[Pharmacological action of SN-408, a novel long-acting selective beta 2-adrenoceptor agonist]

The bronchodilating effect and other related pharmacological properties of SN-408 were studied in comparison with those of isoproterenol, salbutamol and procaterol. SN-408 caused concentration-dependent relaxation of isolated guinea pig trachea via the beta 2-adrenoceptor. The order of relaxation potency was: procaterol greater than SN-408 greater than or equal to isoproterenol greater than salbutamol, but the duration of the action of SN-408 was far longer than those of other beta-agonists. Positive chronotropic and inotropic actions of SN-408 in isolated guinea pig right atria and left atria were less potent than those of other beta-agonists. In isolated guinea pig lung tissues, SN-408 increased cyclic AMP contents. Also in vivo, SN-408 showed dose-dependent bronchodilating action by i.v. administration in anesthetized guinea pigs and by inhalation in conscious guinea pigs. Bronchodilating actions of SN-408 were less potent than those of procaterol and isoproterenol, but the duration of action of SN-408 was far longer than those of other beta-agonists. SN-408 showed no evidence of the development of tolerance to the bronchodilating action. SN-408 caused small tachycardia in guinea pigs by i.v. and inhalation. SN-408 given i.v. suppressed vascular permeability in mice. These results indicate that SN-408 is a long-acting and selective beta 2-stimulant bronchodilator.