Trimethoprim-sulfamethoxazole (TMP/SMX) is effective as prophylaxis against many infections in immunocompromised patients. However, it is not commonly prescribed for patients with systemic lupus erythematous (SLE) due to the risk of adverse reactions (ADRs). An upfront graded administration protocol for TMP/SMX was adopted, and its safety and efficacy were assessed.

Data from 59 patients with SLE patients who received prophylactic TMP/SMX were retrospectively analyzed. The incidence and risk factors for ADRs in patients who received TMP/SMX before and after the introduction of graded administration were assessed.

The incidence of ADRs was 41.9% in the non-graded administration group, vs. 10.7% in the graded administration group (p = 0.009). The rate of high fever, liver function test (LFT) abnormality, shortness of breath, and hospitalization were reduced in upfront graded administration group. In addition, a higher rate of anti-Ro/SS-A positivity was found in patients experienced ADRs (46.2% in reactors vs. 5.6% in non-reactors; p = 0.012) in the non-graded administration group.

Upfront graded administration of TMP/SMX reduces the incidence and severity of ADRs in SLE patients. The high incidence of TMP/SMX ADRs in SLE patients was also confirmed, especially when anti-Ro/SS-A antibody is present.