Bactrim (Trimethoprim/Sulfamethoxazole) Prophylaxis Dosing
For prophylaxis purposes, the recommended dose of Bactrim is one double-strength tablet (160mg trimethoprim/800mg sulfamethoxazole) daily or one double-strength tablet three times weekly. 1
Prophylaxis Dosing Options
Adults and Adolescents:
- First-line regimen: One double-strength tablet (160mg/800mg) daily 1
- Alternative regimens:
Children:
- Standard dosing: 750 mg/m² sulfamethoxazole with 150 mg/m² trimethoprim daily, divided into two doses 3
- Alternative regimen: Twice daily dosing on two non-consecutive days per week 4
Dosing based on indication:
HIV-Related PCP Prophylaxis:
Immunosuppression from Other Causes:
- One double-strength tablet daily or three times weekly 1
- For children receiving chemotherapy or stem cell transplantation: twice daily on two non-consecutive days per week 4
Special Considerations
Renal Impairment:
- CrCl >30 mL/min: Standard regimen
- CrCl 15-30 mL/min: Half the usual regimen
- CrCl <15 mL/min: Not recommended 3
Tolerability:
- Half-strength dosing (40mg/200mg daily) may be more tolerable than conventional dosing (80mg/400mg daily) in patients with mild renal impairment 5
- For patients who experience non-life-threatening adverse reactions, continuing TMP-SMZ is recommended if clinically feasible 1
- For those who discontinued due to adverse reactions, reintroduction should be strongly considered after the adverse event resolves 1
Monitoring
- Complete blood counts with differential and platelet count should be performed at initiation of prophylaxis and monthly thereafter 6
- Monitor for common adverse effects:
- Rash
- Gastrointestinal disturbances
- Hematologic abnormalities
- Hepatotoxicity
Important Considerations
- When used with methotrexate, be aware of potential drug interactions, especially at higher doses of TMP-SMX 1
- For patients with ANCA-associated vasculitis, TMP-SMX is not recommended as the sole agent for remission maintenance but may be beneficial for patients with sinonasal involvement 1
- For patients who cannot tolerate TMP-SMX, alternative prophylactic agents include dapsone, atovaquone, or aerosolized pentamidine 1
By selecting the appropriate prophylactic regimen based on the patient's clinical condition and renal function, Bactrim provides effective prophylaxis against Pneumocystis jirovecii pneumonia and other opportunistic infections in immunocompromised patients.