1, seven.2) ]. Risks of Concomitant Use or Discontinuation of Cytochrome P450 2D6 Inhibitors The concomitant use of Promethazine with Codeine Oral Solution with all cytochrome P450 2D6 inhibitors (eg., amiodarone, quinidine) may perhaps cause an increase in codeine plasma concentrations as well as a minimize in Lively metabolite morphine plasma con