Dosage of TMP-SMX for HIV-Related PCP Treatment
For treatment of documented Pneumocystis jirovecii pneumonia (PCP) in HIV patients, the recommended dosage is 75-100 mg/kg/day of sulfamethoxazole (SMX) and 15-20 mg/kg/day of trimethoprim (TMP) given in equally divided doses every 6 hours for 14-21 days. 1, 2
Treatment Dosing Details
- The FDA-approved dosage for treatment of documented PCP in adults and children is 75-100 mg/kg/day of SMX and 15-20 mg/kg/day of TMP divided into equal doses given every 6 hours for 14-21 days 1
- This treatment regimen should be continued for the full course to ensure complete eradication of the infection 3
- For the upper limit dose (100 mg/kg SMX and 20 mg/kg TMP per 24 hours), dosing is based on weight 1, 2
- For the lower limit dose (75 mg/kg SMX and 15 mg/kg TMP per 24 hours), administer 75% of the upper limit dose 1
Weight-Based Dosing Guide (for upper limit dose)
| Weight (kg) | Dose (every 6 hours) |
|---|---|
| 8-16 | 1 tablet |
| 24 | 1½ tablets |
| 32 | 2 tablets or 1 DS |
| 40 | 2½ tablets |
| 48 | 3 tablets or 1½ DS |
| 64 | 4 tablets or 2 DS |
| 80 | 5 tablets or 2½ DS |
DS = Double Strength tablet (800 mg SMX/160 mg TMP) 1
Recent Evidence on Lower Dosing
- Recent research suggests that lower doses of TMP-SMX (approximately TMP 10 mg/kg/day and SMX 50 mg/kg/day) may be equally efficacious with fewer adverse effects 4, 5
- A 2020 meta-analysis found no significant difference in mortality between conventional and low-dose TMP-SMX regimens, but showed an 18% absolute risk reduction in grade ≥3 adverse events with lower doses 5
- However, the FDA-approved dosing remains the standard of care, particularly for severe cases 1
Special Considerations
- For patients with impaired renal function (creatinine clearance 15-30 mL/min), reduce the dose by 50% 1
- TMP-SMX is contraindicated in patients with creatinine clearance below 15 mL/min 1
- Common adverse effects include rash, neutropenia, thrombocytopenia, and elevated liver enzymes 6
- If severe adverse reactions occur (anaphylaxis, Stevens-Johnson syndrome), the drug should be permanently discontinued 3
- For milder reactions, temporary discontinuation with rechallenge after 2 weeks may be attempted 3
Alternative Regimens
- For patients who cannot tolerate TMP-SMX, alternative options include:
Monitoring During Treatment
- Complete blood counts with differential and platelet counts should be monitored regularly 3
- Renal function and electrolytes should be monitored, particularly in patients with underlying renal impairment 3
- Clinical response should be assessed within 5-7 days; if no improvement is seen, consider alternative therapy 3