Plasma pharmacokinetics and pharmacodynamics of alfaxalone in neonatal foals after an intravenous bolus of alfaxalone following premedication with butorphanol tartrate

Goodwin, Wendy, Keates, Helen, Pasloske, Kirby, Pearson, Martin, Sauer, Ben and Ranasinghe, Millagahamada G. (2012) Plasma pharmacokinetics and pharmacodynamics of alfaxalone in neonatal foals after an intravenous bolus of alfaxalone following premedication with butorphanol tartrate. Veterinary Anaesthesia and Analgesia, 39 5: 503-510. doi:10.1111/j.1467-2995.2012.00734.x


Author Goodwin, Wendy
Keates, Helen
Pasloske, Kirby
Pearson, Martin
Sauer, Ben
Ranasinghe, Millagahamada G.
Title Plasma pharmacokinetics and pharmacodynamics of alfaxalone in neonatal foals after an intravenous bolus of alfaxalone following premedication with butorphanol tartrate
Journal name Veterinary Anaesthesia and Analgesia   Check publisher's open access policy
ISSN 1467-2987
1467-2995
Publication date 2012-05-30
Sub-type Article (original research)
DOI 10.1111/j.1467-2995.2012.00734.x
Volume 39
Issue 5
Start page 503
End page 510
Total pages 8
Place of publication Oxford, United Kingdom
Publisher Wiley-Blackwell Publishing
Collection year 2013
Language eng
Formatted abstract
Objective  To determine the pharmacokinetics and pharmacodynamics of the neurosteroid anaesthetic, alfaxalone, in neonatal foals after a single intravenous (IV) injection of alfaxalone following premedication with butorphanol tartrate.

Study design
  Prospective experimental study.

Animals 
Five clinically healthy Australian Stock Horse foals of mean ± SD age of 12 ± 3 days and weighing 67.3 ± 12.4 kg.

Methods
  Foals were premedicated with butorphanol (0.05 mg kg−1 IV) and anaesthesia was induced 10 minutes later by IV injection with alfaxalone 3 mg kg−1. Cardiorespiratory variables (pulse rate, respiratory rate, direct arterial blood pressure, arterial blood gases) and clinical signs of anaesthetic depth were evaluated throughout anaesthesia. Venous blood samples were collected at strategic time points and alfaxalone plasma concentrations were assayed using liquid chromatography-mass spectrometry (LC/MS) and analysed by noncompartmental pharmacokinetic analysis.

Results
  The harmonic, mean ± SD plasma elimination half life (t½) for alfaxalone was 22.8 ± 5.2 minutes. The observed mean plasma clearance (Clp) and volume of distribution (Vd) were 19.9 ± 5.9 mL minute kg−1 and 0.6 ± 0.2 L kg−1, respectively. Overall, the quality of the anaesthetic inductions and recoveries was good and most monitored physiological variables were clinically acceptable in all foals, although some foals became hypoxaemic for a short period following recumbency. The mean durations of anaesthesia from induction to first movement and from induction to standing were 18.7 ± 7 and 37.2 ± 4.7 minutes, respectively.

Conclusions  The anaesthetic protocol used provided a predictable and consistent plane of anaesthesia in the five foals studied, with minimal cardiovascular depression. In foals, as in the adult horse, alfaxalone has a short elimination half life.

Clinical relevance
  Alfaxalone appears to be an adequate anaesthetic induction agent in foals and the pharmacokinetics suggest that, with continuous infusion, it might be suitable to provide more prolonged anaesthesia. Oxygen supplementation is recommended.
Keyword Alfaxalone
Anaesthesia
Foal
Pharmacodynamics
Pharmacokinetics
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Early view: First published online: 30 MAY 2012

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Veterinary Science Publications
 
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Created: Wed, 25 Jul 2012, 11:00:45 EST by Annette Winter on behalf of School of Veterinary Science