- Current use or anticipated need for drugs that are known strong or moderate CYP3A4 inducers including their administration within 2 weeks prior to the first study treatment (ie, phenobarbital, rifampin, phenytoin, carbamazepine, rifabutin, rifapentin, clevidipine, St. John's Wort). For participants in the dose escalation portion, no CYP3A4 inducers should be administered during the first 21 days of the study, regardless of strength.