Increased clearance of sex hormones w/ phenytoin, barbiturates, primidone, carbamazepine, rifampicin, & possibly oxcarbazepine, topiramate, felbamate, griseofulvin, & products containing St. John's wort (Hypericum perforatum
). Decreased steady state conc & systemic exposure w/ rifampicin. Increased or decreased plasma conc of progestin w/ HIV PIs, NNRTIs & HCV inhibitors. Increased plasma conc w/ strong (eg, ketoconazole) & moderate (eg, erythromycin) CYP3A4 inhibitors.