The role of trimethoprim/sulfamethoxazole in preventing opportunistic infections in systemic lupus erythematosus patients receiving low-level immunosuppressive treatment: an open-label, randomized, controlled trial

OBJECTIVE: Systemic lupus erythematosus (SLE) patients receiving immunosuppressive therapy are at risk for opportunistic infections (OIs), particularly Pneumocystis pneumonia (PCP). This study aimed to evaluate the effectiveness of trimethoprim/sulfamethoxazole (TMP/SMX) as primary prophylaxis against OIs and its adverse effects in SLE patients receiving low-level immunosuppressive treatment in a real-world setting. METHODS: This open-label randomized controlled trial enrolled SLE patients receiving low-level immunosuppressive treatment at Ramathibodi Hospital between May 2021 and December 2022. Patient demographics and relevant clinical data were collected. Participants were randomized 1:1 to receive TMP/SMX or no prophylaxis, with dose adjustments according to renal function. The incidences of TMP/SMX-sensitive OIs and adverse events were monitored for 12 months post-enrollment. RESULTS: The trial was terminated early due to a high rate of adverse drug reactions (ADRs) associated with TMP/SMX. In total, 138 SLE patients receiving low-level immunosuppressive treatment were enrolled. Most patients (98.4%) were in disease remission. No TMP/SMX-sensitive OIs were observed in either group during the 12-month follow-up period. Among individuals receiving TMP/SMX, 10/70 (14.3%) developed ADRs. Of these 10 patients, eight experienced grade 1 ADRs, and two had grade 3 ADRs; all declined to resume prophylaxis. There were no deaths in the study. CONCLUSIONS: During the 12-month follow-up period, no TMP/SMX-sensitive OIs occurred in SLE patients receiving low-level immunosuppressive therapy, suggesting that primary prophylaxis with TMP/SMX may not significantly benefit this population. The high rate of ADRs observed underscores the need for clinicians to carefully consider the risks and benefits of TMP/SMX prophylaxis in these patients.