one, 7.2) ]. Risks of Concomitant Use or Discontinuation of Cytochrome P450 2D6 Inhibitors The concomitant usage of Promethazine with Codeine Oral Answer with all cytochrome P450 2D6 inhibitors (eg., amiodarone, quinidine) may possibly lead to an increase in codeine plasma concentrations and also a lessen in Energetic metabolite morphine plasma foc