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The pharmacokinetics of dexmedetomidine administered as a constant rate infusion in horses
Author(s) -
Ranheim B.,
Risberg Å. I.,
Spadavecchia C.,
Landsem R.,
Haga H. A.
Publication year - 2015
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/jvp.12157
Subject(s) - dexmedetomidine , sedation , pharmacokinetics , volume of distribution , anesthesia , sedative , medicine , elimination rate constant , medetomidine , pharmacology , heart rate , blood pressure
Dexmedetomidine, the most selective α 2 ‐adrenoceptor agonist in clinical use, is increasingly being used in both conscious and anaesthetized horses; however, the pharmacokinetics and sedative effects of this drug administered alone as an infusion are not previously described in horses. Seven horses received an infusion of 8 μ g dexmedetomidine/kg/h for 150 min, venous blood samples were collected, and dexmedetomidine concentrations were assayed using liquid chromatography‐mass spectrometry ( LC / MS ) and analyzed using noncompartmental pharmacokinetic analysis. Sedation was scored as the distance from the lower lip of the horse to the ground measured in centimetre. The harmonic mean ( SD ) plasma elimination half‐life (Lambda z half‐life) for dexmedetomidine was 20.9 (5.1) min, clearance (Cl) was 0.3 (0.20) L/min/kg, and volume of distribution at steady‐state ( Vd ss ) was 13.7 (7.9) L/kg. There was a considerable individual variation in the concentration of dexmedetomidine vs. time profile. The level of sedation covaried with the plasma concentration of dexmedetomidine. This implies that for clinical use of dexmedetomidine constant rate infusion in conscious horses, infusion rates can be easily adjusted to effect, and this is preferable to an infusion at a predetermined value.