pentobarbital will reduce the extent or influence of imatinib by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Small/Significance Unfamiliar.pentobarbital will reduce the extent or outcome of fentanyl by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Intently. Coadministration of fentanyl with CYP3A4 inducers