desvenlafaxine will raise the amount or impact of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Warning/Watch. Desvenlafaxine inhibits CYP2D6; with larger desvenlafaxine doses (ie, 400 mg) minimize the CYP2D6 substrate dose by up to fifty%; no dosage adjustment needed with desvenlafaxine doses seven consecutive times promptly before ge