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.
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%; 
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.