Keep an eye on Carefully (1)oxcarbazepine will lower the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Intently. Coadministration of fentanyl with CYP3A4 inducers could lead on to the minimize in fentanyl plasma concentrations, insufficient efficacy or, possibly, improvement of the with