Can topically used econazole interact with warfarin?/nA 70-year-old man is treated with warfarin be

Fråga: Can topically used econazole interact with warfarin? A 70-year-old man is treated with warfarin because of an earlier TIA. His PT-value (protrombin time) has been stable, around 20. After treatment with econazole cream due to inguinal dermatomucosis the PT-value is 9.

Sammanfattning: We have found no reports concerning interactions between econazole and warfarin in the literature. Theoretically, topical econazole may inhibit warfarin metabolism, as some absorption occurs and as this effect has been shown by similar substances when administered orally.

Svar: We have found no reports concerning a possible interaction between econazole and warfarin in the literature.

Between one and four per cent of topically applied econazole is absorbed, the greater amount with damaged skin and occlusive application. In animal studies systemically administered econazole is extensively metabolized (1). The metabolic pathways are not defined for econazole. A similar substance, micanozole, is metabolised by the same enzyme as warfarin (CYP 3A4). Several other antimucotics have been shown to inhibit the metabolism of warfarin, thus increasing the anti-coagulative effect.

We recommend that this case be reported to the regional center of SADRAC (the Swedish Adverse Drug Reactions Advisory Committee), especially if the PT-value increases again when the econazole treatment is discontinued.