Susceptible infections including UTIs (not for initial uncomplicated episodes), shigellosis, prophylaxis and treatment of Pneumocystis jiroveci pneumonia (PJP), travelers' diarrhea or acute exacerbations of chronic bronchitis in adults, acute otitis media in children.
1 DS tab or 2 regular tabs every 12 hours for 5 days (shigellosis, travelers' diarrhea), or 10–14 days (UTIs), or 14 days (bronchitis). PJP treatment: 15–20mg/kg per day trimethoprim (75–100mg/kg per day sulfamethoxazole) in equally divided doses every 6 hours for 14–21 days; PJP prophylaxis: one DS tab daily. Renal impairment (CrCl 15–30mL/min): reduce dose by ½; CrCl <15mL/min: not recommended.
<2months: see Contraindications. ≥2months: 8mg/kg per day trimethoprim (40mg/kg per day of sulfamethoxazole) in 2 divided doses at 12 hour intervals for 5 days (shigellosis) or 10 days (otitis media, UTIs). PJP treatment: as adult; PJP prophylaxis or renal impairment: see full labeling.
Sulfonamide + folic acid inhibitor.
History of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides. Megaloblastic anemia due to folate deficiency. Children <2 months. Marked hepatic damage. Severe renal insufficiency when renal status cannot be monitored.
Not for group A β-hemolytic strep. Avoid prolonged administration. Monitor CBCs, urine, and renal function. Hepatic or renal dysfunction. AIDS (increased risk of toxicities). Folate or G6PD deficiency. Severe allery or bronchial asthma. Malnutrition. Porphyria. Thyroid dysfunction. Disorders of potassium metabolism. Monitor for electrolyte abnormalities. Maintain adequate hydration. Discontinue if rash occurs. Elderly. Pregnancy (Cat.D). Nursing mothers.
Caution with concomitant CYP2C8, 2C9, or OCT2 substrates. May potentiate oral anticoagulants (eg, warfarin), hypoglycemics, phenytoin, methotrexate, digoxin. May be potentiated by indomethacin. May increase risk of thrombocytopenia with diuretics (esp. thiazides). Nephrotoxicity with cyclosporine in renal transplant. Megaloblastic anemia with >25mg/week doses of pyrimethamine. May antagonize tricyclic antidepressants. May interfere with assays for serum methotrexate, creatinine. PJP treatment: avoid leucovorin.
GI upset, allergic skin reactions, blood dyscrasias (eg, megaloblastic anemia), hemolysis, hepatic or renal toxicity, crystalluria, pancreatitis, photosensitivity, drug fever, rash (may be serious, eg, Stevens-Johnson syndrome, toxic epidermal necrolysis), lupus-like syndrome, peripheral neuritis, depression, convulsions, ataxia, hypoglycemia, hyperkalemia, hyponatremia; C. difficile associated diarrhea.