Pirbuterol, a selecttve beta2 adrenergic bronchodilator.

Pirbuterol, 2-hydroxymethyl-3-hydroxy-6-(1-hydroxy-2-tert-butylaminoethyl)pyridine, is a new beta2 adrenergic agonist bronchodilator. Comparison of the relative potencies of pirbuterol, salbutamol and isoproterenol as relaxants of isolated guinea-pig tracheal muscle and as positive chronotropic agents in isolated guinea-pig atria indicate that the relative selectivity of pirbuterol for pulmonary as opposed to cardiac tissue is 9 times greater than that for salbutamol and some 1500 times greater than that for isoproterenol. Pirbuterol is effective by the oral, intravenous and inhalation routes of administration. In conscious guinea pigs, pirbuterol antagonizes both histamine- and acetylcholine-induced bronchoconstriction and "microshock" anaphylaxis; combinations of pirbuterol and theophylline cause additive effects against histamine-induced bronchoconstriction. In conscious dogs, the cardiovascular effects of pirbuterol are clearly distinguished from those of salbutamol, in that salbutamol causes a more pronounced tachycardia. In anesthetized dogs the cardiovascular effects of pirbuterol and salbutamol are comparable; they are less potent than isoproterenol and have less pronounced although longer lasting effects.