Hematologic toxicity can be increased by concurrent use of divalproex or valproic acid.
Valsartan: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for hyperkalemia if concomitant use of an angiotensin II receptor antagonist and trimethoprim is necessary. Avoid concomitant use and consider alternative antibiotic therapy in patients with additional risk factors for hyperkalemia, including patients older than 65 years, those with underlying disorders of potassium metabolism, renal insufficiency, or those requiring high doses of trimethoprim. Amongst patients older than 65 years, concomitant use has been associated with a 2- to 7-fold increased risk of significant hyperkalemia compared to other antibiotics. Trimethoprim has a potassium-sparing effect on the distal nephron and may induce hyperkalemia, especially in those with pre-existing risk factors.
Zidovudine, ZDV: (Moderate) Concomitant use of trimethoprim and zidovudine may result in additive hematological abnormalities. Use caution and monitor for hematologic toxicity during concurrent use.

How Supplied

Primsol/TRIMPEX Oral Sol: 5mL, 50mg
Proloprim/Trimethoprim Oral Tab: 100mg

Maximum Dosage
Adults

200 mg/day PO is FDA-approved maximum dosage; however, doses up to 15 mg/kg/day PO have been used off-label for PCP in HIV-infected patients.

Geriatric

200 mg/day PO is FDA-approved maximum dosage; however, doses up to 15 mg/kg/day PO have been used off-label for PCP in HIV-infected patients.

Adolescents

400 mg/day PO is FDA-approved maximum dosage; however, doses up to 15 mg/kg/day PO have been used off-label for PCP in HIV-infected patients.

Children

10 mg/kg/day PO (Max: 400 mg/day) is FDA-approved maximum dosage; however, doses up to 15 mg/kg/day PO have been used off-label for PCP in HIV-infected patients.

Infants

6 to 11 months: 10 mg/kg/day PO is FDA-approved maximum dosage; however, doses up to 15 mg/kg/day PO have been used off-label for PCP in HIV-infected patients.
1 to 5 months: Safety and efficacy have not been established; however, doses up to 15 mg/kg/day PO have been used off-label for PCP in HIV-infected patients.

Neonates

Safety and efficacy have not been established.

Mechanism Of Action

Mechanism of Action: Trimethoprim interferes with folate synthesis in susceptible bacteria. It binds tightly to bacterial dihydrofolate reductase, thousands of times (about 50,000 times) more readily than to the same human enzyme. This action interferes with the uptake of p-aminobenzoic acid (PABA) into folic acid, an essential component of bacterial development. Folic acid is a coenzyme responsible for the transport of one-carbon fragments from one molecule to another and is crucial during the synthesis of thymidine, purines, and certain amino acids. Tetrahydrofolic acid, or THF, is the metabolically active form of folic acid. Other dihydrofolate reductase inhibitors include pyrimethamine, methotrexate, and trimetrexate, all of which are more potent than trimethoprim. Sulfonamides inhibit bacterial dihydrofolate synthetase, the enzyme immediately preceding dihydrofolate reductase. Thus, the combination of trimethoprim with a sulfonamide can produce a synergistic effect.Trimethoprim is used to treat bacterial urinary tract infections caused by Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter sp., and coagulase negative Staphylococcus species including S. saprophyticus. It also is effective against Pneumocystis and most strains of Haemophilus influenzae. Trimethoprim is not effective in treating Pseudomonas aeruginosa, and it is generally inactive against anaerobic bacteria. There are some resistant strains of gram-positive and gram-negative bacteria, notably some enterococci. Moraxella catarrhalis isolates were found to be consistently resistant to trimethoprim in vitro.Resistance to trimethoprim occurs through several mechanisms. Pseudomonas aeruginosa is intrinsically resistant to trimethoprim due to the drug's inability to penetrate the bacteria's cell wall. In other bacteria, resistance to trimethoprim may occur secondary to an increase in dihydrofolate reductase (DHFR) levels or activity or via an increase in the synthesis of DHFR, which reduces the susceptibility to trimethoprim.

Pharmacokinetics

Trimethoprim is administered orally. It distributes extensively into body tissues and fluids including the CSF and middle ear fluid. In children, following the administration of a single 4 mg/kg dose, the mean middle ear fluid concentration was 2 mcg/ml. Trimethoprim crosses the placenta, and is distributed into breast milk, prostatic fluid, and vaginal secretions at higher concentrations than those found in serum. It is about 45% bound to plasma protein.
 
Although there is some hepatic metabolism (10—20%) to inactive metabolites, most of the drug is renally excreted unchanged (60—80%) within 24 hours via glomerular filtration and tubular secretion. Serum half-life is 8—10 hours in patients with normal renal function. Acid urine increases and alkaline urine decreases excretion. Small amounts of the drug are excreted in the feces.
 
Affected cytochrome P450 isoenzymes and drug transporters:  CYP2C8, P-gp, OCT1, OCT2
Trimethoprim is an inhibitor of the hepatic isoenzyme CYP2C8 and the drug transporter OCT2. In vitro data suggest trimethoprim may be a substrate for P-glycoprotein (P-gp), OCT1, and OCT2.

Oral Route

Following oral administration, trimethoprim is rapidly absorbed from the GI tract and reaches peak serum concentrations within 1—4 hours, depending on dose. Repeated dosing results in serum concentrations that are greater (50%) than those observed with single-dose administration.

Pregnancy And Lactation
Pregnancy

Because trimethoprim may interfere with folic acid metabolism, use trimethoprim during pregnancy only if the potential benefit justifies the potential risk to the fetus.[48707] If trimethoprim is used during pregnancy, administer supplemental multivitamins.[30070] There are no large, well-controlled studies of trimethoprim use during human pregnancy. In a retrospective study of sulfamethoxazole; trimethoprim use in 186 pregnancies, the incidence of congenital abnormalities was 4.5% in mothers who received placebo and 3.3% in those receiving sulfamethoxazole; trimethoprim. There were no congenital abnormalities in those children (n = 10) whose mothers received sulfamethoxazole; trimethoprim during the first trimester. Additionally, in a separate survey, no congenital abnormalities were noted in children (n = 35) whose mothers received sulfamethoxazole; trimethoprim at the time of conception or shortly thereafter. Teratogenic effects have been noted in animal studies with trimethoprim doses 40-times the human dose.[48707]

Trimethoprim (TMP) is excreted in breast milk. Because trimethoprim may interfere with folate metabolism, use caution when trimethoprim is administered to breast-feeding woman.[48707] However, previous American Academy of Pediatrics (AAP) recommendations considered trimethoprim to be usually compatible with breast-feeding.[27500]