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# Septran (Trimethoprim-sulfamethoxazole)
## Overview
Septran is a combination antibiotic containing trimethoprim and sulfamethoxazole in a fixed ratio of 1:5. 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
* Bacterial prostatitis
## Adult Dosing
* **Uncomplicated UTIs:** 1 double-strength (DS) tablet (160 mg trimethoprim/800 mg sulfamethoxazole) every 12 hours for 3-7 days.
* **Complicated UTIs, Shigellosis, Traveler's diarrhea:** 1 DS tablet every 12 hours for 7-14 days (duration varies by indication).
* **PCP Treatment:** 15 mg/kg/day of trimethoprim component, divided into 3-4 doses, given orally or IV. A common oral regimen is 2 DS tablets every 8 hours for 14-21 days.
* **PCP Prophylaxis:** 1 DS tablet once daily or 1 DS tablet three times a week.
## Pediatric Dosing
Dosing is based on the trimethoprim component.
* **General Infections (UTIs, otitis media):** 8 mg/kg/day of trimethoprim, divided into two doses, given every 12 hours.
* **For DS tablets:** The dose is approximately 1 DS tablet per 20 kg body weight every 12 hours. Maximum dose is 2 DS tablets every 12 hours.
* **PCP Treatment:** 20 mg/kg/day of trimethoprim, divided into four doses, given every 6 hours for 14-21 days.
* **PCP Prophylaxis:** 10 mg/kg/day of trimethoprim, divided into two doses, given every 12 hours, or 150 mg/m^2/day of trimethoprim orally in 2 divided doses.
## Dose Adjustments
* **Renal Impairment (CrCl > 30 mL/min):** No adjustment needed.
* **Renal Impairment (CrCl 15-30 mL/min):** Reduce usual dose by 50%.
* **Renal Impairment (CrCl < 15 mL/min):** Avoid use or administer at 25% of the usual dose given every 12 hours.
## Contraindications
* Known hypersensitivity to trimethoprim, sulfonamides, or any component of the formulation.
* Documented megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age (risk of kernicterus).
* Patients with severe renal insufficiency or hepatic insufficiency who cannot be monitored.
## Adverse Effects
Common: Rash, nausea, vomiting, diarrhea, pruritus, hyperkalemia.
Serious: Severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), severe hypersensitivity reactions, blood dyscrasias (anemia, leukopenia, thrombocytopenia), hepatotoxicity, hyperkalemia, hyponatremia, crystalluria.
## Key Drug Interactions
* **ACE inhibitors, ARBs, Potassium-sparing diuretics, Potassium supplements:** Increased risk of hyperkalemia.
* **Warfarin:** Increased INR. Monitor INR closely.
* **Methotrexate:** Increased methotrexate levels and potential for toxicity. Concurrent use generally avoided unless co-administered with leucovorin.
* **Cyclosporine:** Increased cyclosporine levels, particularly in transplant patients.
* **Digoxin:** Increased digoxin levels.
* **Thiazide diuretics:** Increased risk of hyperkalemia, especially in elderly patients.
* **Repaglinide, Glipizide, Glyburide:** Increased risk of hypoglycemia.
## Monitoring
* Complete blood counts (CBC) with differential, particularly with prolonged therapy or in immunocompromised patients.
* Renal and liver function tests.
* Serum electrolytes, especially potassium.
* Signs of hypersensitivity or skin reactions.
## Clinical Pearls
* Advise patients to drink plenty of fluids to prevent crystalluria.
* Discontinue immediately if a rash develops.
* Caution with G6PD deficiency, as sulfonamides can cause hemolytic anemia.
* May increase serum creatinine without affecting GFR due to inhibition of tubular secretion.
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*This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines before making clinical decisions.*
