Tramadol is metabolized to M1 by CYP2D6. Quinidine is actually a selective inhibitor of that isoenzyme, in order that concomitant administration of quinidine and tramadol hydrochloride tablets results in increased concentrations of tramadol and lowered concentrations of M1. We will cover which ones are possible (there are a few) in https://neils108ekp3.wikitron.com/user