ritlecitinib will increase the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Intently. Ritlecitinib inhibits CYP3A4 substrates; coadministration raises AUC and peak plasma concentration delicate substrates, which may boost risk of adverse reactions.lumacaftor/ivacaftor will lower the le