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# Septran (Co-trimoxazole)
## Overview
Septran is a combination antibiotic containing sulfamethoxazole and trimethoprim. It is a bacteriostatic agent that inhibits the synthesis of folic acid, which is essential for bacterial growth.
## Primary Indications
* Urinary Tract Infections (UTIs)
* Pneumocystis jirovecii pneumonia (PCP) prophylaxis and treatment
* Shigellosis
* *Stenotrophomonas maltophilia* infections
* Other susceptible bacterial infections
## Adult Dosing
* **Urinary Tract Infections (UTIs):**
* **Uncomplicated:** 1 double-strength (DS) tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily for 3-5 days.
* **Complicated:** 1 DS tablet twice daily for 7-14 days.
* **Pneumocystis jirovecii pneumonia (PCP) Treatment:** 15-20 mg/kg/day trimethoprim component, given in 3-4 divided doses, for 14-21 days. Maximum 800 mg trimethoprim component per dose.
* **PCP Prophylaxis:** 1 DS tablet once daily OR 1 DS tablet three times weekly.
* **Shigellosis:** 1 DS tablet twice daily for 5 days.
## Pediatric Dosing
Dosing is based on the trimethoprim component.
* **Urinary Tract Infections (UTIs) and Shigellosis:** 8 mg/kg/day trimethoprim component, divided into two doses, for 5-14 days. Maximum 400 mg trimethoprim component per dose.
* **Pneumocystis jirovecii pneumonia (PCP) Treatment:** 15-20 mg/kg/day trimethoprim component, divided into 3-4 doses, for 14-21 days. Maximum 800 mg trimethoprim component per dose.
* **PCP Prophylaxis:** 5 mg/kg/day trimethoprim component, divided into two doses, administered twice daily (e.g., Monday and Tuesday) for 3 days per week, OR 150 mg/m²/day trimethoprim component orally, divided into two doses, daily.
## Dose Adjustments
* **Renal Impairment (CrCl >30 mL/min):** No adjustment necessary.
* **Renal Impairment (CrCl 15-30 mL/min):** Give one-half of the usual dose.
* **Renal Impairment (CrCl <15 mL/min):** Avoid use or give one-fourth of the usual dose.
## Contraindications
* Known hypersensitivity to trimethoprim or sulfonamides.
* Documented megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age.
* Severe renal or hepatic insufficiency when pharmacokinetic monitoring is not feasible.
* History of drug-induced thrombocytopenia with use of trimethoprim or sulfonamides.
## Adverse Effects
* **Common:** Rash, nausea, vomiting, diarrhea, increased potassium.
* **Serious:** Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), aplastic anemia, agranulocytosis, severe hypersensitivity reactions, hyperkalemia, renal failure, hepatitis.
## 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.
* **Cyclosporine:** Increased risk of nephrotoxicity.
* **Digoxin:** Increased digoxin levels.
* **Potassium supplements, Potassium-containing salt substitutes:** Increased risk of hyperkalemia.
* **Sulfonylureas:** Increased risk of hypoglycemia.
## Monitoring
* Complete blood counts (CBC) with differential and platelet count, especially with prolonged therapy or in immunocompromised patients.
* Renal and liver function tests.
* Serum potassium levels.
* Fluid intake and urine output to prevent crystalluria.
## Clinical Pearls
* Instruct patients to drink plenty of fluids to prevent crystalluria.
* Advise patients to report any rash, sore throat, fever, or other signs of infection immediately.
* Discontinue if a rash develops.
* Trimethoprim can cause a false-positive serum creatinine test.
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*Disclaimer: This information is intended for healthcare professionals and should not be a substitute for professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment. Verify current prescribing information before making any clinical decisions.*
