desvenlafaxine will raise the stage or impact of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Warning/Keep track of. Desvenlafaxine inhibits CYP2D6; with greater desvenlafaxine doses (ie, four hundred mg) decrease the CYP2D6 substrate dose by around 50%; no dosage adjustment desired with desvenlafaxine doses seven consecutive days pro