Role of calcium channel blocking agents in the treatment of allergic asthma

Effects of different dosages of the calcium antagonist verapamil in exercise- and methacholine-induced bronchospasm in children with chronic asthma

The protective effect of 5 mg/2 ml and 10 mg/4 ml of the calcium antagonist verapamil on methacholine challenge and exercise were evaluated in two groups of asthmatic children. Saline solution was used as placebo. No significant differences were seen in baseline pulmonary function in and within groups. There was a minimal but significant bronchodilation 30 minutes after inhalation of verapamil 5 mg/2 ml. The drug did not reduce methacholine sensitivity at any dosage. After exercise, verapamil 5 mg/2 ml showed a significant change in the maximum percentage drop in forced expiratory volume in 1 second (FEV1) compared with placebo. This was not the case for the group treated with a double dosage. At this time, there is no evidence for a major role of verapamil in the treatment of childhood asthma.

Calcium channel blocking agents in bronchial hyperreactivity

A variety of clinical and animal bronchial challenge experiments have been undertaken to assess the efficacy and sites of action of the calcium channel blockers nifedipine and verapamil in blunting bronchoconstriction. Nifedipine appears to be the more effective of these agents, and it blunts the airways response to methacholine and histamine inhalation as well as the bronchoconstriction caused by exercise or cold air hyperpnea. The mechanism by which it acts is difficult to define with certainty because of the widely distributed role of calcium ion within the bronchoconstriction pathways, but nifedipine appears to exert a direct effect on airway wall smooth muscle as well as a possible influence on mast cell mediator release.