The effect of verapamil on histamine and methacholine‐induced bronchoconstriction

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Abstract
Ca antagonist, verapamil, given by inhalation did not alter histamine bronchial hyper-reactivity in 10 patients with extrinsic bronchial asthma and similarly did not modify methacholine-induced bronchoconstriction in 5 patients. In 8 non-asthmatic subjects verapamil reduced histamine sensitivity with increase in PC20H from 8.07(.+-.2.33)-12.10(.+-.2.71, P < 0.05) but failed to have an effect on methacholine sensitivity in 5 controls. The failure of inhaled verapamil to modify histamine and methacholine bronchial hyper-reactivity in asthmatic patients and the beneficial effect of Ca antagonists in exercise asthma suggests that these agents may act predominantly on the mast cell degranulation rather than the bronchial smooth muscle.