1, seven.two) ]. Dangers of Concomitant Use or Discontinuation of Cytochrome P450 2D6 Inhibitors The concomitant utilization of Promethazine with Codeine Oral Alternative with all cytochrome P450 2D6 inhibitors (eg., amiodarone, quinidine) could end in a rise in codeine plasma concentrations as well as a minimize in Lively metabolite morphine plasm