The effects of an alpha-2-adrenoceptor agonist, antagonist, and their combination on the blood insulin, glucose, and glucagon concentrations in insulin sensitive and dysregulated horses.

Alpha-2-adrenoceptor agonists are sedatives that can cause fluctuations in serum insulin and blood glucose (BG) concentrations in horses. The objectives of this study were to investigate the effects of detomidine and vatinoxan on BG, insulin, and glucagon concentrations in horses with and without insulin dysregulation (ID). In a blinded cross-over design, eight horses with ID and eight horses without ID were assigned to each of four treatments: detomidine (0.02 mg/kg; DET), vatinoxan (0.2 mg/kg; VAT), detomidine + vatinoxan (DET + VAT), and saline control (SAL). Blood samples were taken at 0, 1, 2, 4, 6, and 8 h. Change from baseline was used as the response in modelling, and the differences between treatments were evaluated with repeated measures analysis of covariance. P values ≤0.05 were considered significant. Comparing DET vs. SAL and DET vs. DET + VAT, insulin was higher at 2 h in the non-ID group and 2 and 4 h in the ID group. There was no difference in insulin between SAL and DET + VAT or VAT. Comparing DET vs. SAL, BG was higher at 1 and 2 h then was lower at 4 h in both ID and non-ID groups. At 1 h in both groups, BG after DET + VAT was lower than after DET but higher than after SAL. Comparing DET vs. SAL, glucagon was lower at 1 h in the ID group and 1 and 2 h in the non-ID group. Vatinoxan was effective in preventing detomidine-induced hyperglycaemia as well as the subsequent insulin increase in horses with ID.