The azole antifungals are potent
enzyme inhibitors, but they do not all affect the same isoenzymes. This explains their differing interaction profiles.
Fluconazole is a potent inhibitor of CYP2C9 and CYP2C19, and generally only
inhibits CYP3A4 at high doses (greater than 200 mg daily). Interactions are less likely with single doses used for genital candidiasis than with longer term use.
Itraconazole and its major metabolite, hydroxy-itraconazole, are potent inhibitors
of CYP3A4.
Ketoconazole is a potent inhibitor of CYP3A4.
Miconazole is a potent inhibitor of CYP2C9.
Posaconazole is an inhibitor of CYP3A4.
Voriconazole is an inhibitor of CYP2C9, CYP2C19 and CYP3A4. A number of other azole antifungals are only used topically in the form of skin creams or intravaginal preparations, and are not usually been associated with drug interactions, presumably because their systemic absorption is so low. Fluconazole, ketoconazole and voriconazole have been associated with prolongation of the QT interval, although generally not to a clinically relevant extent. However, they may also raise the levels of other drugs that prolong the QT interval, and these combinations are often contraindicated.