Acute effects of the alpha(2)-adrenoreceptor antagonist idazoxan on hormonal responses and symptoms of hypoglycaemia in patients with type 1 diabetes mellitus

The aim of the present study was to evaluate the effect of the alpha(2)-adrenoceptor antagonist idazoxan on hormonal responses and hypoglycaemia symptoms in patients with insulin-dependent (Type 1) diabetes mellitus. Six male Type 1 diabetic patients were studied with and without intravenous infusion of idazoxan. Hypoglycaemia was induced by an intravenous infusion of insulin (100 mU.kg(-1).h(-1)), together with a glucose clamp, to obtain an arterialised venous blood glucose level of 2.3 mmol/l. Idazoxan was given at a dose of 295 mu g/kg. Venous blood samples were obtained for analyses of free insulin, growth hormone (GH), glucagon and catecholamines. Symptoms were scored on a visual-analogue rating scale. Areas under the curves with and without idazoxan were respectively 22.4+/-7.0 vs 33.0+/-9.6 mu g.l(-1).h (p = 0.17) for GH, 4.1+/-1.1 vs 2.4+/-0.9 nmol.l(-1).h (p < 0.05) for adrenaline, 5.6+/-0.9 vs 1.3+/-0.5 nmol.l(-1).h (p < 0.05) for noradrenaline and 51+/-38 vs -40+/-11 ng.l(-1).h (p < 0.05) for glucagon. Sweating and palpitations were more pronounced during idazoxan infusion than during the control test. It is concluded that idazoxan increases catecholamine and glucagon responses as well as some of the warning signals of hypoglycaemia in Type 1 diabetic patients, whereas the GH response seems less affected by idazoxan.