Pharmacological effects of urapidil on bronchospasm, myocardial hypoxia and postural hypotension in experimental animals.

We studied the effects of urapidil on bronchospasm, myocardial hypoxia and postural hypotension in experimental animals. Urapidil dose-dependently inhibited bronchospasm induced by histamine in anaesthetized guinea pigs and the contraction of isolated trachea induced by noradrenaline or phenylephrine. Urapidil markedly delayed the appearance of severe dyspnoea induced by histamine aerosol in guinea pigs. Further, urapidil inhibited isoproterenol-induced ST depression in rats and inhibited histamine-induced ST depression in rabbits. The postural hypotension induced by prazosin was greater than that induced by urapidil in equihypotensive doses in conscious rabbits. Urapidil induced a lesser alpha-blockade in the vein than in the artery compared with prazosin. These combined properties of urapidil suggest that the drug is worth investigation in hypertensive patients with bronchial asthma or ischaemic heart disease.