Bactrim Dosage for PJP Prophylaxis
For PJP prophylaxis, the standard regimen is one double-strength tablet (800 mg sulfamethoxazole/160 mg trimethoprim) three times weekly, typically on Monday-Wednesday-Friday, or alternatively one double-strength tablet daily. 1, 2
Standard Prophylaxis Dosing Options
The FDA-approved and guideline-recommended regimens include:
- One double-strength tablet (DS: 800/160 mg) three times weekly - This is the most commonly used regimen for prophylaxis 3, 1, 2
- One double-strength tablet daily - Alternative daily dosing option 1, 2
- For pediatric patients: 750 mg/m²/day sulfamethoxazole with 150 mg/m²/day trimethoprim given in equally divided doses twice daily on 3 consecutive days per week, not exceeding 1600 mg sulfamethoxazole and 320 mg trimethoprim total daily 2
Duration of Prophylaxis by Population
Solid organ transplant recipients (including liver transplant): Continue for 6-12 months post-transplant 3, 4
HIV patients: Continue until CD4+ count >200 cells/μL for at least 3 months 1, 5
Patients on chronic immunosuppression: Continue while receiving ≥20 mg prednisone daily (or equivalent) for ≥4 weeks, or while on triple immunosuppressive therapy 4, 5
Hematologic malignancy patients: Duration varies by specific condition - ALL patients require prophylaxis throughout anti-leukemic therapy, allogeneic stem cell transplant recipients for at least 6 months and while on immunosuppressive therapy 4
Alternative Regimens for Sulfa-Allergic Patients
If TMP-SMX cannot be used due to allergy or intolerance:
- Dapsone 100 mg daily (requires G6PD testing before initiation) 1, 5
- Atovaquone 1500 mg daily 1, 5
- Aerosolized pentamidine 300 mg monthly via Respirgard II nebulizer 5
Critical Pitfalls to Avoid
Do not confuse prophylaxis dosing with treatment dosing - Treatment requires much higher doses (15-20 mg/kg/day of trimethoprim component divided every 6-8 hours), while prophylaxis uses the lower three-times-weekly or daily single-tablet regimen 4, 2
Check for drug interactions - TMP-SMX combined with methotrexate increases risk of severe cytopenia 4
Always check G6PD levels before using dapsone or primaquine alternatives to prevent life-threatening hemolysis 4, 5
Monitor for adverse effects including rash, cytopenias, and transaminase elevations, particularly with daily dosing 1