The effect of verapamil on histamine and methacholine-induced bronchoconstriction.

Calcium antagonist, verapamil given by inhalation did not alter histamine bronchial hyper-reactivity in ten patients with extrinsic bronchial asthma and similarly did not modify methacholine-induced bronchoconstriction in further five patients. In eight non-asthmatic subjects verapamil reduced histamine sensitivity with increase in PC20H from 8.07(+/- 2.33) to 12.10(+/- 2.71, P less than 0.05) but failed to have an effect on methacholine sensitivity in five controls. The failure of inhaled verapamil to modify histamine and methacholine bronchial hyper-reactivity in asthmatic patients and the beneficial effect of calcium antagonists in exercise asthma suggests that these agents may act predominantly on the mast cell degranulation rather than the bronchial smooth muscle.