desvenlafaxine will raise the level or influence of codeine by influencing hepatic enzyme CYP2D6 metabolism. Use Warning/Keep an eye on. Desvenlafaxine inhibits CYP2D6; with greater desvenlafaxine doses (ie, 400 mg) lessen the CYP2D6 substrate dose by up to fifty%; no dosage adjustment required with desvenlafaxine doses seven consecutive times righ