The disposition and behavioral effects of methadone in Greyhounds
Version of Record online: 18 FEB 2008
© 2008 The Authors. Journal compilation © 2008 Association of Veterinary Anaesthetists
Veterinary Anaesthesia and Analgesia
Volume 35, Issue 3, pages 242–248, May 2008
How to Cite
KuKanich, B. and Borum, S. L. (2008), The disposition and behavioral effects of methadone in Greyhounds. Veterinary Anaesthesia and Analgesia, 35: 242–248. doi: 10.1111/j.1467-2995.2007.00369.x
- Issue online: 18 FEB 2008
- Version of Record online: 18 FEB 2008
- Received 12 December 2006; accepted 9 January 2007.
- volume of distribution
Objective To determine the behavioral effects and pharmacokinetics of methadone in healthy Greyhounds.
Study design Prospective experimental study.
Animals Three male and three female healthy Greyhounds.
Methods Methadone hydrochloride, 0.5 mg kg−1 IV (equivalent to 0.45 mg kg−1 methadone base), was administered as an IV bolus. Trained observers subjectively assessed the behavioral effects of methadone. Blood samples were obtained at predetermined time points and plasma methadone concentrations were measured by liquid chromatography with tandem mass spectrometry. Pharmacokinetic variables were estimated with computer software.
Results Methadone was well tolerated by the dogs with panting and defecation observed as adverse effects. Mild sedation was present, but no vomiting, excitement, or dysphoria was observed. The elimination half-life, volume of distribution, and plasma clearance were 1.53 ± 0.18 hours, 7.79 ± 1.87 L kg−1, and 56.04 ± 9.36 mL minute−1 kg−1, respectively.
Conclusions and clinical relevance Methadone was well tolerated by Greyhounds. The volume of distribution was larger than expected, with resultant lower plasma concentrations than expected. Higher doses may need to be administered to Greyhounds in comparison with non-Greyhound dogs in order to achieve similar plasma drug concentrations. A dosage of 1–1.5 mg kg−1 every 3–4 hours is suggested for future studies of analgesic efficacy of methadone in Greyhounds.