Pharmacokinetics and pharmacodynamics of intravenous dexmedetomidine in the horse

Abstract

The aim of the study was to describe the pharmacokinetics and selected pharmacodynamics of intravenous dexmedetomidine in horses. Eight adult horses received 5 μg/kg dexmedetomidine IV. Blood samples were collected before and for 10 h after drug administration to determine dexmedetomidine plasma concentrations. Pharmacokinetic parameters were calculated using noncompartmental analysis. Data from one outlier were excluded from the statistical summary. Behavioral and physiological responses were recorded before and for 6 h after dexmedetomidine administration. Dexmedetomidine concentrations decreased rapidly (elimination half-life of 8.03 ± 0.84 min). Time of last detection varied from 30 to 60 min. Bradycardia was noted at 4 and 10 min after drug administration (26 ± 8 and 29 ± 8 beats/min respectively). Head height decreased by 70% at 4 and 10 min and gradually returned to baseline. Ability to ambulate was decreased for 60 min following drug administration, and mechanical nociceptive threshold was increased during 30 min. Blood glucose peaked at 30 min (134 ± 24 mg/dL) and borborygmi were decreased for the first hour after dexmedetomidine administration. Dexmedetomidine was quickly eliminated as indicated by the rapid decrease in plasma concentrations. Physiological, behavioral, and analgesic effects observed after dexmedetomidine administration were of short duration.

Pharmacokinetic and pharmacodynamic analysis comparing diverse effects of detomidine, medetomidine, and dexmedetomidine in the horse: a population analysis

“…The HR and HH measurements were obtained at baseline and at 4, 10, 20, 30, 45 min and 1, 1.5, 2 and 3 h postdosing. More detailed methods of these studies including analytical techniques and other physiological and behavioral measurements were published (Grimsrud et al ., , ; Mama et al ., ; Rezende et al ., ).…”

Is there a place for dexmedetomidine in equine anaesthesia and analgesia? A systematic review (2005–2017)

“…Mean (± SD ) half‐lives of dexmedetomidine following an i.v. bolus in young and adult ponies were 19.8 ± 9.63 and 28.96 ± 7.61 min, respectively, (Bettschart‐Wolfensberger et al., ) and in horses was shorter, 8.03 ± 0.84 min (Rezende et al., ). After CRI termination, Ranheim et al.…”

“…Rezende, Grimsrud, Stanley, Steffey, and Mama () also considered a noncompartmental analysis to describe the PK of a 5 μg/kg i.v. bolus, by means of liquid chromatography–mass spectrometry (LC‐MS).…”

“…Cardiac output (CO) was obtained by the thermal dilution technique to calculate CI and SVRI. Rezende, Grimsrud, Stanley, Steffey, and Mama (2015) also considered a noncompartmental analysis to describe the PK of a 5 μg/ kg i.v. bolus, by means of liquid chromatography-mass spectrometry (LC-MS).…”

“…When comparing the different PK studies of dexmedetomidine, it is difficult to draw a conclusion, mainly due to the different methodologies used, and also the absence of articles directly comparing its effects with those of other α 2 -agonists. Most authors used noncompartmental analysis (Bettschart-Wolfensberger et al, 2005;Ranheim et al, 2015;Rezende et al, 2015). The most interesting finding was the rapid drug elimination.…”