Dexmedetomidine hydrochloride is a widely used α2-adrenoreceptor agonist that causes sedation, analgesia, decreased anesthetic requirements, and cardiovascular depression in cats.1–3 The dextro enantiomer of medetomidine is responsible for the pharmacological activity of the racemic mixture; in most studies,4,5 the levo enantiomer appears inactive, at least at clinical doses. Therefore, as expected, equipotent doses of dexmedetomidine and medetomidine did not differ significantly with regard to subjective scores for sedation, analgesia, and muscle relaxation in cats.6,7
The mechanisms of action of the α2-adrenoreceptor agonists are related to the central activation of presynaptic α2-adrenoreceptors, which results in an inhibitory effect on noradrenaline release, and the stimulation of different postsynaptic, G-protein–coupled α2-adrenoreceptors, which result in peripheral vasoconstriction, analgesia and other effects.8 The initial increase in blood pressure caused by activation of peripheral α2-adrenoreceptors is temporary, and after the drug redistribution, this effect is balanced by the centrally mediated reduction in sympathetic activity.9,10
Reports of several studies1–3,6,7 of the use of dexmedetomidine in cats have been published. Similar to other α2-adrenoreceptor agonists, dexmedetomidine has been reported to decrease anesthetic requirements in some species, and therefore, it may be useful as an anesthetic adjunct.11–18 The pharmacokinetics of the drug in cats has not been reported, to our knowledge, thereby making recommendations on dosages and, in particular, dosing interval difficult. The purpose of the study reported here was to determine the pharmacokinetics of dexmedetomidine administered as a short-duration IV infusion in isoflurane-anesthetized cats.
Maximal plasma concentration
Minimum alveolar concentration
Apparent volume of distribution at steady state
Central Venous Catheterization set, Arrow International, Reading, Pa.
Dexdomitor, Pfizer, New York, NY.
Provided by the Orion Corp, Espoo, Finland.
Frontier BioPharm, Richmond, Ky.
TSQ Vantage, Thermo Scientific, San Jose, Calif.
LCQuan software, version 2.6, Thermo Scientific, San Jose, Calif.
Aria TLX-4, Thermo Fisher Scientific, Franklin, Mass.
ACE C18, Mac Mod, Chadds Ford, Pa.
High-performance liquid chromatography–grade acetonitrile, Burdick and Jackson, Muskegon, Mich.
Spectrophotometric grade formic acid, Sigma-Aldrich, St Louis, Mo.
High-performance liquid chromatography–grade acetic acid, Thermo Fisher Scientific, Franklin, Mass.
WinNonlin Pro, version 5.2, Pharsight, Cary, NC.
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