title: Stereoselective pharmacokinetics of ketamine and norketamine after racemic ketamine or S-ketamine administration in Shetland ponies sedated with xylazine.
abstract: The pharmacokinetics of ketamine and norketamine enantiomers after administration of intravenous (IV) racemic ketamine (R-/S-ketamine; 2.2 mg/kg) or S-ketamine (1.1 mg/kg) to five ponies sedated with IV xylazine (1.1mg/kg) were compared. The time intervals to assume sternal and standing positions were recorded. Arterial blood samples were collected before and 1, 2, 4, 6, 8 and 13 min after ketamine administration. Arterial blood gases were evaluated 5 min after ketamine injection. Plasma concentrations of ketamine and norketamine enantiomers were determined by capillary electrophoresis and were evaluated by non-linear least square regression analysis applying a monocompartmental model. The first-order elimination rate constant was significantly higher and elimination half-life and mean residence time were lower for S-ketamine after S-ketamine compared to R-/S-ketamine administration. The maximum concentration of S-norketamine was higher after S-ketamine administration. Time to standing position was significantly diminished after S-ketamine compared to R-/S-ketamine. Blood gases showed low-degree hypoxaemia and hypercarbia.
authors.affiliation: Anaesthesiology Section, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, Bern, Switzerland.
authors.forename: M Paula
authors.initials: MP
authors.lastname: Larenza
authors.forename: Monika
authors.initials: M
authors.lastname: Knobloch
authors.forename: M Fabiana
authors.initials: MF
authors.lastname: Landoni
authors.forename: Olivier L
authors.initials: OL
authors.lastname: Levionnois
authors.forename: Peter W
authors.initials: PW
authors.lastname: Kronen
authors.forename: Regula
authors.initials: R
authors.lastname: Theurillat
authors.forename: Urs
authors.initials: U
authors.lastname: Schatzmann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Thormann
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage; D000768:Anesthesia, General / Q000379:methods / Q000662:veterinary*; D019162:Anesthetics, Combined / Q000097:blood / Q000493:pharmacokinetics; D000778:Anesthetics, Dissociative / Q000493:pharmacokinetics*; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D018592:Cross-Over Studies; D006736:Horses / Q000097:blood / Q000502:physiology*; D007649:Ketamine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D011897:Random Allocation; D013237:Stereoisomerism; D014991:Xylazine / Q000008:administration & dosage
chemical_list: D000316:Adrenergic alpha-Agonists; D019162:Anesthetics, Combined; D000778:Anesthetics, Dissociative; D014991:Xylazine; D007649:Ketamine; C033419:norketamine