Effects of midodrine on blood flow in dog vascular beds

Effects of alpha-(2,5-dimethoxyphenyl)-beta-glycinamide-ethanol hydrochloride (midodrine, ST-1085) on blood flow in different vascular beds were examined in anesthetized dogs. Intravenously administered midodrine at doses of 0.3 and 0.6 mg/kg induced a transient increase followed by a long-lasting decrease in femoral arterial blood flow. Renal arterial blood flow exhibited an initial decrease followed by returning toward the control level, and thereafter decreased again. Vertebral, common carotid, superior mesenteric and coronary arterial blood flow, and cardiac output gradually decreased. Midodrine did not have any effects on cerebral tissue blood flow. The changes were more remarkable at a dose of 0.6 mg/kg than at 0.3 mg/kg. Each arterial blood flow change was statistically analyzed 20, 30 and 60 min after the administration of 0.6 mg/kg of midodrine. The decrease of coronary arterial blood flow by the treatment with midodrine was significantly smaller than those of superior mesenteric and femoral arterial blood flow at 20 and 30 min after midodrine administration. The decrease of renal arterial blood flow was significantly smaller than those of superior mesenteric arterial blood flow at 20 and 30 min, and femoral arterial blood flow at 20, 30 and 60 min after the administration. The decrease of vertebral arterial blood flow was also smaller than that of femoral arterial blood flow at 20, 30 and 60 min after the administration.