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# Septran (Co-trimoxazole)
## Overview
Septran is a combination antibiotic containing trimethoprim and sulfamethoxazole. 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
* Certain respiratory and gastrointestinal infections
## Adult Dosing
* **Uncomplicated UTIs:** 1 DS (double-strength) tablet orally every 12 hours for 3 days.
* **PCP Treatment:** 15-20 mg/kg/day of trimethoprim component (e.g., 2 DS tablets every 6-8 hours) for 10-14 days.
* **PCP Prophylaxis:** 1 DS tablet orally once daily or 1 DS tablet twice daily, 3 times a week, depending on local protocol and indication.
* Other indications: Dosing varies widely based on the specific infection and severity. Typical doses range from 1 DS tablet every 12 hours to 2 DS tablets every 6-8 hours.
## Pediatric Dosing
* Dosing is based on the trimethoprim component, typically 5 mg/kg/dose of trimethoprim (equivalent to ~20-25 mg/kg/day of co-trimoxazole) administered every 12 hours.
* **PCP Treatment:** 15-20 mg/kg/day of trimethoprim component (e.g., 2 DS tablets every 6-8 hours) for 10-14 days.
* **PCP Prophylaxis:** 5 mg/kg/dose of trimethoprim component every 12 hours, or 150 mg/m²/day of trimethoprim component divided into two doses, 3 times a week.
* Actual doses should be calculated based on weight and the specific indication. Maximum adult doses should not be exceeded in children.
## Dose Adjustments
* **Renal Impairment:** Dose reduction is necessary.
* CrCl > 30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Administer 75% of the usual dose.
* CrCl < 15 mL/min: Avoid use. If unavoidable, administer 50% of the usual dose and monitor drug levels.
## 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 where urine or blood levels cannot be monitored.
* History of drug-induced thrombocytopenia with either agent.
## Adverse Effects
Common: Nausea, vomiting, rash (especially in HIV-infected patients), diarrhea.
Serious: Severe cutaneous reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis), hyperkalemia, bone marrow suppression (anemia, leukopenia, thrombocytopenia), renal impairment, hepatic dysfunction, photosensitivity.
## Key Drug Interactions
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Diuretics (especially thiazides):** Increased risk of hyperkalemia, particularly in elderly patients or those with renal impairment.
* **Warfarin:** Increased INR; monitor prothrombin time closely.
* **Methotrexate:** Increased risk of bone marrow suppression; monitor CBC.
* **Potassium supplements/Potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **Procainamide/Amantadine:** Increased serum concentrations; monitor for toxicity.
* **Cyclosporine:** Increased cyclosporine levels.
## Monitoring
* Complete blood counts (CBC) with differential, especially during prolonged therapy or in patients with G6PD deficiency.
* Renal and hepatic function tests.
* Serum electrolytes, particularly potassium.
* For patients with HIV, monitor for adverse reactions closely.
* If used in renal impairment, monitor drug levels.
## Clinical Pearls
* Encourage adequate fluid intake to prevent crystalluria.
* Advise patients to report any rash, sore throat, or fever immediately.
* Sulfonamides can displace bilirubin from albumin; caution in jaundiced infants and pregnant women near term.
* Discontinue at the first sign of rash, unless the rash is unequivocally not drug-related.
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*Please verify this information with the most current prescribing information and local protocols before use.*
