The effect of an alpha2-adrenoceptor antagonist on equine carbohydrate metabolism after intravenous glucose load

Vatinoxan is a peripherally acting alpha2-adrenoceptor antagonist used in veterinary medicine to attenuate the side effects of alpha2-adrenoceptor agonists. Vatinoxan also increases insulin response and reduces blood glucose (BG) after intravenous glucose in other species. The aim of this study was to investigate the effects of vatinoxan on BG and insulin concentration in horses after intravenous glucose. The design was an assessor-blind cross-over study. Nine horses were assigned to intravenous vatinoxan (0.2 mg/kg; VAT) or saline (SAL). Horses were administered an intravenous glucose bolus (150 mg/kg) immediately before each treatment. Blood samples were collected until 300 min. Differences between treatments were evaluated with repeated measures analysis of covariance. Change from baseline was used as a response. p < 0.05 was considered significant. After intravenous glucose, BG and insulin increased in all horses. VAT significantly reduced the increase in BG compared with SAL (p = 0.005). Although insulin increased initially significantly more after VAT at 15 min (median 45.7, min-max 20.7–61.6 µIU/mL) compared with SAL (p = 0.04; 28.3, 17.2–44.5 µIU/mL), there was no significant difference in the overall treatment effect. Peak insulin concentration occurred significantly earlier (p = 0.04) after VAT (median T_max 30, min-max 15–60 min) than SAL (median T_max 60, 15–60 min). In conclusion, vatinoxan induced an earlier insulin peak than saline and reduced BG increase after intravenous glucose load. Vatinoxan could potentially modify insulin secretion from the pancreas during hyperglycaemia, but more research is warranted.