Increased clearance of sex hormones. Diminished efficacy w/ barbiturates, bosentan, carbamazepine, phenytoin, primidone, rifampicin, efavirenz, felbamate, griseofulvin, oxcarbazepine, topiramate, rifabutin, St. John's wort (
Hypericum perforatum)-containing herbal products. Increased/decreased plasma conc w/ HIV PIs (eg, ritonavir, nelfinavir), NNRTIs (eg, nevirapine), HCV medicinal products (eg, boceprevir, telaprevir). Increased serum conc w/ strong (eg, ketoconazole, itraconazole, clarithromycin) or moderate (eg, fluconazole, diltiazem, erythromycin) CYP3A4 inhibitors. Increased plasma & tissue conc of ciclosporin. Decreased plasma & tissue conc of lamotrigine.