Frågedatum: 1996-02-09
RELIS database 1996; id.nr. 12133, DRUGLINE
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Is dapsone (avlosulfon) contraindicated in patients with liver damage? Are there any interactions b



Fråga: Is dapsone (avlosulfon) contraindicated in patients with liver damage? Are there any interactions between dapsone and metoprolol or clomipramine? Background: A 47-year-old patient is suffering from dermatitis herpetiformis and dapsone therapy is considered. The patient has elevated gamma-GT levels (probably due to excessive ethanol consumption) and concomitant drug therapy (see above). Because the drug is not on the Swedish market, such information is difficult to obtain.

Sammanfattning: Dapsone is not contraindicated in patients with liver damage but careful follow up is suggested. There are no known interactions between dapsone and metoprolol or clomipramine.

Svar: The antileprotic dapsone (avlosulfon) is not registered in Sweden but is relatively widely used in the treatment of dermatitis herpetiformis. As a sulfone, it is chemically related to sulfonamides. Liver damage is a rare side effect of dapsone therapy. The mechanism is probably immunoallergic and the clinical picture is usually characterized by both hepatocellular and cholestatic features (1). Previous liver damage is not considered as a contraindication for dapsone therapy but according to Meyler´s Encyclopedia, previous liver damage may predispose to hepatic or even other side effects (2,3). A Medline search did not provide any additional information on this matter.

No data or documentation was found about possible interactions between dapsone and metoprolol or clomipramine (4,5). Dapsone is extensively metabolized, both by acetylation and hydroxylation. The N-oxidation occurs most probably via a different P450 isoenzyme system (CYP3A4) than either metoprolol or clomipramine metabolism (CYP2D6). The rate of acetylation shows a genetically determined bimodal distribution, and patients can be divided into slow and fast acetylators. Hematologic side effects (hemolytic anemia, methemoglobinemia) may be more common among slow acetylators (6).

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