one, 7.two) ]. Dangers of Concomitant Use or Discontinuation of Cytochrome P450 2D6 Inhibitors The concomitant utilization of Promethazine with Codeine Oral Resolution with all cytochrome P450 2D6 inhibitors (eg., amiodarone, quinidine) may well end in a rise in codeine plasma concentrations and also a lessen in active metabolite morphine plasma fo