desvenlafaxine will boost the stage or influence of codeine by influencing hepatic enzyme CYP2D6 metabolism. Use Warning/Check. Desvenlafaxine inhibits CYP2D6; with better desvenlafaxine doses (ie, 400 mg) minimize the CYP2D6 substrate dose by nearly 50%; no dosage adjustment essential with desvenlafaxine doses seven consecutive times right away pr