Keep track of Closely (1)phenobarbital will reduce the extent or effect of fentanyl transmucosal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Check Carefully. Coadministration of fentanyl with CYP3A4 inducers could lead to your decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of the … Read More