Action of 4-amino-α-[(tert-butylamino) methyl]-3, 5-dichlorobenzylalcohol hydrochloride (N-AB 365, clenbuterol) on the respiratory system

The bronchodilating effect and other related pharmacological properties of N-AB 365 were studied in comparison with those of isoproterenol, salbutamol and clorprenaline. N-AB 365 was found to produce a bronchodilating effect 1/20 ?? 1/100, 1/10 ?? 1/40 and was 2 to 5 times as strong as effects of isoproterenol, salbutamol and clorprenaline, respectively. The bronchodilating effect of N-AB 365 was sustained more than 10 times as long as those of isoproterenol and salbutamol, and in particular with oral administration, was much more potent. The bronchodilating effect of N-AB 365 seems to be due mainly to excitation of the adrenergic β2-receptor and partially to papaverine-like action. N-AB 365 showed an inhibitory effect on experimentally induced bronchial asthma by spraying of bronchoconstrictors and the effect by oral administration was much stronger than those of isoproterenol and salbutamol. N-AB 365 affected neither the volume output of respiratory tract fluid nor the tracheal ciliary movement with the doses around ED50 in bronchodilating action, however, it increased ciliary activity and decreased the volume output of respiratory tract fluid with large doses. Antitussive effect was also demonstrated only with the large doses. N-AB 365 induced a moderate decrease in blood pressure through vasodilatation but did not influence respiration. The effect of N-AB 365 on heart rate varied. There were cases of no change, slight increase or slight decrease in heart rate.