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# Septran (Co-Trimoxazole)
## Overview
Co-trimoxazole is a combination antibiotic of trimethoprim and sulfamethoxazole.
## Primary Indications
* **Urinary Tract Infections (UTIs):** Uncomplicated and complicated.
* **Pneumocystis jirovecii pneumonia (PJP) Prophylaxis and Treatment:** In immunocompromised patients.
* **Shigellosis.**
* **Acute exacerbations of chronic bronchitis.**
* **Otitis media.**
## Adult Dosing
Dosing is typically expressed as the total daily dose of co-trimoxazole, which refers to the combined amount of trimethoprim and sulfamethoxazole. Tablets are often formulated as single-strength (80 mg trimethoprim/400 mg sulfamethoxazole) or double-strength (160 mg trimethoprim/800 mg sulfamethoxazole).
* **Uncomplicated UTIs:** 1 double-strength (DS) tablet (160 mg trimethoprim/800 mg sulfamethoxazole) every 12 hours for 3-7 days.
* **PJP Treatment:** 15-20 mg/kg/day trimethoprim component, divided into 3-4 doses, for 14-21 days. For PJP prophylaxis, typical dose is 1 DS tablet daily.
* **Shigellosis:** 1 DS tablet every 12 hours for 5 days.
* **Acute exacerbations of chronic bronchitis:** 1 DS tablet every 12 hours for 7-14 days.
* **Otitis media:** 8-10 mg/kg/day trimethoprim component, divided into 2 doses, for 10 days.
## Pediatric Dosing
Dosing is based on the trimethoprim component.
* **UTIs:** 8 mg/kg/day of trimethoprim component, divided into two doses, for 7 days.
* **PJP Treatment:** 15-20 mg/kg/day of trimethoprim component, divided into 3-4 doses, for 14-21 days.
* **PJP Prophylaxis:** 5 mg/kg/day of trimethoprim component, divided into two doses, given on 3 consecutive days per week.
* **Otitis media:** 8-10 mg/kg/day of trimethoprim component, divided into 2 doses, for 10 days.
## Dose Adjustments
* **Renal Impairment:** Dose adjustment is necessary based on creatinine clearance (CrCl). If CrCl is 15-30 mL/min, administer 50% of the usual dose. If CrCl < 15 mL/min, co-trimoxazole is generally not recommended.
## Contraindications
* Known hypersensitivity to trimethoprim or sulfamethoxazole.
* History of drug-induced thrombocytopenia with sulfonamides or trimethoprim.
* Marked anemia, megaloblastic anemia due to folate deficiency, or history of folate deficiency.
* Severe renal insufficiency where pharmacokinetic monitoring is not feasible.
* Severe hepatic insufficiency.
* Premature infants and full-term infants during the first 2 months of life (risk of kernicterus).
* Documented Porphyria.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, rash.
* **Serious:**
* Hypersensitivity reactions (including Stevens-Johnson syndrome, toxic epidermal necrolysis, anaphylaxis).
* Hematologic abnormalities (leukopenia, thrombocytopenia, hemolytic anemia, megaloblastic anemia).
* Hyperkalemia.
* Renal impairment, interstitial nephritis.
* Hepatotoxicity.
* Photosensitivity.
## Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely.
* **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia.
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Methotrexate:** Increased risk of methotrexate toxicity.
* **Sulfonylureas:** Increased risk of hypoglycemia.
* **Digoxin:** Increased digoxin levels.
* **Tricyclic Antidepressants (TCAs):** Increased risk of bone marrow suppression.
* **Rifampin:** May increase or decrease co-trimoxazole levels; co-trimoxazole may decrease rifampin levels.
## Monitoring
* Renal function (serum creatinine, CrCl).
* Complete blood counts (CBC) with differential and platelet count, especially during prolonged therapy or in patients with G6PD deficiency.
* Electrolytes, particularly potassium.
* Liver function tests.
* For patients on warfarin, monitor INR closely.
## Clinical Pearls
* Co-trimoxazole should be administered with adequate fluid intake to prevent crystalluria.
* Monitor for signs of hypersensitivity reactions and discontinue immediately if they occur.
* Use with caution in patients with G6PD deficiency due to risk of hemolytic anemia.
* When treating UTIs, ensure adequate hydration.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and local protocols for definitive guidance.*
