Efficacy of once-weekly dapsone dosing for Pneumocystis jirovecii pneumonia prophylaxis post transplantation

Background. Pneumocystis jirovecii pneumonia (PCP) remains a concern after organ transplantation. In 2005, the University of Kentucky (UK) Transplant Center implemented a novel dosing regimen of weekly dapsone as an alternative for patients with contraindications or intolerability to trimethoprim-sulfamethoxazole (TMP-SMZ), which remains the drug of choice. The purpose of this study was to compare the efficacy of weekly dapsone with TMP-SMZ in preventing PCP post transplantation. Methods. A single-center, cohort, retrospective review of kidney and liver transplant patients from January 2005 to December 2012 was conducted. Patients who were identified as dapsone cases were matched in a 1:1 ratio with TMP-SMZ controls based on type of transplant, age, primary diagnosis, and gender. The primary endpoint assessed was the diagnosis of PCP at 6 and 12 months post transplant. Results. A total of 158 patients were included in the study. No documented cases of PCP occurred in either study group at 6 or 12 months (P = 1.0). In dapsone patients 35 (44%) cases of breakthrough infection occurred, compared to 24 (30%) in the TMP-SMZ group (P = 0.07) within 12 months post transplant. In the dapsone group, 52 (65%) patients were hospitalized within 6 months post transplant compared to 36 (46%) patients in the TMP-SMZ group (P = 0.01). Similar results were seen in patients hospitalized within 12 months post transplant; 49% of patients were switched from TMP-SMZ to dapsone owing to renal dysfunction. Conclusion. No documented cases of PCP occurred in either study group. Future studies are warranted to show the efficacy of weekly dapsone dosing compared to other PCP prophylaxis regimens.