pentobarbital will lower the extent or result of gefitinib by impacting hepatic/intestinal enzyme CYP3A4 metabolism.pentobarbital will decrease the level or influence of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep track of Closely. Coadministration of fentanyl with CYP3A4 inducers may lead to the minimize