Present address: Department of Veterinary Clinics and Surgery, Faculdade de Ciências Agrárias e Veterinárias, São Paulo State University, Jaboticabal, SP 14884-900, Brazil.
Effect of dexmedetomidine on the minimum alveolar concentration of isoflurane in cats
Article first published online: 26 APR 2011
© 2011 Blackwell Publishing Ltd
Journal of Veterinary Pharmacology and Therapeutics
Volume 35, Issue 2, pages 163–168, April 2012
How to Cite
ESCOBAR, A., PYPENDOP, B. H., SIAO, K. T., STANLEY, S. D. and ILKIW, J. E. (2012), Effect of dexmedetomidine on the minimum alveolar concentration of isoflurane in cats. Journal of Veterinary Pharmacology and Therapeutics, 35: 163–168. doi: 10.1111/j.1365-2885.2011.01301.x
- Issue published online: 5 MAR 2012
- Article first published online: 26 APR 2011
- (Paper received 12 November 2010; accepted for publication 16 March 2011)
Escobar, A., Pypendop, B. H., Siao, K. T., Stanley, S. D., Ilkiw, J. E. Effect of dexmedetomidine on the minimum alveolar concentration of isoflurane in cats. J. vet. Pharmacol. Therap. 35, 163–168.
This study reports the effects of dexmedetomidine on the minimum alveolar concentration of isoflurane (MACiso) in cats. Six healthy adult female cats were used. MACiso and dexmedetomidine pharmacokinetics had previously been determined in each individual. Cats were anesthetized with isoflurane in oxygen. Dexmedetomidine was administered intravenously using target-controlled infusions to maintain plasma concentrations of 0.16, 0.31, 0.63, 1.25, 2.5, 5, 10, and 20 ng/mL. MACiso was determined in triplicate at each target plasma dexmedetomidine concentration. Blood samples were collected and analyzed for dexmedetomidine concentration. The following model was fitted to the concentration–effect data:
where MACiso.c is MACiso at plasma dexmedetomidine concentration C, MACiso.0 is MACiso in the absence of dexmedetomidine, Imax is the maximum possible reduction in MACiso, and IC50 is the plasma dexmedetomidine concentration producing 50% of Imax. Mean ± SE MACiso.0, determined in a previous study conducted under conditions identical to those in this study, was 2.07 ± 0.04. Weighted mean ± SE Imax, and IC50 estimated by the model were 1.76 ± 0.07%, and 1.05 ± 0.08 ng/mL, respectively. Dexmedetomidine decreased MACiso in a concentration-dependent manner. The lowest MACiso predicted by the model was 0.38 ± 0.08%, illustrating that dexmedetomidine alone is not expected to result in immobility in response to noxious stimulation in cats at any plasma concentration.