- Any treatment known to induce CYP isoenzymes (e.g., phenobarbital, phenytoin, carbamazepine, rifampicin, St John's Wort) or to strongly inhibit CYP3A4 activities (e.g., ketoconazole, itraconazole, macrolides, antiprotease agents, etc) is not allowed within 2 weeks before or during the test period of the pharmacokinetic sampling