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# Septran (co-trimoxazole)
## Overview
Septran is a combination antibiotic containing sulfamethoxazole and trimethoprim. It is a bacteriostatic agent that inhibits folic acid synthesis, essential for bacterial growth.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PCP) prophylaxis and treatment
* Shigellosis
* Acute otitis media
* Traveler's diarrhea
## Adult Dosing
* **UTIs and Shigellosis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 12 hours for 3-7 days (UTIs) or 5 days (shigellosis).
* **PCP Treatment:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 6 hours for 14-21 days.
* **PCP Prophylaxis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) daily, or 3 times a week on non-consecutive days.
* **Traveler's Diarrhea:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 12 hours for 5 days.
## Pediatric Dosing
Dosing is based on trimethoprim weight-based recommendations.
* **General Infections:** 8-10 mg/kg/day of trimethoprim, divided into two doses, given every 12 hours. Maximum daily dose should not exceed 320 mg of trimethoprim.
* **PCP Treatment:** 15-20 mg/kg/day of trimethoprim, divided into four doses, given every 6 hours for 14-21 days.
* **PCP Prophylaxis:** 5-10 mg/kg/day of trimethoprim, divided into two doses, given every 12 hours.
* **Note:** Pediatric liquid formulations are available with different concentrations. Consult product labeling for exact volume.
## Dose Adjustments
* **Renal Impairment:** Adjust dose based on creatinine clearance (CrCl).
* CrCl > 30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Give usual dose every 12-18 hours.
* CrCl < 15 mL/min: Avoid use. If necessary, give usual dose every 24 hours.
## Contraindications
* Hypersensitivity to trimethoprim or sulfonamides.
* Documented megaloblastic anemia due to folate deficiency.
* Infants younger than 2 months (risk of kernicterus).
* Severe renal or hepatic impairment.
* History of drug-induced thrombocytopenia with either component.
## Adverse Effects
Common: Nausea, vomiting, rash, hyperkalemia.
Serious: Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), bone marrow suppression (anemia, leukopenia, thrombocytopenia), hyperkalemia, interstitial nephritis, hepatic dysfunction, crystalluria.
## 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.
* **Methotrexate:** May increase methotrexate levels and toxicity.
* **Sulfonylureas:** Increased risk of hypoglycemia.
* **Rifampin:** May decrease levels of sulfamethoxazole.
* **Potassium supplements:** Increased risk of hyperkalemia.
## Monitoring
* Complete blood counts (CBC) with differential, particularly with prolonged therapy or in immunocompromised patients.
* Renal and liver function tests.
* Electrolytes, especially potassium.
* Skin assessment for rash.
* For patients on warfarin, monitor INR.
## Clinical Pearls
* Ensure adequate fluid intake to prevent crystalluria.
* Sulfonamides are structurally related to some diuretics; caution in patients with sulfonamide allergies.
* Co-trimoxazole is a common cause of SJS/TEN; educate patients to report any rash immediately.
* The 1 DS tablet contains 800 mg sulfamethoxazole and 160 mg trimethoprim.
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*Disclaimer: This information is intended for clinical pharmacists and should not be used as a substitute for professional medical advice. Always consult the most current prescribing information and local protocols.*
