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.

Administration with food may delay the absorption of modafinil (the racemate) and armodafinil (the R-enantiomer) without significantly affecting their overall bioavailability. According to the product labeling, modafinil's absorption may be delayed by approximately one hour if taken with food. Similarly, the time to reach peak plasma concentration (Tmax) of armodafinil may be delayed by approximately 2 to 4 hours in the fed state.