The effects of concomitant use or discontinuation of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with codeine are intricate, requiring mindful thought of the results to the guardian drug, codeine, plus the active metabolite, morphine.Usage of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with Promethazine VC wi