Check Closely (1)phenobarbital will minimize the level or result of fentanyl transmucosal by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep an eye on Carefully. Coadministration of fentanyl with CYP3A4 inducers could lead to some reduce in fentanyl plasma concentrations, insufficient efficacy or, possibly, progress of