Dapsone is an antibacterial drug used to treat leprosy, dermatitis herpetiformis, and other conditions. It works by inhibiting bacterial synthesis of dihydrofolic acid. Common side effects include nausea, headache, and rash. Severe side effects include methemoglobinemia and blood disorders. Dapsone is generally taken once daily but the dosage varies depending on the condition being treated and patient age. It can interact with other medications in ways that affect absorption or increase the risk of side effects.