Keep an eye on Carefully (one)pentobarbital will lessen the extent or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep an eye on Intently. Coadministration of fentanyl with CYP3A4 inducers may lead to the reduce in fentanyl plasma concentrations, not enough efficacy or, perhaps, enhancement of the wit