Keep track of Closely (one)phenobarbital will decrease the level or result of fentanyl transmucosal by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Check Carefully. Coadministration of fentanyl with CYP3A4 inducers could lead on to the lessen in fentanyl plasma concentrations, deficiency of efficacy or, quite possibly, impr