Overview
DESCRIPTION Dapsone-USP, 4,4'-diaminodiphenylsulfone (DDS), is a primary treatment for Dermatitis herpetiformis. It is an antibacterial drug for susceptible cases of leprosy. It is a white, odorless crystalline powder, practically insoluble in water and in-soluble in fixed and vegetable oils. Dapsone is issued on prescription in tablets of 25 and 100 mg for oral use.
Mechanism of Action
CLINICAL PHARMACOLOGY Actions The mechanism of action in Dermatitis herpetiformis has not been established. By the kinetic method in mice, Dapsone is bactericidal as well as bacteriostatic against Mycobacterium leprae. Absorption and Excretion Dapsone, when given orally, is rapidly and almost completely absorbed. About 85 percent of the daily intake is recoverable from the urine mainly in the form of water-soluble metabolites. Excretion of the drug is slow and a constant blood level can be maintained with the usual dosage. Blood Levels Detected a few minutes after ingestion, the drug reaches peak concentration in 4 to 8 hours. Daily administration for at least eight days is necessary to achieve a plateau level. With doses of 200 mg daily, this level averaged 2.3 mcg/ml with a range of 0.
Indications
- INDICATIONS AND USAGE Dermatitis herpetiformis: (D.H.) Leprosy: All forms of leprosy except for cases of proven Dapsone resistance.
Common Doses
- 50 mg
- 300 mg
- 100 mg
- 600 mg
Dosage
DOSAGE AND ADMINISTRATION Dermatitis herpetiformis The dosage should be individually titrated starting in adults with 50 mg daily and correspondingly smaller doses in children. If full control is not achieved within the range of 50 to 300 mg daily, higher doses may be tried. Dosage should be reduced to a minimum maintenance level as soon as possible. In responsive patients there is a prompt reduction in pruritus followed by clearance of skin lesions. There is no effect on the gastrointestinal component of the disease. Dapsone levels are influenced by acetylation rates.
Contraindications
- CONTRAINDICATIONS Hypersensitivity to Dapsone and/or its derivatives.
Side Effects
- ADVERSE REACTIONS In addition to the warnings listed above, the following syndromes and serious reactions have been reported in patients on Dapsone. Hematologic Effects Dose-related hemolysis is the most common adverse effect and is seen in patients with or without G6PD deficiency. Almost all patients demonstrate the inter-related changes of a loss of 1 to 2g of hemoglobin, an increase in the reticulocytes (2 to 12%), a shortened red cell life span and a rise in methemoglobin. G6PD deficient patients have greater responses.
Interactions
- Drug Interactions Rifampin lowers Dapsone levels 7 to 10-fold by accelerating plasma clearance; in leprosy this reduction has not required a change in dosage. Folic acid antagonists such as pyrimethamine may increase the likelihood of hematologic reactions. A modest interaction has been reported for patients receiving 100 mg Dapsone daily in combination with trimethoprim 5 mg/kg q6h. On Day 7, the serum Dapsone levels averaged 2.1 ± 1.0 mcg/mL in comparison to 1.5 ± 0.5 mcg/mL for Dapsone alone. On Day 7, trimethoprim levels averaged 18.4 ± 5.2 mcg/mL in comparison to 12.4 ± 4.