This is a cross-over group, double-blind, randomized clinical trial in healthy volunteers comparing dextromethorphan and inactive control on freeze-induced hyperalgesia, experimental pain, diffuse noxious inhibitory control (DNIC), pupillary reaction and reaction time.~The influence of CYP3A4 and MDR1 polymorphism on the dextromethorphan analgesic efficacy will be measured.~The study design is divided in two study sequences and each subject participates in the two study sequences and receive the two treatments (dextromethorphan and placebo).~Each study sequence consists of 3 assessment days (Day -1, Day 0 = first treatment administration and Day 1).
The aim of this study is to assess the anti-hyperalgesic effect of dextromethorphan in healthy volunteers compared to placebo.