Keep an eye on Intently (one)phenobarbital will decrease the extent or impact of fentanyl transmucosal by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Observe Carefully. Coadministration of fentanyl with CYP3A4 inducers may lead to your reduce in fentanyl plasma concentrations, not enough efficacy or, potentially, progres