- Has taken/received the following inducers of CYP3A4 within fourteen (14) days prior to the first dose of study medication: glucocorticoids (dexamethasone or dexamethasone equivalent dose > 1.5mg/day (see chart in Section 7.2 for conversion), anticonvulsants (phenytoin, carbamazepine, phenobarbital), efavirenz, nevirapine, antibiotics (rifampin (rifampicin), rifabutin, rifapentine), St. John's Wort and modafinil.