desvenlafaxine will boost the level or influence of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Warning/Watch. Desvenlafaxine inhibits CYP2D6; with better desvenlafaxine doses (ie, 400 mg) reduce the CYP2D6 substrate dose by as many as fifty%; no dosage adjustment desired with desvenlafaxine doses 7 consecutive days right away just b