18. Use of any enzyme-modifying drugs, including strong inhibitors of cytochrome P450 (CYP) enzymes (e.g. cimetidine, fluoxetine, quinidine, erythromycin, ciprofloxacin, fluconazole, ketoconazole, diltiazem, or HIV antivirals) and strong inducers of CYP enzymes (e.g. glucocorticoids, St. John´s Wort, or rifampicin) in the previous 30 days before first drug administration [barbiturates, carbamazepine, and phenytoin are allowed since these are common AEDs].