PhD Candidate The University of Queensland Gatton, Queensland, Australia
Abstract:
Background: Phenylbutazone is used for the management of hyperinsulinemia-associated laminitis; however, we have shown that it alters insulin and glucose dynamics of horses with insulin dysregulation (ID).
Hypothesis/
Objectives: Investigate the effect of phenylbutazone on insulin sensitivity in horses.
Animals: Seventeen University-owned adult horses including nine diagnosed with ID and eight controls.
Methods: In a randomised crossover design study with a 10-day washout period between treatments, horses received intravenous phenylbutazone (4.4 mg/kg SID) or placebo. On day eight of treatment, a modified frequently sampled intravenous glucose tolerance test (mFSIGTT) was performed. Insulin and glucose concentrations were measured with an IMMULITE1000 or a handheld glucometer respectively. Minimal model analysis was performed, and changes between treatments assessed with paired t-tests, with P < .05 considered significant.
Results: Phenylbutazone administration did not significantly alter insulin sensitivity in ID or control horses (P = .3280 and P = .3617, respectively) nor glucose effectiveness (P = .1187 and P = .2585, respectively). There was no significant effect on the acute insulin response to glucose in either group (P = .6723 and P = .5867). There was no significant effect on the areas under the curves for insulin (P = .4202 and P = .3171) or glucose (P = .6044 and P = .1321).
Conclusions and clinical importance: The changes in insulin and glucose dynamics observed after phenylbutazone administration in ID horses are not mediated by an alteration in insulin sensitivity. Further investigation into the unique mechanisms associated with phenylbutazone administration in ID horses is required.
