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# Septran (Co-trimoxazole)
## Overview
Septran is a combination of sulfamethoxazole and trimethoprim, a sulfonamide and dihydrofolate reductase inhibitor, respectively. They work synergistically to inhibit bacterial folic acid synthesis.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Acute exacerbations of chronic bronchitis
* Shigellosis enteritis
* *Haemophilus influenzae* otitis media
## Adult Dosing
Dosing is typically based on the sulfamethoxazole component.
* **UTIs and acute exacerbations of chronic bronchitis:** 1 double-strength (DS) tablet (800 mg sulfamethoxazole/160 mg trimethoprim) every 12 hours for 7-14 days.
* **PJP Treatment:** 15 mg/kg/day of trimethoprim component, divided into 3-4 doses, given intravenously or orally for 14-21 days. This is typically 2 DS tablets every 8 hours.
* **PJP Prophylaxis:** 1 DS tablet once daily, or 1 DS tablet 3 times weekly (intermittent therapy).
## Pediatric Dosing
Dosing is based on the trimethoprim component.
* **General Infections:** 8 mg/kg/day of trimethoprim component, divided into 2 doses, given orally or intravenously. This is equivalent to approximately 40 mg/kg/day of sulfamethoxazole.
* Example: For a 20 kg child, this would be approximately 160 mg trimethoprim/day, divided into 2 doses. This could be given as 1 DS tablet every 12 hours.
* **PJP Treatment:** 15 mg/kg/day of trimethoprim component, divided into 3-4 doses.
* **PJP Prophylaxis:** 150 mg/m²/day of trimethoprim component, divided into 2 doses, given orally, 3 days per week.
*Note: Pediatric dosing may vary based on indication and local protocols. Always confirm specific pediatric recommendations.*
## Dose Adjustments
* **Renal Impairment (CrCl mL/min):**
* CrCl > 30: No adjustment needed.
* 15-30: Give usual dose every 12 hours.
* < 15: Give usual dose every 24 hours or withhold.
## 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).
* Severe renal or hepatic insufficiency when functional parameters cannot be monitored.
## Adverse Effects
* **Common:** Nausea, vomiting, rash (including Stevens-Johnson syndrome/toxic epidermal necrolysis, especially in HIV-infected patients), hyperkalemia, elevated liver enzymes.
* **Less Common:** Diarrhea, headache, dizziness, crystalluria (rare with adequate fluid intake), bone marrow suppression (leukopenia, thrombocytopenia, anemia).
## Key Drug Interactions
* **ACE inhibitors/ARBs/Potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **Warfarin:** Increased anticoagulant effect; monitor INR closely.
* **Methotrexate:** Increased risk of methotrexate toxicity; co-administration with leucovorin may be necessary for PJP treatment.
* **Diuretics (e.g., thiazides):** Increased risk of thrombocytopenia in elderly patients.
* **Cyclosporine:** Increased cyclosporine levels, particularly in transplant recipients.
* **Potassium supplements/Potassium-containing salt substitutes:** Increased risk of hyperkalemia.
## Monitoring
* Renal function (serum creatinine, CrCl).
* Electrolytes, especially potassium.
* Complete blood counts (CBC) with differential, particularly during prolonged therapy or in immunocompromised patients.
* Liver function tests.
* Signs of hypersensitivity reactions.
## Clinical Pearls
* Advise patients to maintain adequate fluid intake to prevent crystalluria.
* Discontinue if rash develops; severe dermatologic reactions can occur.
* Use with caution in patients with G6PD deficiency.
* Photosensitivity reactions are possible; advise sun protection.
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*Disclaimer: This information is intended for clinical use and does not replace comprehensive drug information resources. Always consult the most current prescribing information and relevant guidelines before making clinical decisions.*
