desvenlafaxine will raise the stage or impact of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Warning/Watch. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, 400 mg) minimize the CYP2D6 substrate dose by as many as 50%; no dosage adjustment necessary with desvenlafaxine doses 7 consecutive times immediately just b