Effects of Epinephrine, Detomidine, and Butorphanol on Assessments of Insulin Sensitivity in Mares.
Authors: Kerrigan Lauren E, Thompson Donald L, Chapman Ann M, Oberhaus Erin L
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Reliable assessment of insulin sensitivity in horses presents a practical challenge when animals are fractious, as the stress response itself can confound results. Kerrigan et al. (2020) investigated how three common pharmaceutical agents—epinephrine, detomidine, and butorphanol—affect two key insulin sensitivity tests: insulin response to glucose (IR2G) and glucose response to insulin (GR2I). Through a series of controlled experiments using mares, the researchers administered these drugs at clinical doses before performing standardised glucose and insulin challenges, measuring insulin and glucose concentrations over 30 minutes. Epinephrine dramatically suppressed insulin secretion during the first 15 minutes following glucose challenge (P < 0.05), whilst detomidine and its combination with butorphanol produced severe, sustained suppression of IR2G (P < 0.0001); however, neither sedative altered resting glucose concentrations or GR2I responses. These findings have important implications: alpha-2 agonists like detomidine can be safely used to sedate fractious mares during insulin challenge testing without compromising the validity of GR2I results, but their use before glucose challenge tests renders IR2G data unreliable. Practitioners should therefore choose their testing protocol according to sedation requirements, reserving IR2G assessments for co-operative animals or using detomidine only when GR2I testing is the diagnostic priority.
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Practical Takeaways
- •Do not use epinephrine-releasing sedatives (sympathoadrenal stimulants) when conducting insulin sensitivity tests on mares, as they will invalidate results by suppressing insulin response to glucose
- •Detomidine alone or combined with butorphanol can be safely used for sedating fractious horses during glucose-to-insulin response testing, as it does not interfere with this assessment
- •Consider the pharmacological effects of sedatives on endocrine testing protocols—drug selection matters significantly for accurate metabolic evaluations in equine practice
Key Findings
- •Epinephrine (5 µg/kg BW) suppressed insulin response to glucose (IR2G) at 5-15 minutes compared to controls (P < 0.05)
- •Detomidine and detomidine/butorphanol severely suppressed IR2G (P < 0.0001) but did not alter glucose response to insulin (GR2I)
- •Butorphanol alone had no effect on IR2G, and sedation did not affect resting glucose concentrations
- •Detomidine may be useful for conducting insulin sensitivity tests in fractious horses due to lack of effect on GR2I, while adrenergic agonists cannot be used for this purpose