Keep an eye on Closely (1)pentobarbital will minimize the level or outcome of fentanyl by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Intently. Coadministration of fentanyl with CYP3A4 inducers may lead to the decrease in fentanyl plasma concentrations, not enough efficacy or, probably, improvement of a withdrawa