A retrospective analysis of 122 immune thrombocytopenia patients treated with dapsone: Efficacy, safety and factors associated with treatment response

The optimum second‐line treatment or best sequence of treatments for immune thrombocytopenia (ITP) are yet to be determined. Our institution has accumulated extensive experience regarding the use of dapsone as second‐line therapy for ITP. We aimed to assess the efficacy rate and safety of dapsone treatment in ITP patients. Here we report our experience in a retrospective study, including 122 patients, with a median treatment duration with dapsone of 6 months and a median follow‐up period of 3.4 years. The overall response rate in this cohort was 66%, including 24% of complete responses. Among responders, in 24% a relapse occurred while on treatment. Therefore, a sustained response was observed in 51% of patients. Interestingly, 81% of the responders maintained the response after the interruption of treatment, for a median time of 26 months. Side effects were reported in 16% of the patients in this cohort and treatment was interrupted due to side effects in 11% of patients. The main cause in these cases was hemolytic anemia and methemoglobinemia. Reductions in hemoglobin levels during the use of dapsone were seen in 94% of the patients. Responders presented significantly greater reductions in their hemoglobin levels than nonresponders did: median hemoglobin drop of 1.9 g/dl vs. 1.2 g/dl (p =.004). Our findings suggest that dapsone has adequate efficacy and is well tolerated. Although the mechanism of action is still unclear, our observation that the degree in the drop of hemoglobin is greater in responders suggest a possible role of the blockage of the reticuloendothelial system in the therapeutic effect of the drug.