Single-Center 5-Year Observational Study of Thrice-Weekly Single-Strength Sulfamethoxazole–Trimethoprim as Adequate Prophylaxis for Pneumocystis jirovecii Pneumonia in Patients with Heart Transplants

Background/Objectives: Pneumocystis jirovecii pneumonia is a significant contributor to morbidity and mortality in patients with solid organ transplants. Sulfamethoxazole–trimethoprim prophylaxis has greatly reduced the incidence of this deadly fungal infection. Traditional prophylactic dosing includes single strength (400–80 mg) daily or double strength (800–160 mg) thrice weekly, but is limited by side effects. This study evaluates the efficacy and tolerability of a sulfamethoxazole–trimethoprim single-strength thrice-weekly prophylactic dosing strategy. Methods: This was a single-center, retrospective chart review of 421 patients with 423 total heart transplants at Cedars Sinai Medical Center between July 2016 and June 2020.A total of 361 patients (363 heart transplants) were started on single-strength sulfamethoxazole–trimethoprim thrice weekly for 1 year, based on institutional guidelines. Results: Patients were followed for a median of 3.86 years (range 0.17 to 6.57). Sulfamethoxazole–trimethoprim was started at a median of 7 days (range 0 to 132) for median duration of 11.5 months (range 0.25 to 22). There were no documented Pneumocystis jirovecii pneumonia cases during the study period. At 1 year, 36% of patients had discontinued sulfamethoxazole–trimethoprim. The most common causes for discontinuation were leucopenia (30.8%) and hyperkalemia (2.2%). Conclusions: In our experience, single-strength sulfamethoxazole–trimethoprim thrice weekly for 1 year effectively prevents Pneumocystis jirovecii pneumonia after heart transplant. Further multicenter studies with other patient populations will need to be performed to explore this well-tolerated strategy.