Septrin Prophylactic Dose for BSA 1.1
For a patient with BSA 1.1 m², the recommended Septrin (co-trimoxazole) prophylactic dose is 1 tablet (400mg/80mg single-strength) every 12 hours, based on the pediatric dosing guideline of 750 mg/m²/day sulfamethoxazole with 150 mg/m²/day trimethoprim given in equally divided doses twice daily. 1, 2
Dose Calculation
The FDA-approved prophylactic dosing for Pneumocystis carinii pneumonia (PCP) prophylaxis uses body surface area as the primary dosing parameter 1, 2:
- For BSA 1.0-1.06 m²: The guideline specifies 1 tablet every 12 hours 1, 2
- For BSA 0.26-0.53 m²: The guideline specifies ½ tablet every 12 hours 1, 2
Since your patient has BSA 1.1 m², which exceeds 1.06 m², the appropriate dose would be 1 tablet (400mg/80mg) every 12 hours, which provides approximately 727 mg/m²/day sulfamethoxazole and 145 mg/m²/day trimethoprim—within the recommended range of 750 mg/m²/day sulfamethoxazole with 150 mg/m²/day trimethoprim 1, 2.
Alternative Adult Dosing
If this is an adult patient, the standard adult prophylactic dose is simpler 1, 2:
- 1 double-strength tablet (800mg/160mg) once daily for PCP prophylaxis 1, 2
- This adult dosing does not require BSA calculation and is the preferred approach for adults 1, 2
Clinical Context Considerations
For peritoneal dialysis patients with BSA 1.1 m² (which falls between 1.7-2.0 m² range), the BSA-based dosing approach is well-established in nephrology practice 3. However, Septrin dosing specifically uses the FDA-approved BSA tables rather than the peritoneal dialysis BSA categories 1, 2.
For HIV prophylaxis, co-trimoxazole prophylaxis has demonstrated mortality reduction and should be continued regardless of CD4 count in settings with high infectious disease burden 4. The standard adult dose of one double-strength tablet daily is appropriate 4.
Important Caveats
- Not recommended for pediatric patients less than 2 months of age 1, 2
- Renal impairment requires dose adjustment: For creatinine clearance 15-30 mL/min, use half the usual regimen; for creatinine clearance below 15 mL/min, use is not recommended 1, 2
- The total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim when using BSA-based dosing 1, 2
- Monitor for adverse effects: Approximately 25-33% of patients experience adverse effects, though treatment discontinuation is rarely necessary 5