AZOLES AND DARIFENACIN - ITRACONAZOLE AND KETOCONAZOLE

Ketoconazole markedly increases the AUC of darifenacin by up to 10-fold. Itraconazole is predicted to interact similarly.
The UK manufacturers contraindicate concurrent use with potent CYP3A4 inhibitors whereas the US manufacturers recommend that the daily dose of darifenacin is limited to 7.5 mg daily. It may be prudent to assess adverse effects in these patients, and withdraw the drug if it is not tolerated.