one, seven.two) ]. Pitfalls of Concomitant Use or Discontinuation of Cytochrome P450 2D6 Inhibitors The concomitant use of Promethazine with Codeine Oral Resolution with all cytochrome P450 2D6 inhibitors (eg., amiodarone, quinidine) could lead to an increase in codeine plasma concentrations as well as a reduce in active metabolite morphine plasma … Read More