(1998; 28 pages)
Group: antileprosy agent
Tablet: 25 mg, 50 mg, 100 mg
A sulfone that remains of prime importance in the treatment of leprosy. Dapsone is both bacteriostatic and weakly bactericidal against M. leprae, the minimum inhibitory concentration for fully sensitive organisms being approximately 0.003 micrograms/ml. However, resistant strains can develop de novo during prolonged treatment with dapsone alone, and their incidence is increasing in previously untreated patients. In some areas the prevalence of primary resistance is currently estimated to be as high as 40%.
After absorption from the gastrointestinal tract, dapsone is distributed widely in body tissues and it is subsequently retained selectively in skin, muscle, liver and kidneys. It is partially acetylated or conjugated in the liver and ultimately excreted in the urine as metabolites. A dose of 100 mg produces a peak serum concentration of approximately 2 micrograms/ml, which declines with a half-life of 1-2 days.
Uses: Paucibacillary and multibacillary leprosy in combination with other antileprosy drugs.
Paucibacillary leprosy (in combination with rifampicin)
Adults: 100 mg daily for 6 months.
Children (10-14 years): 50 mg daily for 6 months
Children, less than 10 years: Adjust the dose. For example, dapsone, 25 mg daily for 6 months
Multibacillary leprosy (in combination with rifampicin and clofazimine)
Adults: 100 mg daily for 12 months
Children (10-14 years): 50 mg daily for 12 months
Children, less than 10 years: Adjust the dose. For example, dapsone, 25 mg daily for 12 months
Contraindications: Known hypersensitivity to sulfones; severe anaemia.
Precautions: Pre-existing severe anaemia should be treated before dapsone therapy is started. Dapsone can induce haemolysis of varying degree, particularly in patients with glucose-6-phosphate dehydrogenase deficiency, and dose-dependent methaemoglobinaemia may supervene during the second week treatment. The clinical response and blood count must therefore be closely monitored in susceptible patients during the first weeks of treatment. Dapsone therapy should not be discontinued if exacerbations occur.
Adverse effects: Dapsone is generally well tolerated at recommended dosages, but symptoms of gastrointestinal irritation occasionally occur. Other less common reactions include headache, nervousness and insomnia.
Blurred vision, paraesthesia, reversible neuropathy, drug fever, skin rashes, and psychoses have also been reported. Hepatitis, Herxheimer reactions and agranulocytosis may rarely occur.
Drug interactions: Concurrent administration of clofazimine to leprosy patients receiving rifampicin with dapsone may decrease the rate of absorption of rifampicin and increase the time to peak plasma level.