A number of drugs 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 combined treatment with rifampin is advocated. Dapsone, 100 mg daily, is effective therapy for mild to moderate Pneumocystis pneumonia in AIDS when combined with trimethoprim, 20 mg/kg/d in four divided doses. At a dose of 50–100 mg daily or 100 mg two or three times a week, it is effective prophylaxis for Pneumocystis jiroveci (formerly Pneumocystis carinii) 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 contains ten times more drug 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 drug occurs in urine mostly as a glucuronic acid conjugate.

Dosages & Routes of Administration

See Leprosy, in Chapter 33: Bacterial & Chlamydial Infections, for recommendations.

Adverse Effects

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.