What are the major toxicities of dapsone?
All patients treated with dapsone will have some degree of hemolysis and methemoglobinemia and should be thus supplemented with 1 mg of folate daily. Patients with G6PD deficiency will have severe hemolysis, so all patients should be screened, particularly those of Mediterranean or African descent. The hemolysis is attributable to a metabolite of dapsone causing oxidation of glutathione, which is essential for erythrocyte membrane integrity. G6PD is necessary to produce nicotinamide adenine dinucleotide phosphate, also called NADPH, which is a cofactor for glutathione reductase, which reduces the oxidized glutathione back to an active form.
Other side effects can include leukopenia, hypersensitivity syndrome, liver toxicity, nausea, and peripheral neuropathy (on high doses). Monitoring should include CBC and reticulocyte count every month for 3 months, then every 3 months with renal and liver tests.