A number of medications closely related to the sulfonamides (eg, dapsone) have been used effectively in the long-term treatment of leprosy. The clinical manifestations of both lepromatous and tuberculoid leprosy can often be suppressed by treatment extending over several years. At least 5–30% of Mycobacterium leprae organisms are resistant to dapsone, so initial three-drug treatment with rifampin, dapsone, and clofazimine is advocated. Dapsone, 100 mg daily, is effective therapy for mild to moderate Pneumocystis pneumonia in AIDS when combined with trimethoprim, 15 mg/kg/day in three divided doses. At a dose of 50–100 mg daily or 100 mg two or three times a week, it is effective prophylaxis for P jirovecii infection and, when combined with pyrimethamine, 50 mg per week, also prevents Toxoplasma encephalitis in HIV-infected patients.
ABSORPTION, METABOLISM, & EXCRETION
All sulfones are well absorbed from the intestinal tract, are distributed widely in all tissues, and tend to be retained in skin, muscle, liver, and kidney. Leprous skin retains 10 times more medication than normal skin. Sulfones are excreted into the bile and reabsorbed by the intestine, prolonging therapeutic blood levels. Excretion into the urine is variable, and the medication occurs in urine mostly as a glucuronic acid conjugate.
DOSAGES & ROUTES OF ADMINISTRATION
See the section on Leprosy in Chapter 33-37 for recommendations.
The sulfones may cause any of the side effects listed above for sulfonamides. Considering that sulfones can be cross-reactive with sulfonamides, they should not be used in those patients experiencing significant sulfonamide adverse events. Anorexia, nausea, and vomiting are common. Hemolysis, methemoglobinemia, or agranulocytosis may occur. G6PD status should always be determined prior to initiation of dapsone therapy. If sulfones are not tolerated, clofazimine can be substituted.
KF. Dapsone safety in hematology patients: pathways to optimizing Pneumocystis jirovecii
pneumonia prophylaxis in hematology malignancy and transplant recipients. Transpl Infect Dis. 2018;20:e12968.