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# Septran (Co-Trimoxazole)
## Overview
Septran is a combination antibiotic containing trimethoprim and sulfamethoxazole. It is a broad-spectrum bacteriostatic agent that inhibits folic acid synthesis.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* *Shigella* enteritis
* *Haemophilus influenzae* otitis media
* Traveler's diarrhea (caused by enterotoxigenic *E. coli*)
## Adult Dosing
* **Uncomplicated UTIs:** 1 double-strength (DS) tablet (800 mg sulfamethoxazole/160 mg trimethoprim) twice daily for 3 days.
* **PJP Treatment:** 15-20 mg/kg/day (trimethoprim component) divided into 3-4 doses for 14-21 days. Equivalently, 2 DS tablets every 8 hours.
* **PJP Prophylaxis:** 1 DS tablet once daily. Alternatively, 1 DS tablet three times weekly.
* **Shigellosis/Traveler's Diarrhea:** 1 DS tablet twice daily for 5 days.
Maximum daily dose: Generally not to exceed 8 DS tablets per day (640 mg trimethoprim/3200 mg sulfamethoxazole).
## Pediatric Dosing
Dosing is typically based on the trimethoprim component.
* **UTIs/Shigellosis:** 8-10 mg/kg/day (trimethoprim component) divided into two doses.
* For a DS tablet (160 mg trimethoprim/800 mg sulfamethoxazole): approximately 1/2 DS tablet per 20 kg body weight, given twice daily.
* **PJP Treatment:** 15-20 mg/kg/day (trimethoprim component) divided into 3-4 doses for 14-21 days.
* **PJP Prophylaxis:** 5 mg/kg/day (trimethoprim component) divided into two doses, given once daily, three times a week.
*Note: Pediatric dosing for Septran suspensions often depends on the specific concentration available. Always refer to the product labeling.*
## Dose Adjustments
* **Renal Impairment:**
* CrCl > 30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Administer 75% of the usual dose.
* CrCl < 15 mL/min: Avoid use or administer 50% of the usual dose every 12 hours.
## Contraindications
* Known hypersensitivity to trimethoprim or sulfonamides.
* Documented early infancy (less than 2 months of age) due to risk of kernicterus.
* Megaloblastic anemia due to folate deficiency.
* Severe renal insufficiency where urine output cannot be monitored.
* History of drug-induced thrombocytopenia with either component.
## Adverse Effects
* **Common:** Nausea, vomiting, rash (including Stevens-Johnson syndrome/toxic epidermal necrolysis, especially in patients with AIDS), hyperkalemia, elevated creatinine.
* **Less Common:** Diarrhea, pruritus, urticaria, dizziness, headache, leukopenia, neutropenia, thrombocytopenia, eosinophilia, elevated liver enzymes.
## Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely and adjust warfarin dose as needed.
* **Methotrexate:** Increased risk of bone marrow suppression.
* **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia.
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Sulfonylureas (oral hypoglycemics):** Potentiated hypoglycemic effect.
* **Cyclosporine:** Increased cyclosporine levels, particularly in transplant recipients.
* **Digoxin:** Increased digoxin levels, especially in elderly patients or those with renal impairment.
* **Tricyclic Antidepressants (TCAs):** May decrease the efficacy of TCAs.
## Monitoring
* Renal function (serum creatinine, GFR).
* Complete blood count (CBC) with differential, particularly with prolonged therapy or in immunocompromised patients.
* Electrolytes (especially potassium).
* Liver function tests.
* For patients on warfarin, monitor INR.
* Monitor for signs of hypersensitivity reactions.
## Clinical Pearls
* Advise patients to drink plenty of fluids to prevent crystalluria.
* Co-trimoxazole can interfere with urine glucose and protein tests.
* Photosensitivity can occur; advise patients to use sun protection.
* Co-trimoxazole is generally avoided in the first trimester of pregnancy due to potential teratogenicity. It may be used in the third trimester if benefits outweigh risks, but caution is advised near term due to the risk of kernicterus in neonates.
* The oral suspension is often preferred for pediatric patients, especially for PJP prophylaxis due to palatability.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines before making clinical decisions.*
