There are no definitive clinical practice guidelines regarding the necessity and dosage of trimethoprim–sulfamethoxazole (TMP/SMX) prophylaxis for Pneumocystis jirovecii pneumonia (PJP) in individuals undergoing rituximab therapy. This retrospective study evaluated the effectiveness and safety of various TMP–SMX prophylactic dosing regimens over a 1-year period in 690 patients with non-Hodgkin lymphoma treated with rituximab at a university hospital in Thailand from 2013 to 2022. Out of these patients, 622 (90.1%) received TMP/SMX, with a mean duration of prophylaxis of 265.7 days (SD 85.66). The overall incidence of PJP was 1% (7 patients), which was significantly higher in the non-prophylaxis group (5.8%, 4 patients) compared to the prophylaxis group (0.6%, 3 patients). No cases of PJP occurred among those receiving standard prophylaxis or a single-strength tablet every other day, three times a week. However, instances in the prophylaxis cohort were reported in patients who took two single-strength tablets twice daily, twice a week. Prophylaxis resulted in a significant reduction in the one-year incidence of PJP, with a hazard ratio of 0.105 (95% CI: 0.023–0.469). Mild adverse reactions were noted in 3.05% of patients, all of whom recovered. These findings suggest that TMP/SMX prophylaxis was associated with a lower incidence of PJP and was well tolerated. Future studies should explore optimal dosing strategies while considering patient selection bias and concurrent immunosuppressive therapy.
Charoenrit et al. (2026) studied this question.