Comparative Pharmacology of the Ketamine Isomers
نویسندگان
چکیده
Preliminary clinical studies with the ketamine isomers suggested that there were quantitative and qualitative differences between the enantiomers in their effects on the central nervous system (White et al., 1980). We reported differences between the optical isomers of ketamine in terms of their anaesthetic potency, intraoperative effects, postoperative analgesia and side-effects in surgical patients. Based on this earlier study, the more potent s(+) isomer appeared to offer significant clinical advantages over R(-) ketamine. Since racemic mixtures (of stereoisomers) do not necessarily behave as compounds containing equal proportions of the individual isomers (Haley and Gidley, 1970), further studies were needed to assess the potential advantages of S(+) ketamine compared with the currently available racemate (Ketalar, Ketaject). The present investigation was designed to evaluate the pharmacokinetic characteristics and pharmacodynamic effects of the optical isomers (v. racemic ketamine) in volunteers receiving the drugs in a controlled, cross-over fashion. The comparative effects of these drugs on the central nervous system (CNS) were assessed using clinical signs, the electroencephalogram (EEG), and a battery of psychometric tests. Finally, relationships between the serum concentrations of the three drugs and recovery times were used to assess their relative potencies.
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