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

Abstract

Glucuronidation catalyzed by uridine-5'-diphospho-glucuronosyl-transferases (UGTs) is the most important reaction in phase II metabolism of drugs and other compounds. O-glucuronidation is more common than N-glucuronidation. The anesthetic, analgesic and antidepressive drug ketamine is metabolized in phase I by cytochrome P450 enzymes to norketamine, hydroxynorketamine (HNK) diastereomers and dehydronorketamine (DHNK). Equine urine samples collected two hours after ketamine injection were treated with β-glucuronidase and analyzed with three enantioselective capillary electrophoresis assays. Concentrations of HNK diastereomers and norketamine were significantly higher in comparison to untreated urine and an increase of ketamine and DHNK levels was found in selected but not all samples. This suggests that O-glucuronides of HNK and N-glucuronides of the other compounds are formed in equines. N-glucuronidation of norketamine was studied in vitro with liver microsomes of different species and the single human enzyme UGT1A4. With equine liver microsomes (ELM) a stereoselective N-glucuronidation of norketamine was found that compares well to the results obtained with urines collected after ketamine administration. No reaction was observed with canine liver microsomes, human liver microsomes and UGT1A4. Incubation of ketamine and DHNK with ELM did not reveal any glucuronidation. Enantioselective CE is suitable to provide insight into the phase II metabolism of ketamine and its metabolites.

Sex-dependent metabolism of ketamine and (2R,6R)-hydroxynorketamine in mice and humans

“…HNKs undergo glucuronide conjugation, which is catalyzed at least partly by the uridine 5’-diphospho(UDP)-glucuronosyltransferase UGT2B4 (Moaddel et al, 2010). HNKs are eliminated both in their conjugated and unconjugated forms in urine and bile (Chang and Glazko, 1974; Dinis-Oliveira, 2017; Lankveld et al, 2006; Moaddel et al, 2010; Sandbaumhuter and Thormann, 2018; Turfus et al, 2009).…”

Hydroxynorketamines: Pharmacology and Potential Therapeutic Applications

“…HNKs undergo glucuronide conjugation, at least partly catalyzed by the UDP-glucuronosyltransferase isoform UGT2B4 (Moaddel et al, 2010), and are eliminated both in their unconjugated and conjugated forms in urine and bile (Chang and Glazko, 1974;Lankveld et al, 2006;Turfus et al, 2009;Moaddel et al, 2010;Dinis-Oliveira, 2017;Sandbaumhüter and Thormann, 2018). In mice, HNKs are detected up to 2-4 hours in the plasma and brain after intraperitoneal ketamine administration (Zanos et al, 2016(Zanos et al, , 2019a.…”

Advances of capillary electrophoresis enantioseparations in pharmaceutical analysis (2017–2020)

“…It was clearly shown that hydroxylated metabolites other than 6‐hydroxynorketamine were formed in the in vitro incubations and could also be detected in the plasma samples. In a subsequent study, the dual selector system was applied in combination with further methods, i.e., 2% (m/v) HS‐γ‐CD in a 17.8 mM Tris‐phosphoric acid buffer, pH 2.0, under reversed polarity of the applied voltage and 0.66% (m/v) HS‐γ‐CD in 100 mM sodium phosphate buffer, pH 3.0, in order to separate all metabolites in equine urine and to exclude interferences by endogenous compounds [141]. Furthermore, the samples were analyzed before and after treatment with β‐glucuronidase and arylsulfates to conclude on the phase‐II metabolism of the drug.…”