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# Septran (Trimethoprim/Sulfamethoxazole)
## Overview
Septran is a combination antibiotic containing trimethoprim and sulfamethoxazole in a 1:5 ratio. It is a sulfonamide with bacteriostatic activity.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Acute otitis media
* Traveler's diarrhea
* Shigellosis
* Bronchitis (acute exacerbations)
* Prostatitis
## Adult Dosing
* **Urinary Tract Infections and Shigellosis:** 160 mg trimethoprim/800 mg sulfamethoxazole (1 DS tablet) every 12 hours for 3-7 days (UTI) or 5 days (shigellosis).
* **Pneumocystis jirovecii Pneumonia (Treatment):** 15-20 mg/kg/day trimethoprim component, divided into 3-4 doses, for 14-21 days. This typically translates to 2 DS tablets every 6 hours.
* **Pneumocystis jirovecii Pneumonia (Prophylaxis):** 1 DS tablet daily, or 1 DS tablet three times weekly (alternating days).
* **Traveler's Diarrhea:** 1 DS tablet every 12 hours for 3-5 days.
* **Acute Otitis Media:** 10 mg/kg/day trimethoprim component, divided into two doses, for 10 days.
* **Acute Exacerbations of Chronic Bronchitis:** 1 DS tablet every 12 hours for 7 days.
Maximum dose: Generally no more than 8 DS tablets per day.
## Pediatric Dosing
Dosing is based on the trimethoprim component, typically 15-20 mg/kg/day, divided every 12 hours, unless otherwise specified.
* **Urinary Tract Infections:** 8 mg/kg/day trimethoprim component, divided into two doses, for 10 days. Example: For a 20 kg child, approximately 80 mg of trimethoprim daily, given as 40 mg every 12 hours. This would correspond to approximately 1/2 to 1 teaspoon of the oral suspension (concentration varies by product).
* **Pneumocystis jirovecii Pneumonia (Treatment):** 15-20 mg/kg/day trimethoprim component, divided into 3-4 doses, for 14-21 days.
* **Pneumocystis jirovecii Pneumonia (Prophylaxis):** 5 mg/kg/day trimethoprim component, divided into two doses, on days when prophylaxis is given.
* **Shigellosis:** 10 mg/kg/day trimethoprim component, divided into two doses, for 5 days.
* **Traveler's Diarrhea:** 8 mg/kg/day trimethoprim component, divided into two doses, for 3-5 days.
Note: Pediatric dosing can be complex and depends on the specific indication and age/weight. Always consult pediatric guidelines or protocols.
## Dose Adjustments
* **Renal Impairment:** Adjust dose based on creatinine clearance (CrCl).
* CrCl > 30 mL/min: Usual dose.
* CrCl 15-30 mL/min: Half the usual dose every 12-18 hours.
* CrCl < 15 mL/min: Avoid use or give 1/4 the usual dose every 24 hours.
## Contraindications
* Documented hypersensitivity to trimethoprim, sulfamethoxazole, or other sulfonamides.
* Infants less than 2 months of age (risk of kernicterus).
* Marked liver or kidney damage.
* Megaloblastic anemia due to folate deficiency.
* Porphyria.
## Adverse Effects
* **Common:** Nausea, vomiting, rash, hyperkalemia, elevated liver enzymes.
* **Serious:** Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), severe rash (e.g., DRESS), bone marrow suppression (anemia, leukopenia, thrombocytopenia), hyperkalemia (potentially life-threatening), interstitial nephritis, crystalluria, hepatotoxicity, photosensitivity.
## Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely and adjust warfarin dose as needed.
* **ACE inhibitors/ARBs/Potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **Methotrexate:** Increased methotrexate levels and toxicity. Avoid concurrent use or monitor methotrexate levels and blood counts closely.
* **Potassium supplements/Potassium-containing salt substitutes:** Increased risk of hyperkalemia.
* **Digoxin:** Potential for increased digoxin levels. Monitor digoxin levels.
* **Cyclosporine:** Increased cyclosporine levels and nephrotoxicity.
* **Sulfonylureas:** Increased risk of hypoglycemia.
* **Tricyclic Antidepressants (TCAs):** Potential for reduced efficacy of TCAs.
## Monitoring
* **Renal function (BUN, creatinine)**
* **Electrolytes (especially potassium)**
* **Complete blood count (CBC) with differential** (particularly with prolonged therapy or in immunocompromised patients)
* **Liver function tests (LFTs)**
* **Hydration status and urine output** (to prevent crystalluria)
* **INR** (if on warfarin)
## Clinical Pearls
* Adequate fluid intake is crucial to prevent crystalluria, especially in patients with renal impairment.
* Sulfonamides can cause photosensitivity; advise patients to use sun protection.
* Trimethoprim can cause a reversible, asymptomatic increase in serum creatinine due to inhibition of tubular secretion. This is not indicative of actual renal dysfunction but should be noted.
* Discontinue the drug immediately if a rash develops.
* Folic acid supplementation (600 mcg daily) may be considered for patients on long-term therapy or with risk factors for folate deficiency.
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*Disclaimer: This information is intended for clinical professionals. Always consult the most current prescribing information, local protocols, and patient-specific factors before making clinical decisions.*
