Effect of calcium antagonists in experimental asthma.

Verapamil was found to be an effective inhibitor of isometric tension in in vitro, experimental anaphylaxis in guinea pig trachealis smooth muscle. The mean IC50 for protection studies was 2 X 10(-4) M; the drug was also effective as a bronchoreversal agent. The inhibitory effect of verapamil upon the initial rate of isometric muscle tension suggests an action beyond simple calcium channel inhibition. No inhibition of tracheal mast cell histamine release was observed. Verapamil was slightly more potent than theophylline in this in vitro anaphylactic model.