Since then it has been used to treat leprosy, relapsing polychondritis, prophylaxis of malaria, inflammatory bowel disorders, leishmaniasis, Pneumocystis carinii pneumonia, rheumatic connective tissue disorders, and brown recluse spider bites. This action is not completely understood, though it appears similar to the actions of other sulphones. The anti-inflammatory effects of dapsone seem to be related to the presence of a large number of neutrophils in the affected tissue.
Dapsone interferes with neutrophil infiltration and also suppresses neutrophil adherence.
Peak plasma concentrations are achieved within 2-6 hours. Enterohepatic circulation accounts for appreciable levels in the tissues for 3 weeks after therapy is discontinued. The degree to which dapsone is acetylated is genetically determined. Previous studies have found that dapsone's acetylated metabolites are nontoxic and the hydroxylamine metabolite is responsible for the hematological effects. Dapsone is indicated for the treatment of dermatitis herpetiformis in doses of 50-300 mg per day.