Dapsone safety in haematology patients: pathways to optimising Pneumocystis jirovecii pneumonia prophylaxis in haematology malignancy and transplant recipients.

Abstract

Dapsone may be used for Pneumocystis jirovecii pneumonia (PJP) prophylaxis in haematology patients receiving immunosuppressive therapy or after hematopoietic stem cell transplant (HSCT) in the setting of trimethoprim-sulfamethoxazole (TMP-SMX) adverse drug reaction (ADR) history. Dapsone-induced haematological toxicities such as oxidative haemolysis may limit use in these patients and modern assessments of dapsone allergy cross-reactivity in non-HIV patients with a sulphonamide allergy are largely absent. The aim of this single-centre, retrospective study was to describe dapsone usage in haematology patients requiring PJP prophylaxis, including HSCT recipients, over a 12-month period in terms of indications, incidence of dapsone-attributed oxidative haemolysis, and immune cross-reactivity in those previously labelled with a sulphonamide allergy, as well as describing potential opportunities for first-line TMP-SMX PJP prophylaxis reintroduction. Out of 24 patients meeting the study inclusion criteria, 12 (50%) were receiving dapsone PJP prophylaxis post-HSCT. No cases of breakthrough PJP infection were noted. Sixteen patients (67%) were initiated on dapsone to avoid the perceived risk of further myelosuppression with TMP-SMX and 5 patients (21%) due to prior delayed immune-mediated allergy to TMP-SMX. None experienced rash with dapsone therapy. Six patients (25%) were successfully rechallenged on TMP-SMX, including one patient with prior TMP-SMX-associated rash. Four (17%) patients had confirmed oxidative haemolysis, all resulting in dapsone cessation. Dapsone PJP prophylaxis in haematology patients was effective and safe, with non-life threatening dapsone-related haemolysis noted in a small number. An absence of sulphonamide allergy cross-reactivity was noted, suggesting greater TMP-SMX rechallenges or desensitisation could be considered in those receiving dapsone. This article is protected by copyright. All rights reserved.