pentobarbital will decrease the extent or result of gefitinib by influencing hepatic/intestinal enzyme CYP3A4 metabolism.pentobarbital will lessen the extent or result of fentanyl by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep an eye on Carefully. Coadministration of fentanyl with CYP3A4 inducers could lead into a les