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## Septran (Co-trimoxazole)
### Overview
Septran is a combination antibiotic containing sulfamethoxazole and trimethoprim. It is a broad-spectrum agent effective against many Gram-positive and Gram-negative bacteria.
### Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Acute otitis media
* Acute exacerbations of chronic bronchitis
* Shigellosis
### Adult Dosing
* **UTIs:** 160 mg trimethoprim / 800 mg sulfamethoxazole (1 DS tablet) every 12 hours for 3-7 days.
* **PJP Treatment:** 15-20 mg/kg/day trimethoprim component, divided into 4 doses every 6 hours for 14-21 days.
* **PJP Prophylaxis:** 1 DS tablet daily or 1 DS tablet three times weekly.
* **Shigellosis:** 160 mg trimethoprim / 800 mg sulfamethoxazole (1 DS tablet) every 12 hours for 5 days.
* *Specific dosing for other indications may vary based on local protocols.*
### Pediatric Dosing
* **UTIs (>= 2 months):** 8 mg/kg/day trimethoprim component, divided into 2 doses every 12 hours. Dosing for sulfamethoxazole is typically 40 mg/kg/day divided into 2 doses.
* **PJP Treatment (>= 2 months):** 15-20 mg/kg/day trimethoprim component, divided into 4 doses every 6 hours for 14-21 days.
* **PJP Prophylaxis (>= 2 months):** 5 mg/kg/day trimethoprim component, divided into 2 doses daily, or 10 mg/kg/day trimethoprim component given on alternate days. *This is often dosed as 1 DS tablet daily or 1 DS tablet three times weekly for children over 12 years or weighing >40 kg, adjusted by weight for younger children.*
* *Maximum pediatric dose for trimethoprim is typically 16 mg/kg/day. Consult specific guidelines for precise pediatric dosing.*
### Dose Adjustments
* **Renal Impairment:**
* CrCl > 30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Give half the usual dose.
* CrCl < 15 mL/min: Avoid use or give one-quarter the usual dose.
### Contraindications
* Known hypersensitivity to trimethoprim or sulfonamides.
* Documented megaloblastic anemia due to folate deficiency.
* Infants < 2 months of age (due to risk of kernicterus).
* Severe renal or hepatic insufficiency when pharmacokinetic monitoring is not feasible.
* Pregnancy at term and lactation (due to risk of kernicterus in neonates).
### Adverse Effects
* **Common:** Nausea, vomiting, rash (can be severe, including Stevens-Johnson syndrome and toxic epidermal necrolysis), pruritus, hyperkalemia.
* **Less Common:** Diarrhea, headache, dizziness, blood dyscrasias (leukopenia, thrombocytopenia, aplastic anemia), hepatic injury, crystalluria (ensure adequate fluid intake).
* **Sulfonamide specific:** Photosensitivity, serum sickness-like reactions.
### Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely and adjust warfarin dose.
* **Methotrexate:** Increased risk of methotrexate toxicity. Avoid concurrent use or monitor methotrexate levels and folate status.
* **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia.
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Digoxin:** May increase digoxin levels. Monitor digoxin levels.
* **Cyclosporine:** Increased cyclosporine levels and nephrotoxicity.
* **Oral hypoglycemics:** May potentiate hypoglycemic effects. Monitor blood glucose.
* **Rifampin:** May increase the clearance of sulfamethoxazole.
* **Dofetilide:** Contraindicated due to increased risk of ventricular arrhythmias.
### Monitoring
* Renal function (BUN, creatinine).
* Electrolytes, especially potassium.
* Complete blood counts (CBC) with differential, particularly with prolonged therapy or in immunocompromised patients.
* Liver function tests.
* Signs of hypersensitivity reactions.
* For patients on warfarin, INR.
### Clinical Pearls
* Advise patients to drink plenty of fluids to prevent crystalluria.
* Rash should be reported immediately as it can be a sign of a severe reaction.
* Sun protection is recommended due to photosensitivity risk.
* Use with caution in patients with G6PD deficiency.
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*Please verify this information with the most current prescribing information and relevant clinical guidelines.*
