Abstract
Objectives
To investigate the effects of MK‐467 on sedation quality, and cardiopulmonary and
pharmacokinetic variables in horses sedated intravenously (IV) with romifidine.
Study design
Experimental, randomized, crossover design.
Animals
Seven healthy mares.
Methods
Romifidine (80 μg kg−1; R) and MK‐467 (200 μg kg−1; MK) were administered IV alone and in combination (R + MK). Levels of sedation and
borborygmi were scored. Heart rate (HR), direct arterial blood pressure (ABP) and
respiratory rate (fR) were recorded. Arterial and venous blood gas analyses were performed and venous
plasma drug concentrations were measured. Pharmacokinetic parameters were calculated.
Linear mixed modelling for repeated measures, contrasts of least square means by Bonferroni
correction tests, one‐way anova for repeated measures with Bonferroni multiple comparison tests and paired Student's
t‐tests were used to compare results within and between treatments as appropriate.
Significance was set at p < 0.05.
Results
After R, ABP increased and HR and fR decreased significantly. After R + MK, HR, fR, systolic and mean ABP decreased. MK alone increased both HR and fR. After R, ABP was significantly higher than after R + MK. HR and fR were significantly higher after MK than after R and R + MK. Areas under the curve
for sedation time were similar after R and R + MK. Intestinal activity decreased markedly
after R and less after R + MK. Volume of distribution and clearance of romifidine
were significantly higher and area under the concentration time curve extrapolated
to infinity significantly lower after R + MK than after R.
Conclusions
Combined romifidine and MK‐467 prevented the cardiovascular changes commonly seen
with romifidine but did not affect sedation quality.
Clinical relevance
Combined IV romifidine and MK‐467 can be used to attenuate the cardiovascular effects
of romifidine, such as in horses with colic or undergoing general anaesthesia.
Keywords
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Article info
Publication history
Accepted:
November 24,
2015
Received:
September 21,
2015
Identification
Copyright
© 2016 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Inc. All rights reserved.
