ribociclib will improve the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism.Check Closely (2)efavirenz will lower the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep track of Intently. Coadministration of fentanyl with CYP3A4 inducers could lead on to the