Decreased efficacy w/ CYP3A4 inducers eg, barbiturates, phenytoin, fosphenytoin, carbamazepine, oxcarbazepine, St. John's wort, rifampicin, rifabutin, griseofulvin, efavirenz, nevirapine. Increased C
max & AUC w/ potent & moderate CYP3A4 inhibitor. Reduced plasma conc w/ ritonavir. Lowered mean C
max, delayed T
max & higher mean AUC w/ PPIs. Reduced contraceptive action of combined hormonal contraceptives & progesterone-only contraception. Not recommended w/ levonorgestrel-containing emergency contraceptive.