Check Closely (1)lenacapavir will improve the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism.Coadministration with CYP3A4 substrates, notably All those with a slim therapeutic index, may lead to diminished concentrations and lack of efficacy. If not able to stay away from coadministration, check CYP3A4 substrat