desvenlafaxine will boost the level or result of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Warning/Keep track of. Desvenlafaxine inhibits CYP2D6; with better desvenlafaxine doses (ie, 400 mg) reduce the CYP2D6 substrate dose by around 50%; no dosage adjustment essential with desvenlafaxine doses seven consecutive times instantly ju