Increased risk of ALT elevations w/ ombitasvir/paritaprevir/ritonavir & dasabuvir, w/or w/o ribavirin. Decreased ethinylestradiol serum conc w/ drugs reducing GI transit time & absorption, rifampicin, rifabutin, barbiturates, primidone, phenylbutazone, phenytoin, dexamethasone, griseofulvin, topiramate, some PIs, modafinil, St. John's wort, ritonavir. Increased ethinylestradiol serum conc w/ atorvastatin, ascorbic acid, paracetamol, indinavir, fluconazole, troleandomycin. Increased plasma & tissue conc w/ cyclosporine, theophylline, corticosteroids. Decreased plasma & tissue conc w/ lamotrigine. Increased risk of galactorrhea w/ flunarizine. Increased risk of intrahepatic cholestasis w/ troleandomycin. Reports of pregnancy w/ certain antibiotics eg, ampicillin, other penicillin & tetracyclines. Interference w/ LFTs, thyroid, adrenal & renal function, other lab & diagnostic tests.