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# Septran (Co-Trimoxazole)
## Overview
Co-trimoxazole is a combination of trimethoprim and sulfamethoxazole, a synergistic antimicrobial agent.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Shigellosis
* Acute otitis media
* Traveler's diarrhea
## Adult Dosing
* **UTIs:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 12 hours for 3-7 days.
* **PJP Treatment:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 6-8 hours for 14-21 days.
* **PJP Prophylaxis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) daily or 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) three times weekly.
* **Shigellosis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 12 hours for 5 days.
* **Traveler's Diarrhea:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 12 hours for 3-5 days.
* **Maximum dose:** Generally limited to 160 mg trimethoprim/800 mg sulfamethoxazole (1 double-strength tablet) every 8 hours for severe infections, but depends on indication and renal function.
## Pediatric Dosing
Dosing is based on trimethoprim component, typically 5-10 mg/kg/day divided every 12 hours for UTIs and other common infections. For PJP, doses are higher (15-20 mg/kg/day of trimethoprim). Exact pediatric dosing often depends on specific indication and local protocols. Oral suspension typically contains 40 mg trimethoprim and 200 mg sulfamethoxazole per 5 mL.
## Dose Adjustments
* **Renal Impairment:** Adjust dose based on creatinine clearance. In adults with CrCl <15 mL/min, use is generally contraindicated. CrCl 15-30 mL/min: administer 75% of standard dose. CrCl 30-45 mL/min: administer 50% of standard dose. CrCl 45-60 mL/min: administer 75% of standard dose.
## Contraindications
* Known hypersensitivity to trimethoprim or sulfonamides.
* Megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age (risk of kernicterus).
* Severe renal or hepatic impairment.
## Adverse Effects
* **Common:** Rash, pruritus, nausea, vomiting, diarrhea.
* **Serious:** Severe cutaneous reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), hyperkalemia, bone marrow suppression (anemia, leukopenia, thrombocytopenia), hepatic dysfunction, crystalluria (ensure adequate hydration).
## Key Drug Interactions
* **Warfarin:** Increased INR; monitor INR closely.
* **ACE Inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Diuretics (especially thiazides):** Increased risk of hyperkalemia and thrombocytopenia in elderly patients.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Potassium supplements:** Increased risk of hyperkalemia.
* **Cyclosporine:** Increased cyclosporine levels.
## Monitoring
* **Renal function:** Especially with pre-existing renal disease or concurrent nephrotoxic agents.
* **Electrolytes:** Particularly potassium.
* **Complete blood count (CBC):** Monitor for hematologic changes, especially with prolonged therapy or in immunocompromised patients.
* **Liver function tests:** Monitor if indicated.
* **Hydration status:** Crucial to prevent crystalluria.
## Clinical Pearls
* Administer with food or milk to minimize GI upset.
* Ensure adequate fluid intake to prevent crystalluria.
* Sulfonamides can displace bilirubin from albumin; use with caution in neonates and patients with hyperbilirubinemia.
* Monitor for signs of hypersensitivity reactions, which can be severe.
* Consider folate supplementation for patients on long-term therapy, especially those with risk factors for folate deficiency.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for definitive guidance. This information does not replace professional medical judgment.*
