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# Septran (Trimethoprim/Sulfamethoxazole)
## Overview
Septran is a combination antibiotic consisting of trimethoprim and sulfamethoxazole in a 1:5 ratio. It is a synthetic antibacterial agent.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Bacterial gastroenteritis
* Acute otitis media
* Acute exacerbations of chronic bronchitis
## Adult Dosing
* **Uncomplicated UTIs:** 1 double-strength (DS) tablet (160 mg trimethoprim/800 mg sulfamethoxazole) orally every 12 hours for 3 days.
* **PJP Treatment:** 15 to 20 mg/kg trimethoprim component per day, divided into 3 or 4 doses, with 75 to 100 mg/kg sulfamethoxazole component per day, divided into 3 or 4 doses. Maximum dose: 16 DS tablets (960 mg trimethoprim/4800 mg sulfamethoxazole) per day.
* **PJP Prophylaxis:** 1 DS tablet (160 mg trimethoprim/800 mg sulfamethoxazole) orally once daily, or 1 single-strength tablet (80 mg trimethoprim/400 mg sulfamethoxazole) orally twice daily.
* **Other Infections:** Dosing varies depending on the infection and severity. Common adult dosing for susceptible infections is 1 DS tablet (160 mg trimethoprim/800 mg sulfamethoxazole) every 12 hours.
## Pediatric Dosing
Dosing is based on the trimethoprim component and is typically 8 mg/kg/day divided into two doses.
* **PJP Treatment:** 20 mg/kg trimethoprim component/day and 100 mg/kg sulfamethoxazole component/day, divided into 4 doses.
* **PJP Prophylaxis:** 10 mg/kg trimethoprim component/day and 50 mg/kg sulfamethoxazole component/day, divided into 2 doses.
* **Other Infections:** 8 mg/kg trimethoprim component/day divided into 2 doses.
Specific tablet strengths should be used for accurate pediatric dosing, and dosing should not exceed adult maximums.
## Dose Adjustments
* **Renal Impairment:** Adjust dose based on creatinine clearance (CrCl).
* CrCl > 30 mL/min: Standard dose.
* CrCl 15-30 mL/min: Half of the standard dose.
* CrCl < 15 mL/min: Contraindicated.
* **Hepatic Impairment:** Use with caution; dose adjustment may be necessary.
## Contraindications
* Known hypersensitivity to trimethoprim or sulfamethoxazole.
* Documented hypersensitivity to sulfonamides.
* Megaloblastic anemia due to folate deficiency.
* Infants less than 2 months of age (risk of kernicterus).
* Severe renal insufficiency where urine output cannot be monitored.
* Marked liver damage.
## Adverse Effects
Common: Rash, nausea, vomiting, diarrhea, anorexia.
Serious: Stevens-Johnson syndrome, toxic epidermal necrolysis, hypersensitivity reactions (including anaphylaxis), blood dyscrasias (aplastic anemia, agranulocytosis, thrombocytopenia, leukopenia), hyperkalemia, acute renal failure, hepatitis, photosensitivity.
## Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely and adjust warfarin dose.
* **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia.
* **Methotrexate:** Increased risk of methotrexate toxicity (myelosuppression).
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Oral hypoglycemics:** Increased risk of hypoglycemia.
* **Phenytoin:** Increased phenytoin levels.
## Monitoring
* Renal function (BUN, creatinine).
* Electrolytes (especially potassium).
* Complete blood counts (CBC) with differential, especially with prolonged therapy or in patients with G6PD deficiency.
* Liver function tests (LFTs).
* Signs of hypersensitivity reactions (rash, fever).
## Clinical Pearls
* Administer with adequate fluid intake to prevent crystalluria.
* Sulfonamides can displace bilirubin from albumin, leading to kernicterus in neonates. Avoid in infants < 2 months.
* Photosensitivity can occur; advise patients to use sun protection.
* Consider a test dose in patients with a history of sulfa allergy, although cross-reactivity can still occur.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant guidelines before administering any medication.*
