Enantioselective analysis of ketamine and its metabolites in equine plasma and urine by CE with multiple isomer sulfated beta-CD.

The study conducted an analysis of ketamine and its metabolites in horse plasma and urine, using CE with multiple sulfated beta-CD isomer as the choosy selector. The research found that different commercial selectors varied the separability of ketamine enantiomers, and concluded that a mix of two lots provides clear detection of enantiomers in liquid extracts of plasma and urine. The research also discovered that higher urinary amounts of R-ketamine were present in horses anaesthetized with isoflurane and treated with ketamine infusion.

Methodology and Approach

• The study utilized Capillary Electrophoresis (CE) with multiple isomer sulfated beta-cyclodextrin (beta-CD) as a chiral selector to simultaneously analyze enantiomers of ketamine and its metabolites present in equine plasma and urine extracts.
• The oscillations of commercial chiral selectors were assessed to determine their effect on the separability of ketamine enantiomers.
• The study used high-performance liquid chromatography (HPLC), Liquid Chromatography-Mass Spectrometry (LC-MS), and Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS) techniques to identify ketamine, norketamine, and dehydronorketamine in urinary extracts.
• The inherent bias or stereoselectivity of the compounds was observed by putting the CE assay to use, evaluating the samples of five ponies anesthetized with isoflurane in oxygen and administered intravenous continuous infusion of racemic ketamine.

Findings and Conclusion

• The research found that varying batches of the commercial chiral selector drastically changed the enantiomeric separability of ketamine, suggesting underlying production inconsistencies.
• Through trial and error, it was discovered that a blend of two batches gave the most satisfactory output, enabling high-resolution separation and uncontaminated detection of enantiomers in the liquid extracts from equine plasma and urine.
• Both LC-MS and LC-MS/MS were able to distinctly pinpoint ketamine, norketamine, and dehydronorketamine in the samples with high precision.
• The study observed that although the concentrations of the ketamine enantiomers in plasma are equal, their urinary presence differed, with R-ketamine being larger than S-ketamine.
• The analysis also revealed that plasma and urine contain higher S- than R-norketamine concentrations and the average S-/R-enantiomer proportions of dehydronorketamine in both sample types were lower than one and closely matched.