desvenlafaxine will increase the degree or outcome of codeine by influencing hepatic enzyme CYP2D6 metabolism. Use Warning/Monitor. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, four hundred mg) minimize the CYP2D6 substrate dose by nearly fifty%; no dosage adjustment needed with desvenlafaxine doses 7 consecutive days insta