Abstract
Objectives
To investigate long-term prophylactic efficacy, drug retention, and safety of low-dose sulfamethoxazole/trimethoprim (SMX/TMP) prophylaxis against Pneumocystis pneumonia (PCP).
Methods
Adult patients with rheumatic diseases receiving prednisolone ≥0.6 mg/kg/day were randomized into the single-strength group (SS; SMX/TMP 400/80 mg daily), the half-strength group (HS; 200/40 mg daily), and escalation group (ES; starting at 40/8 mg and increased incrementally to 200/40 mg daily) and treated for 24 weeks, then observed for 52 weeks. The primary endpoint, the PCP non-incidence rate (non-IR) at week 24, was reported previously. The secondary endpoints were the PCP non-IR at week 52, treatment discontinuation rate, and adverse events (AEs).
Results
Fifty-eight, 59, and 55 patients in the SS, HS, and ES, respectively, received SMX/TMP. PCP did not develop in any of the patients by week 52. The estimated PCP non-IR in patients receiving SMX/TMP 200/40 mg daily (HS and ES) was 96.8–100%. Throughout the 52-week observation period, the overall discontinuation rate was significantly lower in HS than in SS (22.7% vs 47.2%, p = 0.004). The discontinuation rates due to AEs were significantly lower in HS (19.1%, p = 0.007) and ES (20.3%, p = 0.007) than in SS (41.8%). The IRs of AEs requiring SMX/TMP dose reduction through week 52 differed among the three groups, with a significantly higher IR in SS than in HS or ES (p = 0.007).
Conclusion
SMX/TMP 200/40 mg had a high PCP prevention rate and is superior to SMX/TMP 400/80 mg in terms of drug retention and safety.