• O Matouskova, O Slanar, L Chytil, and F Perlik.
• Clinical Pharmacology Unit, Institute of Pharmacology, 1st Faculty of Medicine, Charles University, Prague, Czech Republic.
• J Clin Pharm Ther. 2011 Aug 1;36(4):513-7.

What Is Known And ObjectiveThe opioid effect of tramadol, which can be detected by pupillary response, is predominantly mediated by the O-demethylated metabolite, formed via CYP2D6. This study was designed to evaluate the effects of tramadol using different parameters of pupillometry as biomarkers.MethodsSixty-nine healthy volunteers received tramadol hydrochloride drops orally at a dose of 0·7 mg/kg. Pre-dose and 2-h post-dose pupillometric measurements were performed. The polymorphism of CYP2D6 was analysed.Results And DiscussionLarge interindividual variability was observed in the tramadol-induced pupillary reaction. Miosis was induced in 69·6% and mydriasis in 30·4% of the subjects. The pupillary response differed in relation to the CYP2D6 genotype. A maximal difference in initial pupil diameter of 0·81 mm was found in extensive metabolizers. There were significant effects observed on the pupillary light reflex parameters with tramadol administration (P < 0·05) except for the reflex amplitude and constriction velocity.What Is New And ConclusionThe pharmacodynamic effects of tramadol were easily detected using both static and dynamic pupil parameters. The pharmacodynamic profiles were markedly influenced by the CYP2D6 phenotype.© 2010 The Authors. JCPT © 2010 Blackwell Publishing Ltd.

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