Watch Carefully (one)oxcarbazepine will decrease the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep an eye on Intently. Coadministration of fentanyl with CYP3A4 inducers could lead into a minimize in fentanyl plasma concentrations, lack of efficacy or, possibly, progress of the withdrawal s