desvenlafaxine will boost the amount or effect of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Caution/Keep an eye on. Desvenlafaxine inhibits CYP2D6; with greater desvenlafaxine doses (ie, four hundred mg) lessen the CYP2D6 substrate dose by around fifty%; no dosage adjustment required with desvenlafaxine doses 7 consecutive days ins