Enantioselective capillary electrophoresis provides insight into the phase II metabolism of ketamine and its metabolites in vivo and in vitro.

This research article explores how ketamine, a drug used for anaesthetics, and its metabolites are metabolized in phase II by the process of glucuronidation. This process, catalyzed by uridine-5′-diphospho-glucuronosyl-transferases (UGTs), is essential for the metabolism of drugs and various compounds. A test is carried out using equine liver microsomes, highlighting insights into the phase II metabolism of ketamine and its metabolites.

Understanding Phase II Metabolism

• Phase II metabolism primarily involves glucuronidation, a reaction facilitated by enzymes known as uridine-5′-diphospho-glucuronosyl-transferases (UGTs).
• The metabolism of ketamine, a widely-used anesthetic and antidepressive drug, is broken down by cytochrome P450 enzymes into substances called norketamine, hydroxynorketamine (HNK) diastereomers, and dehydronorketamine (DHNK).
• The study presents insight into how O-glucuronides of HNK and N-glucuronides of other compounds are produced in equines by examining equine urine samples. This suggests the role of UGTs in drug metabolism.

Ketamine Metabolization in Equines

• To understand the metabolization process, equine urine samples were taken two hours after ketamine injection, treated with β-glucuronidase, and analyzed using enantioselective capillary electrophoresis assays.
• The findings indicated higher concentrations of HNK diastereomers and norketamine compared to untreated urine. Interestingly, increased levels of ketamine and DHNK were found in selected but not all samples.

In Vitro Study of Norketamine Glucuronidation

• N-Glucuronidation of norketamine was examined using liver microsomes of different species and the single human enzyme UGT1A4.
• A stereoselective N-glucuronidation of norketamine was observed when equine liver microsomes were involved, showing consistency with results from urines collected post-ketamine administration.
• However, no reaction was witnessed with canine liver microsomes, human liver microsomes, and UGT1A4. Also, when both ketamine and DHNK were incubated with ELM, no glucuronidation occurred.

Insights into Phase II Metabolism of Ketamine

• This research highlights how enantioselective capillary electrophoresis is a valuable tool for understanding the phase II metabolism of ketamine and its metabolites, providing knowledge that could be crucial in developing more effective drug treatments and therapy strategies in the future.