Septran%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252528co-Trimoxazole%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252529

# Septran (Co-Trimoxazole) ## Overview Septran is a combination antibiotic consisting of trimethoprim and sulfamethoxazole, acting synergistically to inhibit bacterial folate synthesis. ## Primary Indications * Urinary tract infections (UTIs) * Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment * Acute exacerbations of chronic bronchitis * Certain types of bacterial gastroenteritis ## Adult Dosing * **UTIs, Acute Exacerbations of Chronic Bronchitis, Bacterial Gastroenteritis:** Typically 160 mg trimethoprim/800 mg sulfamethoxazole (one double-strength tablet) twice daily for 3-14 days depending on indication. * **PJP Treatment:** 15-20 mg/kg/day trimethoprim component, divided into 3-4 doses, in combination with 75-100 mg/kg/day sulfamethoxazole component, divided into 4 doses, for 14-21 days. Maximum dose usually not to exceed 960 mg trimethoprim/4800 mg sulfamethoxazole per day. * **PJP Prophylaxis:** 160 mg trimethoprim/800 mg sulfamethoxazole (one double-strength tablet) daily, or 160 mg trimethoprim/800 mg sulfamethoxazole three times weekly (alternate day dosing). ## Pediatric Dosing Dosing is based on the trimethoprim component and varies by indication. * **General Infections (e.g., UTIs):** 8 mg/kg/day of trimethoprim, divided into two doses, given every 12 hours. Total daily dose of sulfamethoxazole is 40 mg/kg/day, divided into two doses. * **PJP Treatment:** 15-20 mg/kg/day of trimethoprim, divided into 3-4 doses, given every 6-8 hours. Total daily dose of sulfamethoxazole is 75-100 mg/kg/day, divided into 4 doses, given every 6 hours. * **PJP Prophylaxis:** 5 mg/kg/day of trimethoprim, divided into two doses, given every 12 hours. Total daily dose of sulfamethoxazole is 25 mg/kg/day, divided into two doses. *Note: For children under 2 months, safety and efficacy have not been established. Dosing for children should be calculated carefully based on weight and indication.* ## Dose Adjustments * **Renal Impairment:** * CrCl > 30 mL/min: No adjustment needed. * CrCl 15-30 mL/min: Reduce dose by 50%. * CrCl < 15 mL/min: Avoid use; if unavoidable, use with extreme caution and monitor drug levels. ## Contraindications * Hypersensitivity to trimethoprim or sulfamethoxazole. * History of drug-induced immune thrombocytopenia with either component. * Megaloblastic anemia due to folate deficiency. * Infants less than 2 months of age (due to risk of kernicterus). * Severe renal or hepatic failure when pharmacokinetic monitoring is not feasible. ## Adverse Effects Common adverse effects include rash, nausea, vomiting, diarrhea, and hyperkalemia. Serious adverse effects can include Stevens-Johnson syndrome, toxic epidermal necrolysis, severe hematologic reactions (agranulocytosis, aplastic anemia, thrombocytopenia), hepatotoxicity, and hyperkalemia. ## Key Drug Interactions * **Warfarin:** Increased INR. Monitor INR closely and adjust warfarin dose as needed. * **ACE inhibitors, ARBs, Potassium-Sparing Diuretics:** Increased risk of hyperkalemia. Monitor serum potassium. * **Methotrexate:** Increased risk of bone marrow suppression. Monitor CBC. * **Sulfonylureas (e.g., Glyburide, Glipizide):** May potentiate hypoglycemic effects. Monitor blood glucose. * **Cyclosporine:** Increased cyclosporine levels, potentially nephrotoxic. ## Monitoring * **Renal function:** Especially in patients with pre-existing renal impairment or those taking other nephrotoxic drugs. * **Complete Blood Count (CBC):** With differential and platelet count, particularly with prolonged therapy or in immunocompromised patients. * **Serum potassium:** Especially in patients with renal impairment or those taking other medications that affect potassium levels. * **Liver function tests:** If signs of hepatic impairment occur. ## Clinical Pearls * Encourage adequate fluid intake to prevent crystalluria. * Advise patients to report any rash, fever, sore throat, or signs of bleeding immediately. * Co-trimoxazole can interfere with certain laboratory tests (e.g., serum creatinine by the Jaffé method, leading to falsely elevated readings). *** **Disclaimer:** This information is for educational purposes and does not substitute for current prescribing information. Always verify the latest drug information with official product labeling and institutional guidelines before making clinical decisions.