Increased clearance w/ enzyme inducers eg, phenytoin, barbiturates, primidone, carbamazepine, rifampicin; oxcarbazepine, topiramate, felbamate, griseofulvin, St. John's wort-containing products. Decreased systemic exposure at steady state w/ rifampicin. Increased or decreased plasma conc w/ HIV/HCV PIs & NNRTIs. May increase plasma levels w/ strong & moderate CYP3A4 inhibitors eg, azole antifungals (eg, itraconazole, voriconazole, fluconazole), verapamil, macrolides (eg, clarithromycin, erythromycin), diltiazem & grapefruit juice. Increased steady state plasma levels w/ ketoconazole & erythromycin. May influence the results of lab tests including biochemical parameters of liver, thyroid, adrenal & renal function, plasma levels of proteins (eg, lipid/lipoprotein fractions, carbohydrate metabolism parameters, & coagulation & fibrinolysis parameters).