Tramadol se demetiliše jetrenim enzimom CYP2D6[7] na isti način kao i kodein, tako da su poput odgovora na kodein, osobe koje imaju manje aktivnu formu CYP2D6 manje responsivne.
Dva enantiomera O-desmetiltramadola pokazuju veoma različite farmakološke profile.[8] Oba, (+) i (-)-O-desmetiltramadol, su neaktivna kao inhibitori preuzimanja serotonina,[9] ali (-)-O-desmetiltramadol zadržava aktivnost kao inhibitor noradrenalinskog preuzimanja[10].
↑Evan E. Bolton, Yanli Wang, Paul A. Thiessen, Stephen H. Bryant (2008). „Chapter 12 PubChem: Integrated Platform of Small Molecules and Biological Activities”. Annual Reports in Computational Chemistry4: 217-241. DOI:10.1016/S1574-1400(08)00012-1.
↑Borlak, J; Hermann, R; Erb, K; Thum, T (2003). „A rapid and simple CYP2D6 genotyping assay--case study with the analgetic tramadol”. Metabolism: clinical and experimental52 (11): 1439–43. DOI:10.1016/S0026-0495(03)00256-7. PMID14624403.
↑Garrido, MJ; Valle, M; Campanero, MA; Calvo, R; Trocóniz, IF (2000). „Modeling of the in vivo antinociceptive interaction between an opioid agonist, (+)-O-desmethyltramadol, and a monoamine reuptake inhibitor, (-)-O-desmethyltramadol, in rats”. The Journal of Pharmacology and Experimental Therapeutics295 (1): 352–9. PMID10992001.