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Hubbell JAE, Muir WW, Gorenberg E, Hopster K. A review of equine anesthetic induction: Are all equine anesthetic inductions "crash" inductions? J Equine Vet Sci 2024; 139:105130. [PMID: 38879096 DOI: 10.1016/j.jevs.2024.105130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/29/2024] [Accepted: 06/12/2024] [Indexed: 06/29/2024]
Abstract
Horses are the most challenging of the common companion animals to anesthetize. Induction of anesthesia in the horse is complicated by the fact that it is accompanied by a transition from a conscious standing position to uncconconscious recumbency. The purpose of this article is to review the literature on induction of anesthesia with a focus on the behavioral and physiologic/pharmacodynamic responses and the actions and interactions of the drugs administered to induce anesthesia in the healthy adult horse with the goal of increasing consistency and predictability.
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Affiliation(s)
| | - William W Muir
- College of Veterinary Medicine, Lincoln Memorial University, Harrogate, Tennessee, USA
| | - Emma Gorenberg
- School of Veterinary Medicine, University of Pennsylvania. Kennett Square, PA, USA
| | - Klaus Hopster
- School of Veterinary Medicine, University of Pennsylvania. Kennett Square, PA, USA
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2
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Kumari Rayala VVSP, Kandula JS, P R. Advances and challenges in the pharmacokinetics and bioanalysis of chiral drugs. Chirality 2022; 34:1298-1310. [PMID: 35883279 DOI: 10.1002/chir.23495] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/05/2022] [Accepted: 07/12/2022] [Indexed: 02/06/2023]
Abstract
Enantioselective analytical approaches are essential for monitoring pharmacokinetics and acquiring accurate data to better understand the role of stereochemistry in pharmacokinetics. Enantioselectivity significantly impacts the pharmacokinetics of chiral drugs, especially in metabolic profile, leading to toxicity of enantiomer. Consequently, there is a need to study the pharmacokinetics of enantiomerically pure drugs and racemates as they differ in affinity with enzymes and proteins. Combining the best enantioseparation conditions with the specified biological matrix and the intended purpose of the analysis is a challenging task. This review discusses the importance of chirality in stereoselective pharmacokinetics with more relevant examples, various enantioselective analytical techniques, and stationary phases employed. Challenges such as lack of universal chiral columns, biological inversion of the isomers, and others have been discussed. Further presented the recent advances in the screening of chiral drugs and innovative improvements in the analytical approaches for chiral molecule analysis such as supercritical fluid chromatography, simulated moving bed chromatography, and other techniques are discussed.
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Affiliation(s)
- V V S Prasanna Kumari Rayala
- Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research (NIPER), Guwahati, Assam, India
| | - Jony Susanna Kandula
- Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research (NIPER), Guwahati, Assam, India
| | - Radhakrishnanand P
- Department of Pharmaceutical Analysis, National Institute of Pharmaceutical Education and Research (NIPER), Guwahati, Assam, India
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Levionnois OL, Barbarossa A, Bardhi A, Siegenthaler J, Forss Pleyers T, Guidi M, Spadavecchia C, Raillard M. Enantiospecific pharmacokinetics of intravenous dexmedetomidine in beagles. J Vet Pharmacol Ther 2022; 45:366-372. [PMID: 35484944 PMCID: PMC9543782 DOI: 10.1111/jvp.13063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 03/12/2022] [Accepted: 04/15/2022] [Indexed: 11/30/2022]
Abstract
The goal of this study was to investigate the pharmacokinetic (PK) behaviour of dexmedetomidine in dogs administered as a pure enantiomer versus as part of a racemic mixture. Eight unmedicated intact purpose‐bread beagles were included. Two intravenous treatments of either medetomidine or dexmedetomidine were administered at 10‐ to 14‐day intervals. Atipamezole or saline solution was administered intramuscularly 45 min later. Venous blood samples were collected into EDTA collection tubes, and the quantification of dexmedetomidine and levomedetomidine was performed by chiral LC–MS/MS. All dogs appeared sedated after each treatment without complication. Plasma concentrations of levomedetomidine were measured only in the racemic group and were 51.4% (51.4%–56.1%) lower than dexmedetomidine. Non‐compartmental analysis (NCA) was performed for both drugs, while dexmedetomidine data were further described using a population pharmacokinetic approach. A standard two‐compartment mammillary model with linear elimination with combined additive and multiplicative error model for residual unexplained variability was established for dexmedetomidine. An exponential model was finally retained to describe inter‐individual variability on parameters of clearance (Cl1) and central and peripheral volumes of distribution (V1, V2). No effect of occurrence, levomedetomidine or atipamezole could be observed on dexmedetomidine PK parameters. Dexmedetomidine did not undergo significantly different PK when administered alone or as part of the racemic mixture in otherwise unmedicated dogs.
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Affiliation(s)
- Olivier Louis Levionnois
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Andrea Barbarossa
- Department of Veterinary Medical Sciences, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - Anisa Bardhi
- Department of Veterinary Medical Sciences, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - Joelle Siegenthaler
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Tekla Forss Pleyers
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Monia Guidi
- Service of Clinical Pharmacology, Department of Laboratory Medicine and Pathology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,Center for Research and Innovation in Clinical Pharmaceutical Sciences, Teaching and Research Department, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Claudia Spadavecchia
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Mathieu Raillard
- Section of Anaesthesiology and Pain Therapy, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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Becker S, Maier A, Peters S, Büttner K, Reiner G. S-ketamine and intranasal application: alternatives for the castration of male suckling piglets? BMC Vet Res 2021; 17:122. [PMID: 33726749 PMCID: PMC7968208 DOI: 10.1186/s12917-021-02826-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 03/02/2021] [Indexed: 11/24/2022] Open
Abstract
Background The intramuscular injection of ketamine and azaperone was proposed as a suitable anaesthesia for male suckling piglets for surgical castration. However, this can be opposed by massive defensive movements, hypothermia and tachycardia during castration and a long recovery period. The aim of the present study was to test whether the use of S-ketamine and/or a change in the route of application from intramuscular to intranasal could reduce stress responses and the duration of recovery compared to the intramuscular route and the use of racemic ketamine. Seventy-eight healthy, five-day-old male piglets were randomized to six treatment groups in a blinded experimental study, matched by litter and weight. Experimental groups were A (15 mg kg-1 S-ketamine + 2 mg kg-1 azaperone, i.m., surgical castration), B (15 mg kg-1 R/S-ketamine racemate + 2 mg kg-1 azaperone, i.m., surgical castration), C (30 mg kg-1 S-ketamine + 2 mg kg-1 azaperone, i.n., surgical castration), D (15 mg kg-1 R/S-ketamine racemate + 2 mg kg-1 azaperone, i.m.; not castrated), E (positive control group; no anesthesia, surgical castration) and F (negative control group; no anesthesia, not castrated). Results S-ketamine reduced the defensive movement score during castration to a similar extent to racemic ketamine when administered intramuscularly but not via the intranasal route. However, the effects of S-ketamine (both routes) on the increase in cortisol levels and decrease in body temperature were similar to those induced by racemic ketamine. A reduction of the long recovery time known for ketamine-azaperone anaesthesia could not be achieved with S-ketamine in the given dosage, regardless of the route of application. The intranasal administration of ketamine was difficult with the available formulation as the necessary amount exceeded the capacity of the nose cavity. Conclusions Neither the use of S-ketamine nor intranasal administration can be suitable alternatives for the anaesthesia of male suckling piglets for castration.
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Affiliation(s)
- Sabrina Becker
- Department for Clinical Veterinary Sciences, Clinic for Swine, Justus-Liebig-University, Giessen, Germany
| | - Anna Maier
- Department for Clinical Veterinary Sciences, Clinic for Swine, Justus-Liebig-University, Giessen, Germany
| | - Saskia Peters
- Department of Animal Welfare, Justus-Liebig-University, Giessen, Germany
| | - Kathrin Büttner
- Unit for Biomathematics and Data Processing, Faculty of Veterinary Medicine, Justus Liebig University, Frankfurter Str. 95, 35392, Giessen, Germany
| | - Gerald Reiner
- Department for Clinical Veterinary Sciences, Clinic for Swine, Justus-Liebig-University, Giessen, Germany.
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Wang J, Wang Y, Xu X, Peng S, Xu F, Liu P. Use of Various Doses of S-Ketamine in Treatment of Depression and Pain in Cervical Carcinoma Patients with Mild/Moderate Depression After Laparoscopic Total Hysterectomy. Med Sci Monit 2020; 26:e922028. [PMID: 32565534 PMCID: PMC7331479 DOI: 10.12659/msm.922028] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background This study investigated the effects of various doses of S-ketamine on depression and pain management of cervical carcinoma patients with mild/moderate depression. Material/Methods This randomized, double-blind, controlled study included 417 cervical carcinoma patients who received laparoscopic modified radical hysterectomy from April 2015 to July 2018 and who also had mild/moderate depression symptoms based on HAMD-17 scores (8~24). All patients were randomized into 4 groups: 1) the control group, 2) the racemic ketamine group, 3) the high-dose S-ketamine group; and 4) the low-dose S-ketamine group. Pain was assessed using the Visual Analogue Score (VAS), and depression was assessed using theHAMD-17 score. Serum levels of BDNF and 5-HT were measured. Results The 4 groups of patients showed no significant differences in operation time, bleeding volume, hospitalization duration, or complications. The high-dose S-ketamine group showed significantly lower VAS and HAMD-17 scores than all other groups at 1 day and 3 days postoperatively, but no differences were observed in the low-dose S-ketamine group and the racemic ketamine group. The high-dose S-ketamine group showed significantly higher serum BDNF and 5-HT levels at 1 day and 3 days after surgery. However, 1 week after surgery, no difference was observed in any of the treatment groups. Conclusions At subanesthetic dose, both 0.5 mg/kg and 0.25 mg/kg S-ketamine improved short-term depression and pain for cervical carcinoma patients after surgery, and the effects were better than with the same dose of racemic ketamine.
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Affiliation(s)
- Jie Wang
- Department of Anesthesiology, Ninth People's Hospital of Suzhou, Suzhou, Jiangsu, China (mainland)
| | - Yajun Wang
- Department of Anesthesiology, Xishan People's Hospital, Wuxi, Jiangsu, China (mainland)
| | - Xudong Xu
- Department of Anesthesiology, Changzhou Traditional Chinese Medicine Hospital, Changzhou, Jiangsu, China (mainland)
| | - Sheng Peng
- Department of Anesthesiology, Seventh People's Hospital of Shanghai University of Traditional Chinese Medicine (TCM), Shanghai, China (mainland)
| | - Feng Xu
- Department of Medical Oncology, Shanghai Gongli Hospital, Second Military Medical University, Shanghai, China (mainland)
| | - Peirong Liu
- Department of Anesthesiology, Seventh People's Hospital of Shanghai University of Traditional Chinese Medicine (TCM), Shanghai, China (mainland)
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Romagnoli N, Bektas RN, Kutter AP, Barbarossa A, Roncada P, Hartnack S, Bettschart-Wolfensberger R. Pharmacokinetics of S-ketamine and R-ketamine and their active metabolites after racemic ketamine or S-ketamine intravenous administration in dogs sedated with medetomidine. Vet Anaesth Analg 2020; 47:168-176. [DOI: 10.1016/j.vaa.2019.08.048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/08/2019] [Accepted: 08/19/2019] [Indexed: 11/29/2022]
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Thormann W. Capillary electrophoresis for the determination of drugs in biological fluids. HANDBOOK OF ANALYTICAL SEPARATIONS 2020. [DOI: 10.1016/b978-0-444-64066-6.00004-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Romagnoli N, Bektas RN, Kutter AP, Barbarossa A, Roncada P, Hartnack S, Bettschart-Wolfensberger R. Pharmacokinetics of ketamine and norketamine enantiomers after racemic or S-ketamine IV bolus administration in dogs during sevoflurane anaesthesia. Res Vet Sci 2017; 112:208-213. [DOI: 10.1016/j.rvsc.2017.05.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 05/03/2017] [Accepted: 05/05/2017] [Indexed: 11/26/2022]
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Sandbaumhüter FA, Theurillat R, Thormann W. Separation of hydroxynorketamine stereoisomers using capillary electrophoresis with sulfated β-cyclodextrin and highly sulfated γ-cyclodextrin. Electrophoresis 2017; 38:1878-1885. [PMID: 28213944 DOI: 10.1002/elps.201700016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 02/09/2017] [Accepted: 02/14/2017] [Indexed: 01/17/2023]
Abstract
The racemic N-methyl-d-aspartate receptor antagonist ketamine is used in anesthesia, analgesia and the treatment of depressive disorders. It is known that interactions of hydroxylated norketamine metabolites and 5,6-dehydronorketamine (DHNK) with the α7 -nicotinic acetylcholine receptor and the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor are responsible for the antidepressive effects. Ketamine and its first metabolite norketamine are not active on these receptors. As stereoselectivity plays a role in ketamine metabolism, a cationic capillary electrophoresis based method capable of resolving and analyzing the stereoisomers of four hydroxylated norketamine metabolites, norketamine and DHNK was developed. The assay is based on liquid/liquid extraction of the analytes from the biological matrix, electrokinetic sample injection across a buffer plug and analysis of the stereoisomers in a phosphate background electrolyte (BGE) at pH 3 comprising a mixture of sulfated β-cyclodextrin (5 mg/mL) and highly sulfated γ-cyclodextrin (0.1%). The method was used to analyze samples of an in vitro study in which ketamine was incubated with equine liver microsomes and in plasma samples of dogs and horses that were collected after an i.v. bolus injection of racemic ketamine.
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Affiliation(s)
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, University of Bern, Bern, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, University of Bern, Bern, Switzerland
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Li W, Li G, Zhong Z, Xie B, Zhou Z, Gu W, Shi X, Tang T, Ai S, Fu H, Liu M, Liu M, Wu D, Hu Y, Peng G. Validation of an HPLC assay for determination of Telazol in pregnant pigs: application to placental transfer study. J Vet Med Sci 2017; 79:801-806. [PMID: 28302956 PMCID: PMC5402205 DOI: 10.1292/jvms.16-0300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Anesthetics utilized for the immobilization of pregnant mammals are prone to crossing the
placental barrier and cause adverse effects to the fetuses. In this study, we develop a
facile method employing high performance liquid chromatography (HPLC) for the study of
Telazol crossing the placental barrier of pregnant pigs. The method mainly relies on the
efficient extraction strategy that includes the mobile phase composed of 10 mM ammonium
acetate aqueous solution-acetonitrile (1:4, v/v). When the injected dose of Telazol is 10
mg/kg (5 mg/kg of each constituent drug, zolazepem and tiletamine), zolazepam can cross
the placental barrier as it is detected in both uterus and umbilical cord with
approximately the same content. Conversely, tiletamine is detected in neither uterus nor
umbilical cord, indicating the absence of placental transfer of tiletamine. The different
absorption rates of the two dosage-equal compounds by pigs are found to be the main cause
of their different abilities to cross the placental barrier.
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Affiliation(s)
- Wei Li
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Gangshi Li
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Zhijun Zhong
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Bingbing Xie
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Ziyao Zhou
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Wuyang Gu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Xianpeng Shi
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Tianliang Tang
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Shengquan Ai
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Hualin Fu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Mengjiao Liu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Mengxi Liu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - De Wu
- Institute of Animal Nutrition, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Yanchun Hu
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
| | - Guangneng Peng
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, College of Veterinary Medicine, Sichuan Agricultural University, Ya'an 625014, P. R. China
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Weiland LC, Kluge K, Kutter APN, Kronen PW. Clinical evaluation of intranasal medetomidine-ketamine and medetomidine-S(+)-ketamine for induction of anaesthesia in rabbits in two centres with two different administration techniques. Vet Anaesth Analg 2017; 44:98-105. [PMID: 27374385 DOI: 10.1111/vaa.12408] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 03/04/2016] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The aim was to compare efficacy and side effects of induction with medetomidine-ketamine or medetomidine-S(+)-ketamine by intranasal (IN) instillation in rabbits and to evaluate both protocols during subsequent isoflurane anaesthesia. STUDY DESIGN Prospective, blinded, randomized experimental study in two centres. ANIMALS Eighty-three healthy New Zealand White rabbits undergoing tibial or ulnar osteotomy. METHODS Medetomidine (0.2 mg kg-1) with 10 mg kg-1 ketamine (MK) or 5 mg kg-1 S(+)-ketamine (MS) was administered IN to each rabbit in a randomized fashion. In Centre 1 (n = 42) rabbits were held in sternal recumbency, and in Centre 2 (n = 41) in dorsal recumbency, during drug instillation. Adverse reactions were recorded. If a rabbit swallowed during endotracheal intubation, half of the initial IN dose was repeated and intubation was re-attempted after 5 minutes. Anaesthesia was maintained with isoflurane. Heart rate, blood pressure, endtidal carbon dioxide concentration and blood gases were recorded. Data were analysed using Student's t-test, Mann-Whitney test and Fisher's exact test. RESULTS In all, 39 animals were assigned to the MK group and 44 to the MS group. Two rabbits in the MS group held in dorsal recumbency died after instillation of the drug. Eight (MK) and 11 rabbits (MS) were insufficiently anaesthetized and received a second IN dose. One rabbit in MK and three in MS required an isoflurane mask induction after the second IN dose. There were no significant differences between treatments for induction, intraoperative data, blood gas values and recovery data. CONCLUSION AND CLINICAL RELEVANCE This study indicated that medetomidine-ketamine and medetomidine-S(+)-ketamine were effective shortly after IN delivery, but in dorsal recumbency IN administration of S(+)-ketamine led to two fatalities. Nasal haemorrhage was noted in both cases; however, the factors leading to death have not been fully elucidated.
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Affiliation(s)
- Linda C Weiland
- VAS, Veterinary Anaesthesia Services-International, Winterthur, Switzerland
| | - Katharina Kluge
- Preclinical Surgery, AO Research Institute, Davos Platz, Switzerland
| | - Annette P N Kutter
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty University of Zurich, Zurich, Switzerland
| | - Peter W Kronen
- VAS, Veterinary Anaesthesia Services-International, Winterthur, Switzerland; Centre for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland.
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12
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Sandbaumhüter FA, Theurillat R, Bektas RN, Kutter AP, Bettschart-Wolfensberger R, Thormann W. Pharmacokinetics of ketamine and three metabolites in Beagle dogs under sevoflurane vs. medetomidine comedication assessed by enantioselective capillary electrophoresis. J Chromatogr A 2016; 1467:436-444. [DOI: 10.1016/j.chroma.2016.07.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 07/13/2016] [Accepted: 07/23/2016] [Indexed: 12/27/2022]
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13
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Menzies MPL, Ringer SK, Conrot A, Theurillat R, Kluge K, Kutter AP, Jackson M, Thormann W, Bettschart-Wolfensberger R. Cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane and low-dose S-ketamine or medetomidine infusions. Vet Anaesth Analg 2016; 43:623-634. [PMID: 26915545 DOI: 10.1111/vaa.12359] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 09/17/2015] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To evaluate cardiopulmonary effects and anaesthesia recovery quality in horses anaesthetized with isoflurane receiving medetomidine or S-ketamine infusions. STUDY DESIGN Randomized, blinded, prospective clinical trial. ANIMALS Fifty horses undergoing elective surgery. METHODS After acepromazine and flunixin meglumine premedication, horses received medetomidine (7 μg kg-1 ) intravenously (IV). Anaesthesia was induced with midazolam and racemic ketamine (Med treatment group; 2.2 mg kg-1 ; n = 25) or S-ketamine (S-ket treatment group; 1.1 mg kg-1 ; n = 25) IV and maintained with isoflurane in oxygen/air and medetomidine (Med; 3.5 μg kg-1 hour-1 ) or S-ketamine (S-ket; 0.5 mg kg-1 hour-1 ). All horses were mechanically ventilated. Cardiopulmonary variables were evaluated. Isoflurane end-tidal concentrations (Fe'Iso), dobutamine requirements and thiopental boli were recorded. Plasma samples were collected in six horses to evaluate S-ketamine and S-norketamine concentrations. After surgery, medetomidine 2 μg kg-1 was administered IV. Four independent observers scored recovery using a visual analogue scale and a numerical rating scale. RESULTS Both groups required similar mean Fe'Iso (1%). However, S-ket horses needed more thiopental boli. Median intraoperative cardiac index values were higher with S-ket (4.5 L minute-1 m-2 ) than Med (3.9 L minute-1 m-2 ). Overall, there were no differences in heart rate, blood pressure or dobutamine requirements; however, horses in S-ket showed higher heart rate values at 30 minutes after anaesthesia induction. Compared with Med horses, S-ket horses showed decreased PaO2 and increased pulmonary venous admixture values estimated with the Fshunt calculation. Recoveries were shorter and of poorer quality with S-ket. During infusion, S-ketamine and S-norketamine plasma concentrations lay in the ranges of 0.209-0.917 μg mL-1 and 0.250-0.723 μg mL-1 , respectively. CONCLUSIONS AND CLINICAL RELEVANCE Despite the higher intraoperative cardiac index with S-ket, both protocols were considered to provide acceptable cardiovascular function. However, recovery quality was significantly better in the Med group.
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Affiliation(s)
- M Paula Larenza Menzies
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Simone K Ringer
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Aude Conrot
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Regula Theurillat
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Berne, Berne, Switzerland
| | - Katharina Kluge
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Annette Pn Kutter
- Section of Anaesthesiology, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Michelle Jackson
- Clinic for Equine Surgery, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Wolfgang Thormann
- Clinical Pharmacology Laboratory, Institute for Infectious Diseases, University of Berne, Berne, Switzerland
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Theurillat R, Sandbaumhüter FA, Bettschart-Wolfensberger R, Thormann W. Microassay for ketamine and metabolites in plasma and serum based on enantioselective capillary electrophoresis with highly sulfated γ-cyclodextrin and electrokinetic analyte injection. Electrophoresis 2015; 37:1129-38. [DOI: 10.1002/elps.201500468] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 11/24/2015] [Accepted: 11/26/2015] [Indexed: 12/13/2022]
Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
| | | | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
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Clinical and pharmacokinetic evaluation of S-ketamine for intravenous general anaesthesia in horses undergoing field castration. Acta Vet Scand 2015; 57:21. [PMID: 25935721 PMCID: PMC4432908 DOI: 10.1186/s13028-015-0112-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 04/20/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Intravenous anaesthetic drugs are the primary means for producing general anaesthesia in equine practice. The ideal drug for intravenous anaesthesia has high reliability and pharmacokinetic properties indicating short elimination and lack of accumulation when administered for prolonged periods. Induction of general anaesthesia with racemic ketamine preceded by profound sedation has already an established place in the equine field anaesthesia. Due to potential advantages over racemic ketamine, S-ketamine has been employed in horses to induce general anaesthesia, but its optimal dose remains under investigation. The objective of this study was to evaluate whether 2.5 mg/kg S-ketamine could be used as a single intravenous bolus to provide short-term surgical anaesthesia in colts undergoing surgical castration, and to report its pharmacokinetic profile. RESULTS After premedication with romifidine and L-methadone, the combination of S-ketamine and diazepam allowed reaching surgical anaesthesia in the 28 colts. Induction of anaesthesia as well as recovery were good to excellent in the majority (n = 22 and 24, respectively) of the colts. Seven horses required additional administration of S-ketamine to prolong the duration of surgical anaesthesia. Redosing did not compromise recovery quality. Plasma concentration of S-ketamine decreased rapidly after administration, following a two-compartmental model, leading to the hypothesis of a consistent unchanged elimination of the parent compound into the urine beside its conversion to S-norketamine. The observed plasma concentrations of S-ketamine at the time of first movement were various and did not support the definition of a clear cut-off value to predict the termination of the drug effect. CONCLUSIONS The administration of 2.5 mg/kg IV S-ketamine after adequate premedication provided good quality of induction and recovery and a duration of action similar to what has been reported for racemic ketamine at the dose of 2.2 mg/kg. Until further investigations will be provided, close monitoring to adapt drug delivery is mandatory, particularly once the first 10 minutes after injection are elapsed. Taking into account rapid elimination of S-ketamine, significant inter-individual variability and rapid loss of effect over a narrow range of concentrations a sudden return of consciousness has to be foreseen.
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Canola PA, Valadão CA, Borges JHS, Canola JC. Evaluation of Cardiovascular Function During S(+)-Ketamine Constant Rate Infusion in Dorsally Recumbent Halothane-Anesthetized Horses. J Equine Vet Sci 2015. [DOI: 10.1016/j.jevs.2014.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Theurillat R, Larenza MP, Feige K, Bettschart- Wolfensberger R, Thormann W. Development of a method for analysis of ketamine and norketamine enantiomers in equine brain and cerebrospinal fluid by capillary electrophoresis. Electrophoresis 2014; 35:2863-9. [DOI: 10.1002/elps.201400093] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 04/07/2014] [Accepted: 04/21/2014] [Indexed: 11/06/2022]
Affiliation(s)
- Regula Theurillat
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
| | - M. Paula Larenza
- Equine Department; Vetsuisse Faculty; University of Zürich; Zürich Switzerland
| | - Karsten Feige
- Clinic for Horses; University of Veterinary Medicine; Hannover Germany
| | | | - Wolfgang Thormann
- Clinical Pharmacology Laboratory; University of Bern; Bern Switzerland
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Gozalo-Marcilla M, Gasthuys F, Schauvliege S. Partial intravenous anaesthesia in the horse: a review of intravenous agents used to supplement equine inhalation anaesthesia. Part 1: lidocaine and ketamine. Vet Anaesth Analg 2014; 41:335-45. [PMID: 24815750 DOI: 10.1111/vaa.12179] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 09/13/2013] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To review the literature with regard to the use of different intravenous agents as supplements to inhalational anaesthesia in horses. These drugs include lidocaine, ketamine, opioids and α2 -agonists. The Part 1 of this review will focus in the use of lidocaine and ketamine. DATABASES USED Pubmed & Web of Science. Search terms: horse, inhalant anaesthesia, balanced anaesthesia, partial intravenous anaesthesia, lidocaine, ketamine. CONCLUSIONS Different drugs and their combinations can be administered systemically in anaesthetized horses, with the aim of reducing the amount of the volatile agent whilst improving the recovery qualities and providing a multimodal analgesic approach. However, full studies as to whether these techniques improve cardiopulmonary status are not always available and potential disadvantages should also be considered.
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Affiliation(s)
- Miguel Gozalo-Marcilla
- Department of Surgery and Anaesthesia of Domestic Animals, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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19
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Peters L, Demmel S, Pusch G, Buters J, Thormann W, Zielinski J, Leeb T, Mevissen M, Schmitz A. Equine cytochrome P450 2B6 — Genomic identification, expression and functional characterization with ketamine. Toxicol Appl Pharmacol 2013; 266:101-8. [DOI: 10.1016/j.taap.2012.10.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 10/19/2012] [Accepted: 10/26/2012] [Indexed: 01/23/2023]
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20
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Gerritsmann H, Stalder GL, Seilern-Moy K, Knauer F, Walzer C. Comparison of S(+)-ketamine and ketamine, with medetomidine, for field anaesthesia in the European brown hare (Lepus europaeus). Vet Anaesth Analg 2012; 39:511-9. [PMID: 22788247 DOI: 10.1111/j.1467-2995.2012.00754.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To compare anaesthesia and recovery parameters of racemic ketamine or S(+)-ketamine in combination with medetomidine for intramuscular (IM) field anaesthesia in the European brown hare (EBH) (Lepus europaeus). STUDY DESIGN Randomized, prospective, blinded clinical trial. ANIMALS 20 adult EBH (eight male, 12 female), mean ± SD weight 3360 341). METHODS Medetomidine (0.2 mg kg(-1) ) and ketamine (30 mg kg(-1) ) (K-M group) or S(+)-ketamine (15 mg kg(-1) ) (S-M group) were administered by IM injection. Time until first effect and loss of righting reflex were recorded. During sedation and anaesthesia heart rate, saturation of arterial haemoglobin, respiratory rate, side stream end tidal CO(2) (Pe'CO(2) ), non invasive blood pressure, body temperature, cardiorespiratory parameters, palpebral reflex, jaw tone and nociception were recorded every 5 minutes. Medetomidine was antagonized with IM atipamezole (1 mg kg(-1) ) 45 minutes after treatment injection. Time until first head lift, standing and total recovery time (T-Recov) were recorded. Incidences of falling and involuntary movements during recovery were counted. Recovery quality was scored by visual analogue scale. Descriptive statistics were used to visualize maintenance data. All other data were included in multiple linear regression models. RESULTS Surgical anesthesia was not produced reliably with either protocol. Hypoxaemia occurred in both groups (SpO(2) < 90%). During recovery, falling was noted significantly less often (p < 0.001) in the S-M group (13 ± 7) versus the K-M group (27 ± 13). T-Recov was long, lasting for more than 3 hours in individuals with no significant differences between groups. CONCLUSION AND CLINICAL RELEVANCE S(+)-ketamine showed only minor advantages over racemic ketamine. Surgical anaesthesia was not achieved reliably with either protocol. Oxygen supplementation should be considered to prevent hypoxaemia. Further research is needed to develop an injectable field protocol adequate for surgical procedures, but with a rapid smooth recovery.
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Affiliation(s)
- Hanno Gerritsmann
- Research Institute of Wildlife Ecology, University of Veterinary Medicine, A-1160 Vienna, Austria.
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21
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Caslavska J, Thormann W. Stereoselective determination of drugs and metabolites in body fluids, tissues and microsomal preparations by capillary electrophoresis (2000–2010). J Chromatogr A 2011; 1218:588-601. [DOI: 10.1016/j.chroma.2010.08.072] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 08/20/2010] [Accepted: 08/25/2010] [Indexed: 10/19/2022]
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23
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Jud R, Picek S, Makara MA, Steininger K, Hässig M, Bettschart-Wolfensberger R. Comparison of racemic ketamine and S-ketamine as agents for the induction of anaesthesia in goats. Vet Anaesth Analg 2010; 37:511-8. [DOI: 10.1111/j.1467-2995.2010.00570.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Schmitz A, Thormann W, Moessner L, Theurillat R, Helmja K, Mevissen M. Enantioselective CE analysis of hepatic ketamine metabolism in different species in vitro. Electrophoresis 2010; 31:1506-16. [PMID: 20358543 DOI: 10.1002/elps.200900703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ketamine, an injectable anesthetic and analgesic consisting of a racemic mixture of S-and R-ketamine, is routinely used in veterinary and human medicine. Nevertheless, metabolism and pharmacokinetics of ketamine have not been characterized sufficiently in most animal species. An enantioselective CE assay for ketamine and its metabolites in microsomal preparations is described. Racemic ketamine was incubated with pooled microsomes from humans, horses and dogs over a 3 h time interval with frequent sample collection. CE data revealed that ketamine is metabolized enantioselectively to norketamine (NK), dehydronorketamine and three hydroxylated NK metabolites in all three species. The metabolic patterns formed differ in production rates of the metabolites and in stereoselectivity of the hydroxylated NK metabolites. In vitro pharmacokinetics of ketamine N-demethylation were established by incubating ten different concentrations of racemic ketamine and the single enantiomers of ketamine for 8 min and data modeling was based on Michaelis-Menten kinetics. These data revealed a reduced intrinsic clearance of the S-enantiomer in the racemic mixture compared with the single S-enantiomer in human microsomes, no difference in equine microsomes and the opposite effect in canine microsomes. The findings indicate species differences with possible relevance for the use of single S-ketamine versus racemic ketamine in the clinic.
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Affiliation(s)
- Andrea Schmitz
- Division of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Bern, Switzerland
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Portmann S, Kwan HY, Theurillat R, Schmitz A, Mevissen M, Thormann W. Enantioselective capillary electrophoresis for identification and characterization of human cytochrome P450 enzymes which metabolize ketamine and norketamine in vitro. J Chromatogr A 2010; 1217:7942-8. [PMID: 20609441 DOI: 10.1016/j.chroma.2010.06.028] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 05/31/2010] [Accepted: 06/10/2010] [Indexed: 10/19/2022]
Abstract
Ketamine, a phencyclidine derivative, is used for induction of anesthesia, as an anesthetic drug for short term surgical interventions and in subanesthetic doses for postoperative pain relief. Ketamine undergoes extensive hepatic first-pass metabolism. Enantioselective capillary electrophoresis with multiple isomer sulfated β-cyclodextrin as chiral selector was used to identify cytochrome P450 enzymes involved in hepatic ketamine and norketamine biotransformation in vitro. The N-demethylation of ketamine to norketamine and subsequently the biotransformation of norketamine to other metabolites were studied via analysis of alkaline extracts of in vitro incubations of racemic ketamine and racemic norketamine with nine recombinantly expressed human cytochrome P450 enzymes and human liver microsomes. Norketamine was formed by CYP3A4, CYP2C19, CYP2B6, CYP2A6, CYP2D6 and CYP2C9, whereas CYP2B6 and CYP2A6 were identified to be the only enzymes which enable the hydroxylation of norketamine. The latter two enzymes produced metabolic patterns similar to those found in incubations with human liver microsomes. The kinetic data of ketamine N-demethylation with CYP3A4 and CYP2B6 were best described with the Michaelis-Menten model and the Hill equation, respectively. This is the first study elucidating the individual enzymes responsible for hydroxylation of norketamine. The obtained data suggest that in vitro biotransformation of ketamine and norketamine is stereoselective.
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Affiliation(s)
- Simone Portmann
- Department of Clinical Pharmacology and Visceral Research, University of Bern, Murtenstrasse 35, CH-3010 Bern, Switzerland
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Larenza MP, Peterbauer C, Landoni MF, Levionnois OL, Schatzmann U, Spadavecchia C, Thormann W. Stereoselective pharmacokinetics of ketamine and norketamine after constant rate infusion of a subanesthetic dose of racemic ketamine or S-ketamine in Shetland ponies. Am J Vet Res 2009; 70:831-9. [PMID: 19566468 DOI: 10.2460/ajvr.70.7.831] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate pharmacokinetics of ketamine and norketamine enantiomers after constant rate infusion (CRI) of a subanesthetic dose of racemic ketamine or S-ketamine in ponies. ANIMALS Five 6-year-old Shetland pony geldings that weighed between 101 and 152 kg. PROCEDURES In a crossover study, each pony received a CRI of racemic ketamine (loading dose, 0.6 mg/kg; CRI, 0.02 mg/kg/min) and S-ketamine (loading dose, 0.3 mg/kg; CRI, 0.01 mg/kg/min), with a 1-month interval between treatments. Arterial blood samples were collected before and at 5, 15, 30, 45, and 60 minutes during drug administration and at 5, 10, 30, and 60 minutes after discontinuing the CRI. Plasma ketamine and norketamine enantiomers were quantified by use of capillary electrophoresis. Individual R-ketamine and S-ketamine concentration-versus-time curves were analyzed by use of a monocompartmental model. Plasma disposition curves for R-norketamine and S-norketamine were described by estimating the area under the concentration-versus-time curve (AUC), maximum concentration (Cmax), and time until Cmax. RESULTS Plasma concentrations of S-ketamine decreased and biodegradation products increased more rapidly after S-ketamine CRI, compared with results after racemic ketamine CRI. The R-norketamine was eliminated faster than was the S-norketamine. Significant differences between treatments were found for the AUC of S-ketamine and within the racemic ketamine CRI for the AUC and Cmax of norketamine isomers. CONCLUSIONS AND CLINICAL RELEVANCE CRI of S-ketamine may be preferable over CRI of racemic ketamine in standing equids because the S-enantiomer was eliminated faster when infused alone instead of as part of a racemic mixture.
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Affiliation(s)
- M Paula Larenza
- Anesthesiology Section, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bern CH-3001, Switzerland
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Schmitz A, Theurillat R, Lassahn PG, Mevissen M, Thormann W. CE provides evidence of the stereoselective hydroxylation of norketamine in equines. Electrophoresis 2009; 30:2912-21. [DOI: 10.1002/elps.200900221] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Capponi L, Schmitz A, Thormann W, Theurillat R, Mevissen M. In vitro evaluation of differences in phase 1 metabolism of ketamine and other analgesics among humans, horses, and dogs. Am J Vet Res 2009; 70:777-86. [DOI: 10.2460/ajvr.70.6.777] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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29
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Larenza MP, Ringer SK, Kutter APN, Conrot A, Theurillat R, Kummer M, Thormann W, Bettschart-Wolfensberger R. Evaluation of anesthesia recovery quality after low-dose racemic or S-ketamine infusions during anesthesia with isoflurane in horses. Am J Vet Res 2009; 70:710-8. [DOI: 10.2460/ajvr.70.6.710] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Schmitz A, Portier CJ, Thormann W, Theurillat R, Mevissen M. Stereoselective biotransformation of ketamine in equine liver and lung microsomes. J Vet Pharmacol Ther 2009; 31:446-55. [PMID: 19000264 DOI: 10.1111/j.1365-2885.2008.00972.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stereoselectivity has to be considered for pharmacodynamic and pharmacokinetic features of ketamine. Stereoselective biotransformation of ketamine was investigated in equine microsomes in vitro. Concentration curves were constructed over time, and enzyme activity was determined for different substrate concentrations using equine liver and lung microsomes. The concentrations of R/S-ketamine and R/S-norketamine were determined by enantioselective capillary electrophoresis. A two-phase model based on Hill kinetics was used to analyze the biotransformation of R/S-ketamine into R/S-norketamine and, in a second step, into R/S-downstream metabolites. In liver and lung microsomes, levels of R-ketamine exceeded those of S-ketamine at all time points and S-norketamine exceeded R-norketamine at time points below the maximum concentration. In liver and lung microsomes, significant differences in the enzyme velocity (V(max)) were observed between S- and R-norketamine formation and between V(max) of S-norketamine formation when S-ketamine was compared to S-ketamine of the racemate. Our investigations in microsomal reactions in vitro suggest that stereoselective ketamine biotransformation in horses occurs in the liver and the lung with a slower elimination of S-ketamine in the presence of R-ketamine. Scaling of the in vitro parameters to liver and lung organ clearances provided an excellent fit with previously published in vivo data and confirmed a lung first-pass effect.
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Affiliation(s)
- A Schmitz
- Division of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
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