The efficacy and safety of reduced-dose sulfamethoxazole-trimethoprim for chemoprophylaxis of Pneumocystis pneumonia in patients with rheumatic diseases.

Objectives: Pneumocystis pneumonia (PCP) is a life-threatening opportunistic infection. Sulfamethoxazole-trimethoprim (SMX/TMP) is the first-line drug for PCP prophylaxis. However, adverse events (AEs) force clinicians to alter or reduce the drug dosage.
Methods: We retrospectively reviewed all patients with rheumatic diseases who received SMX/TMP for prophylaxis and glucocorticoid therapy between April 2004 and March 2018. The rates of AEs, SMX/TMP discontinuation, and incidence of PCP were analyzed. Patients were divided into the conventional group and the dose-reduction group.
Results: One hundred forty-five patients and 75 patients were included in the conventional group and the dose-reduction group, respectively. Compared to the dose-reduction group, the conventional group had a significantly high frequency of AEs (10.7% vs. 24.1%; p  = .017); however, the rate of discontinuing SMX/TMP was not significantly different (8.0% vs. 14.5%; p  = .165). Thirteen conventional group patients required a reduced SMX/TMP dose because of AEs; no patient developed PCP. The conventional SMX/TMP dose and renal dysfunction were associated with AEs in multivariate analysis.
Conclusion: Patients who received a reduced SMX/TMP dose did not have PCP and had a lower frequency of AEs. A reduction in SMX/TMP for PCP prophylaxis is effective and safe in patients with rheumatic disease.