Observe Intently (one)phenobarbital will minimize the extent or result of fentanyl transmucosal by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Observe Carefully. Coadministration of fentanyl with CYP3A4 inducers could lead on into a minimize in fentanyl plasma concentrations, not enough efficacy or, potentially, improvem