Itraconazole and hydroxyitraconazole serum concentrations are reduced more than tenfold by phenytoin*

Abstract

The striking decrease in itraconazole concentrations with phenytoin is due to induction of metabolism combined with a reduction in the degree of saturable metabolism normally exhibited by itraconazole at this dose. The magnitude of interaction likely accounts for reports of therapeutic failures in patients with fungal infections who are receiving both itraconazole and phenytoin.