Septran%2525252525252525252525252525252525252525252525252525252525252525252525252525252525252520%2525252525252525252525252525252525252525252525252525252525252525252525252525252525252528co-Trimoxazole%2525252525252525252525252525252525252525252525252525252525252525252525252525252525252529

# Septran (Co-trimoxazole) ## Overview Co-trimoxazole is a combination antibiotic consisting of sulfamethoxazole and trimethoprim. It acts by inhibiting folic acid synthesis, which is essential for bacterial growth. ## Primary Indications * Urinary tract infections (UTIs) * Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment * *Shigella* enteritis * *Stenotrophomonas maltophilia* infections * *Listeria monocytogenes* infections ## Adult Dosing * **Uncomplicated UTIs:** 1 double-strength (DS) tablet (800 mg sulfamethoxazole / 160 mg trimethoprim) every 12 hours for 3 days. * **Complicated UTIs/Prostatitis:** 1 DS tablet every 12 hours for 10-14 days. * **PJP Treatment:** 15 mg/kg/day trimethoprim component, divided into 3-4 doses, for 14-21 days. (e.g., 2 DS tablets every 8 hours). * **PJP Prophylaxis:** 1 DS tablet daily, or 1 DS tablet three times weekly. * **Shigellosis:** 1 DS tablet every 12 hours for 5 days. * Maximum dose: Generally, no more than 8 DS tablets (640 mg trimethoprim/3200 mg sulfamethoxazole) per day. ## Pediatric Dosing Dosing is based on the trimethoprim component, typically 5-10 mg/kg/day for UTIs, divided into two doses. For PJP treatment, 15-20 mg/kg/day trimethoprim component, divided into 3-4 doses. * **General infections:** 8 mg/kg/day of trimethoprim component, divided into 2 doses. * **PJP Treatment:** 15-20 mg/kg/day of trimethoprim component, divided into 3-4 doses. * **PJP Prophylaxis:** 5 mg/kg/day of trimethoprim component, divided into 2 doses. * *Note: Specific pediatric dosing often relies on local protocols and clinical guidelines due to product availability (e.g., suspension vs. DS tablets).* ## Dose Adjustments * **Renal Impairment:** Dose adjustment is necessary for CrCl < 30 mL/min. Consult product labeling or renal dosing guidelines. * CrCl 15-30 mL/min: Give 75% of the usual dose. * CrCl < 15 mL/min: Give 50% of the usual dose every 12 hours. * **Hepatic Impairment:** No specific guidelines, use with caution. ## Contraindications * Known hypersensitivity to trimethoprim or sulfonamides. * History of drug-induced immune thrombocytopenia with previous use of trimethoprim or sulfonamides. * Megaloblastic anemia due to folate deficiency. * Premature infants and infants up to 2 months of age (risk of kernicterus). * Severe renal insufficiency where urine output cannot be monitored. * Severe hepatic insufficiency. ## Adverse Effects * **Common:** Rash, pruritus, nausea, vomiting, diarrhea. * **Serious:** * Hypersensitivity reactions (including Stevens-Johnson syndrome and toxic epidermal necrolysis). * Hematologic abnormalities (anemia, leukopenia, thrombocytopenia, agranulocytosis, aplastic anemia). * Hyperkalemia. * Hepatotoxicity. * Renal crystalluria (ensure adequate fluid intake). * Photosensitivity. * *Clostridioides difficile*-associated diarrhea. ## Key Drug Interactions * **Warfarin:** Increased INR; monitor INR closely. * **Methotrexate:** Increased methotrexate levels and toxicity. * **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia. * **ACE inhibitors and ARBs:** Increased risk of hyperkalemia. * **Digoxin:** May increase digoxin levels. * **Rifampin:** May decrease co-trimoxazole levels. * **Cyclosporine:** May increase cyclosporine levels. * **Oral hypoglycemics:** Increased risk of hypoglycemia. ## Monitoring * Complete blood counts (CBC) with differential, especially with prolonged therapy or in immunocompromised patients. * Renal function (BUN, creatinine). * Electrolytes (especially potassium). * Liver function tests. * Signs and symptoms of hypersensitivity reactions. * For patients on warfarin, monitor INR. ## Clinical Pearls * Encourage adequate fluid intake to prevent crystalluria. * Advise patients to report any new rashes, fever, sore throat, or other signs of infection immediately. * Co-trimoxazole can interfere with some urine glucose tests. * Discontinue at the first sign of rash. * Can be used for PJP prophylaxis in HIV-infected patients and for Pneumocystis pneumonia treatment. **Disclaimer:** This information is for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and local institutional protocols before making any treatment decisions.