Drug Interaction Report

Theoretically, coadministration of dapsone with inducers of CYP450 3A4 such as rifamycins, anticonvulsants, barbiturates, and St. John's wort may increase the formation of dapsone hydroxylamine, a metabolite associated with hemolysis. Dose-related hemolysis is the most common adverse event associated with oral dapsone in both patients with or without glucose-6-phosphate dehydrogenase (G6PD) deficiency. While clinical studies have not demonstrated evidence of clinically significant anemia in patients treated with dapsone 5% gel for acne vulgaris, an increased reticulocyte count and a decreased hemoglobin level were noted to be associated in a G6PD-deficient patient. Exposure to dapsone from the recommended topical dose is about 1% of that from a 100 mg oral dose.