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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.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Shigellosis
* Acute otitis media
## Adult Dosing
* **UTI:** 1 double-strength (DS) tablet (160 mg trimethoprim/800 mg sulfamethoxazole) every 12 hours for 3-7 days for uncomplicated UTIs. For complicated UTIs, duration may be longer.
* **PJP Treatment:** 15 mg/kg (trimethoprim component) per day divided into 3-4 doses (e.g., 2 DS tablets every 6 hours) for 14-21 days.
* **PJP Prophylaxis:** 1 DS tablet daily, or 1 DS tablet three times weekly, depending on local protocols and patient risk.
* **Shigellosis:** 1 DS tablet every 12 hours for 5 days.
* **Acute Otitis Media:** 40 mg/kg (trimethoprim component) per day divided into two doses, not to exceed 800 mg sulfamethoxazole per dose, for 10 days.
## Pediatric Dosing
Dosing is based on the trimethoprim component (10 mg/kg/day to 20 mg/kg/day divided into 2-4 doses). Pediatric dosing for specific indications can vary significantly and should be guided by weight and indication. Consult specific guidelines for pediatric PJP prophylaxis/treatment and UTI management. Maximum daily trimethoprim dose is typically 800 mg, and sulfamethoxazole is 4000 mg.
## Dose Adjustments
* **Renal Impairment:**
* CrCl >30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Give 75% of the usual dose every 12 hours.
* CrCl <15 mL/min: Contraindicated for prolonged use; consider alternative if used for short-term therapy.
## Contraindications
* Known hypersensitivity to trimethoprim, sulfonamides, or any component of the formulation.
* Megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age (risk of kernicterus).
* Severe renal or hepatic insufficiency when pharmacokinetic monitoring is not feasible.
## Adverse Effects
Common: Rash, nausea, vomiting, diarrhea, pruritus.
Serious: Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), exfoliative dermatitis, severe hematologic reactions (agranulocytosis, aplastic anemia, thrombocytopenia), hyperkalemia, C. difficile-associated diarrhea, photosensitivity.
## Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely.
* **ACE inhibitors/ARBs/Potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **Methotrexate:** Increased methotrexate levels and toxicity.
* **Sulfonylureas:** Enhanced hypoglycemic effect.
* **Rifampin:** May increase elimination of trimethoprim.
* **Digoxin:** May increase digoxin levels.
## Monitoring
* Renal function (serum creatinine).
* Electrolytes (especially potassium).
* Complete blood counts (CBC) with differential and platelet count, particularly with prolonged use or in patients with G6PD deficiency.
* Signs of hypersensitivity reactions.
## Clinical Pearls
* Administer with adequate fluid intake to prevent crystalluria.
* Trimethoprim can cause a false-positive result for urinary THC screening.
* Rash is a common and potentially serious adverse effect; discontinue immediately if severe rash occurs.
* Dosing for prophylaxis in immunocompromised patients may follow specific institutional protocols.
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*This information is intended for healthcare professionals. Always verify current prescribing information with the official drug product labeling and institutional protocols.*
