desvenlafaxine will raise the stage or result of codeine by impacting hepatic enzyme CYP2D6 metabolism. Use Caution/Observe. Desvenlafaxine inhibits CYP2D6; with better desvenlafaxine doses (ie, four hundred mg) reduce the CYP2D6 substrate dose by approximately fifty%; no dosage adjustment wanted with desvenlafaxine doses seven consecutive times st