Adverse drug reactions to trimethoprim-sulfamethoxazole in systemic lupus erythematosus

Objectives Trimethoprim-sulfamethoxazole (TMP-SMX), a prophylactic agent against pneumocystis pneumonia (PCP), can cause adverse drug reactions (ADRs), particularly in patients with systemic lupus erythematosus (SLE). However, the risk factors for ADRs remain unclear. Thus, we sought to examine the prevalence of TMP-SMX-related ADRs in patients with SLE and identify specific risk factors for ADR development in these patients. Methods We retrospectively reviewed data from patients with connective tissue disease (CTD) who were administered TMP-SMX as a PCP prophylactic. The prevalence of ADRs was compared between patients with SLE and those with other CTDs. Univariate and multivariate analyses were conducted to identify risk factors for ADRs in patients with SLE. Results Of the 424 patients with CTD included in our study (SLE, n = 162; other CTDs, n = 262), 22 with SLE (13.6%) developed ADRs, and this rate was significantly higher than that observed in patients with non-SLE CTDs (n = 18 [6.9%], p = 0.033). In patients with SLE, univariate analyses revealed direct associations of ADRs with anti-Sm (p < 0.001), anti-RNP (p = 0.02), and anti-Ro/SS-A antibodies (p = 0.042). Multivariate analysis identified a significant association between anti-Sm antibody levels and the development of ADRs (adjusted odds ratio 5.27, 95% confidence interval 1.80-15.40, p = 0.002). Conclusions Patients with SLE who are prophylactically administered TMP-SMX are at high risk of ADRs. Among these patients, those who display a positive anti-Sm antibody should be carefully monitored for ADRs.