The effect of thymoxamine and cromolyn sodium on postexercise bronchoconstriction in asthma.

Of the 22 patients with extrinsic bronchial asthma, 13 patients developed post-exercise bronchoconstriction after treadmill exercise, whereas in 9 patients treadmill exercise had no effect on the ventilatory capacity. No statistical difference in the resting lung volumes and CO transfer factor was found between the two groups. A significant inhibition of postexercise bronchoconstriction was observed in 12 of 13 patients following thymoxamine or cromolyn sodium inhalation. Inhibition of postexercise bronchoconstriction by alpha blockade with thymoxamine suggests that increased alpha adrenergic activity in the presence of diminished beta receptor responsiveness to catecholamines, norepinephrine released during exercise could have a marked alpha agonistic effect giving rise to bronchoconstriction. It has been suggested that cromolyn sodium has a cyclic phosphodiesterase inhibiting action. This might increase levels of AMP and restore the beta receptor responsiveness to catecholamines.