desvenlafaxine will raise the level or influence of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Caution/Keep an eye on. Desvenlafaxine inhibits CYP2D6; with greater desvenlafaxine doses (ie, 400 mg) decrease the CYP2D6 substrate dose by approximately 50%; no dosage adjustment required with desvenlafaxine doses 7 consecutive days prom… Read More