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# Septran (co-trimoxazole)
## Overview
Septran is a combination antibiotic containing trimethoprim and sulfamethoxazole. It is a broad-spectrum agent effective against many Gram-positive and Gram-negative bacteria.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PCP) prophylaxis and treatment
* Certain respiratory tract infections
* Certain gastrointestinal infections
## Adult Dosing
* **UTIs:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 12 hours for 3-7 days, depending on severity and organism.
* **PCP Prophylaxis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) daily or 3 times weekly.
* **PCP Treatment:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 6 hours for 14-21 days. Higher doses may be used for severe infections.
* **Other Infections:** Dosing varies widely; typically 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 12 hours. Maximum dose is generally 640 mg trimethoprim/3200 mg sulfamethoxazole (4 DS tablets) per day, divided every 6-12 hours.
## Pediatric Dosing
Dosing is based on trimethoprim component weight-based recommendations. Exact pediatric dosing often depends on local protocols and the specific indication.
* **General Infections:** 8 mg/kg trimethoprim and 40 mg/kg sulfamethoxazole per 24 hours, divided into two doses.
* **PCP Prophylaxis:** 5 mg/kg trimethoprim and 25 mg/kg sulfamethoxazole per 24 hours, divided into two doses, given daily or 3 times weekly.
* **PCP Treatment:** 15 mg/kg trimethoprim and 75 mg/kg sulfamethoxazole per 24 hours, divided into three or four doses.
**Note:** For children under 2 months, safety and efficacy are not established.
## Dose Adjustments
* **Renal Impairment:** Dosage adjustment is necessary for patients with significant renal impairment (CrCl < 15 mL/min). Consult prescribing information for specific guidance. Dose reduction is generally recommended for CrCl 15-30 mL/min.
## Contraindications
* Known hypersensitivity to trimethoprim or sulfonamides.
* Documented megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age (increased risk of kernicterus).
* Severe renal or hepatic insufficiency when pharmacokinetic monitoring is not feasible.
## Adverse Effects
Common: Rash, nausea, vomiting, diarrhea, pruritus, eosinophilia, increased liver enzymes.
Serious: Severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis), hyperkalemia, hyponatremia, crystalluria, blood dyscrasias (including anemia, leukopenia, thrombocytopenia), severe hepatic reactions, photosensitivity.
## Key Drug Interactions
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Methotrexate:** Increased risk of methotrexate-induced myelosuppression.
* **Potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Thiazide diuretics:** Increased risk of hyperkalemia in elderly patients.
* **Cyclosporine:** Increased cyclosporine levels with co-administration.
## Monitoring
* **Renal function:** Especially in patients with pre-existing renal disease or those taking other nephrotoxic agents.
* **Electrolytes:** Particularly potassium, especially in elderly patients or those with renal impairment.
* **Blood counts:** Complete blood count (CBC) with differential, particularly with prolonged use or in immunocompromised patients.
* **Liver function tests:** Baseline and periodic monitoring may be warranted.
* **Signs of hypersensitivity reactions:** Monitor closely for rash, fever, and other signs of severe allergic reactions.
## Clinical Pearls
* Ensure adequate hydration to prevent crystalluria.
* Administer with food or milk to minimize gastrointestinal upset.
* Co-trimoxazole is a known teratogen and should be avoided during the first trimester of pregnancy and at term.
* Elderly patients are at increased risk for adverse effects, particularly hyperkalemia and severe skin reactions.
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**Disclaimer:** This information is for educational purposes only and does not substitute professional medical advice. Always consult the current prescribing information and a healthcare professional for complete and up-to-date guidance before making any treatment decisions.
