Watch Carefully (one)phenobarbital will minimize the level or outcome of fentanyl transmucosal by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Check Carefully. Coadministration of fentanyl with CYP3A4 inducers could lead to a minimize in fentanyl plasma concentrations, deficiency of efficacy or, maybe, enhancement of the wi