Contraindicated. Cobicistat is a CYP3A4 inhibitor; contraindicated with CYP3A4 substrates for which elevated plasma concentrations are affiliated with severe and/or life-threatening functions.iloperidone improves levels of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Check. Iloperidone is a time-dependent CYP3A i