Challenges of Concomitant Use or Discontinuation of Cytochrome P450 2D6 Inhibitors The concomitant utilization of tramadol hydrochloride tablets with all cytochrome P450 2D6 inhibitors (e.g., amiodarone, quinidine) may well end in an increase in tramadol plasma amounts along with a minimize from the levels of the active metabolite, M1.When handling