Clin Pharmacokinet
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Tramadol hydrochloride is used worldwide as an analgesic drug with a unique dual function. The metabolic enzymes cytochrome P450 (CYP) 3A4, CYP2B6, and CYP2D6 and the various transporters [adenosine triphosphate-binding cassette B1/multidrug resistance 1/P-glycoprotein, organic cation transporter 1, serotonin transporter (SERT), norepinephrine transporter (NET)] and receptor genes (opioid receptor μ 1 gene) give possible genetic differences that might affect the pharmacokinetics and/or pharmacodynamics of tramadol. Therefore, the aim of this review is to present a systematic walkthrough of all possible genetic factors involved in the pharmacology of tramadol. ⋯ In this systematic review, the current knowledge on all possible genetic factors that might influence the metabolism or clinical efficacy of tramadol has been collected and summarized. Only the effect of CYP2D6 polymorphisms on the metabolism of tramadol and the consequent effect on pain relief has been thoroughly studied and sufficiently established as clinically relevant.