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Journal of veterinary pharmacology and therapeutics2020; 43(4); 369-376; doi: 10.1111/jvp.12855

Pharmacokinetics and clinical effects of xylazine and dexmedetomidine in horses recovering from isoflurane anesthesia.

Abstract: This study determined the pharmacokinetics and compared the clinical effects of xylazine and dexmedetomidine in horses recovering from isoflurane anesthesia. Six healthy horses aged 8.5 ± 3 years and weighing 462 ± 50 kg were anesthetized with isoflurane for 2 hr under standard conditions on two occasions one-week apart. In recovery, horses received 200 μg/kg xylazine or 0.875 μg/kg dexmedetomidine intravenously and were allowed to recover without assistance. These doses were selected because they have been used for postanesthetic sedation in clinical and research studies. Serial venous blood samples were collected for quantification of xylazine and dexmedetomidine, and the pharmacokinetic parameters were calculated. Two individuals blinded to treatment identity evaluated recovery quality with a visual analog scale. Times to stand were recorded. Results (mean ± SD) were compared using paired t tests or Wilcoxon signed-ranked test with p < .05 considered significant. Elimination half-lives (62.7 ± 21.8 and 30.1 ± 8 min for xylazine and dexmedetomidine, respectively) and steady-state volumes of distribution (215 ± 123 and 744 ± 403 ml/kg) were significantly different between xylazine and dexmedetomidine, whereas clearances (21.1 ± 17.3 and 48.6 ± 28.1 ml/minute/kg), times to stand (47 ± 24 and 53 ± 12 min) and recovery quality (51 ± 24 and 61 ± 22 mm VAS) were not significantly different. When used for postanesthetic sedation following isoflurane anesthesia in healthy horses, dexmedetomidine displays faster plasma kinetics but is not associated with faster recoveries compared to xylazine.
© 2020 John Wiley & Sons Ltd.
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Publication Date: 2020-03-12 PubMed ID: 32166760DOI: 10.1111/jvp.12855Google Scholar: Lookup
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  • Journal Article
  • Randomized Controlled Trial
  • Veterinary

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article focuses on a comparative study of the pharmacokinetics and clinical effects of two anaesthetic drugs in horses: xylazine and dexmedetomidine. These drugs were administered to horses recovering from isoflurane anaesthesia, with the aim to understand their effects on recovery periods, how the body processes these drugs, and any significant differences between them.

Study Design

  • The research was conducted on six healthy horses, each around eight and a half years old and with an average weight of 462 kg.
  • Each horse was anesthetized with isoflurane for two hours under standard conditions on two separate occasions, with a gap of a week in between.
  • During recovery from anesthesia, the horses were injected with either 200 μg/kg xylazine or 0.875 μg/kg dexmedetomidine, doses chosen based on prior usage in postanesthetic sedation studies.
  • The horses were left to recover without assistance, and venous blood samples were systematically collected to ascertain the concentration of xylazine and dexmedetomidine present overtime.
  • Pharmacokinetic parameters, such as elimination half-lives and steady-state volumes of distribution, were calculated for both drugs based on these blood sample data.
  • Lastly, recovery quality was assessed by using a visual analog scale by two individuals who were unaware of the treatment given to each horse.

Results and Findings

  • The research found significant differences between xylazine and dexmedetomidine on certain parameters. Dexmedetomidine had a faster elimination half-life (30.1±8 minutes) and larger volume of distribution (744±403 ml/kg) than xylazine (62.7±21.8 minutes and 215±123 ml/kg, respectively).
  • However, other parameters such as clearances, times to stand, and recovery quality assessment showed no significant difference between the two drugs.
  • The research concludes that while dexmedetomidine has faster plasma kinetics, it does not necessarily contribute to faster recovery periods compared to xylazine post-isoflurane anesthesia in healthy horses.

Cite This Article

APA
Guedes A, Knych H, Tucker L, Almeida DC, Baldo CF, Wendt-Hornickle E, Allweiler S. (2020). Pharmacokinetics and clinical effects of xylazine and dexmedetomidine in horses recovering from isoflurane anesthesia. J Vet Pharmacol Ther, 43(4), 369-376. https://doi.org/10.1111/jvp.12855

Publication

Journal of veterinary pharmacology and therapeutics
ISSN: 1365-2885
NlmUniqueID: 7910920
Country: England
Language: English
Volume: 43
Issue: 4
Pages: 369-376

Researcher Affiliations

Guedes, Alonso
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Minneapolis, MN, USA.
Knych, Heather
  • K. L. Maddy Equine Analytical Chemistry Laboratory, School of Veterinary Medicine, University of California, Davis, CA, USA.
Tucker, Laura
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Minneapolis, MN, USA.
Almeida, Daniel C
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Minneapolis, MN, USA.
Baldo, Caroline F
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Minneapolis, MN, USA.
Wendt-Hornickle, Erin
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Minneapolis, MN, USA.
Allweiler, Sandra
  • Veterinary Clinical Sciences Department, College of Veterinary Medicine, University of Minnesota, Minneapolis, MN, USA.

MeSH Terms

  • Analgesics / administration & dosage
  • Analgesics / pharmacokinetics
  • Analgesics / pharmacology
  • Anesthesia Recovery Period
  • Anesthetics, Inhalation / administration & dosage
  • Anesthetics, Inhalation / pharmacokinetics
  • Anesthetics, Inhalation / pharmacology
  • Animals
  • Cross-Over Studies
  • Dexmedetomidine / administration & dosage
  • Dexmedetomidine / pharmacokinetics
  • Dexmedetomidine / pharmacology
  • Female
  • Horses / blood
  • Hypnotics and Sedatives / administration & dosage
  • Hypnotics and Sedatives / pharmacokinetics
  • Isoflurane / pharmacology
  • Male
  • Xylazine / administration & dosage
  • Xylazine / pharmacokinetics
  • Xylazine / pharmacology

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Citations

This article has been cited 5 times.
  1. Tucker L, Almeida D, Wendt-Hornickle E, Baldo CF, Allweiler S, Guedes AGP. Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses. Animals (Basel) 2022 Feb 1;12(3).
    doi: 10.3390/ani12030353pubmed: 35158676google scholar: lookup
  2. Cunneen A, Pratt S, Perkins N, McEwen M, Truchetti G, Rainger J, Farry T, Kidd L, Goodwin W. Total Intravenous Anaesthesia with Ketamine, Medetomidine and Midazolam as Part of a Balanced Anaesthesia Technique in Horses Undergoing Castration. Vet Sci 2021 Jul 26;8(8).
    doi: 10.3390/vetsci8080142pubmed: 34437464google scholar: lookup
  3. Gozalo-Marcilla M, Ringer SK. Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature. Animals (Basel) 2021 Jun 14;11(6).
    doi: 10.3390/ani11061777pubmed: 34198637google scholar: lookup
  4. Di Cesare F, Rabbogliatti V, Draghi S, Amari M, Brioschi FA, Villa R, Ravasio G, Cagnardi P. Pharmacokinetics of dexmedetomidine in anaesthetized horses following repeated subcutaneous administration and intravenous constant rate infusion. BMC Vet Res 2023 Dec 9;19(1):264.
    doi: 10.1186/s12917-023-03831-wpubmed: 38071301google scholar: lookup
  5. Ruíz-López P, Cuypers C, Schauvliege S. Xylazine Infusion during Equine Colic Anesthesia with Isoflurane and Lidocaine: A Retrospective Study. Animals (Basel) 2023 Sep 13;13(18).
    doi: 10.3390/ani13182902pubmed: 37760302google scholar: lookup
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