title: Pharmacokinetics of ketamine and three metabolites in Beagle dogs under sevoflurane vs. medetomidine comedication assessed by enantioselective capillary electrophoresis.
abstract: Ketamine is often used for anesthesia in veterinary medicine. One possible comedication is the sedative α2-agonist medetomidine. Advantages of that combination are the compensation of side effects of the two drugs and the anesthetic-sparing effect of medetomidine. In vitro studies showed that medetomidine has an inhibitive effect on the formation of norketamine. Norketamine is the first metabolite of ketamine and is also active. It is followed by others like 6-hydroxynorketamine and 5,6-dehydronorketamine (DHNK). In an in vivo pharmacokinetic study Beagle dogs under sevoflurane anesthesia (mean end-tidal concentration 3.0±0.2%) or following medetomidine sedation (450μg/m2) received 4mg/kg racemic ketamine or 2mg/kg S-ketamine. Blood samples were collected between 0 and 900min after drug injection. 50μL aliquots of plasma were pretreated by liquid-liquid extraction prior to analysis of the reconstituted extracts with a robust enantioselective capillary electrophoresis assay using highly sulfated γ-cyclodextrin as chiral selector and electrokinetic sample injection of the analytes from the extract across a short buffer plug without chiral selector. Levels of S- and R-ketamine, S- and R-norketamine, (2S,6S)- and (2R,6R)-hydroxynorketamine and S- and R-DHNK were determined. Data were analyzed with compartmental pharmacokinetic models which included two compartments for the ketamine and norketamine enantiomers and a single compartment for the DHNK and 6-hydroxynorketamine stereoisomers. Medetomidine showed an effect on the formation and elimination of all metabolites. Stereoselectivities were detected for 6-hydroxynorketamine and DHNK, but not for ketamine and norketamine.
authors.affiliation: Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
authors.forename: Friederike A
authors.initials: FA
authors.lastname: Sandbaumhüter
authors.affiliation: Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
authors.forename: Regula
authors.initials: R
authors.lastname: Theurillat
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors.forename: Rima N
authors.initials: RN
authors.lastname: Bektas
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors.forename: Annette P N
authors.initials: APN
authors.lastname: Kutter
authors.affiliation: Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zürich, Zürich, Switzerland.
authors.forename: Regula
authors.initials: R
authors.lastname: Bettschart-Wolfensberger
authors.affiliation: Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Bern, Bern, Switzerland. Electronic address: wolfgang.thormann@ifik.unibe.ch.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Thormann
mesh_terms: D000778:Anesthetics, Dissociative / Q000493:pharmacokinetics*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001711:Biotransformation; D004285:Dogs; D004347:Drug Interactions; D019075:Electrophoresis, Capillary; D005260:Female; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007649:Ketamine / Q000031:analogs & derivatives / Q000737:chemistry / Q000493:pharmacokinetics*; D008297:Male; D020926:Medetomidine / Q000494:pharmacology*; D008738:Methyl Ethers / Q000494:pharmacology*; D000077149:Sevoflurane; D013237:Stereoisomerism; D047408:gamma-Cyclodextrins / Q000737:chemistry
chemical_list: D000778:Anesthetics, Dissociative; D018685:Anesthetics, Inhalation; D006993:Hypnotics and Sedatives; D008738:Methyl Ethers; D047408:gamma-Cyclodextrins; D000077149:Sevoflurane; C033420:5,6-dehydronorketamine; D007649:Ketamine; C050654:6-hydroxynorketamine; D020926:Medetomidine; C033419:norketamine
keywords: Dehydronorketamine; Enantioselective capillary electrophoresis; Hydroxynorketamine; Ketamine; Medetomidine; Pharmacokinetics