Increased conc of anticoagulant, caffeine, benzodiazepine, cyclosporin. Increased OC conc w/ atorvastatin or theophylline. Decreased OC conc w/ barbiturates, carbamazepine, griseofulvin, phenytoin, primidone, rifabutin, rifampin, ritonavir, St. John's wort, troglitazone.