- Concurrent treatment with any medications or substances that are potent inhibitors or inducers of CYP3A4, hepatic enzyme inducing antiepileptic drugs (EIAEDs),or other drugs known to affect the metabolism of modafinil. Examples include but are not limited to itraconazole, ketoconazole, doxycycline, rifampin, St. John's wort, phenytoin, phenobarbital, diazepam, tricyclic antidepressants.