Calcium channel blocking agents in the prophylaxis of asthma.

Asthma is a state of reversible airway obstruction caused by the activation and response of different cell types (smooth muscle cells, mast cells, mucous gland secretory cells, and inflammatory cells) in various combinations. Recent evidence has demonstrated that all these cells require calcium-dependent reactions for their activation, which suggests that mobilization of calcium from extracellular and intraorganelle storage depots to the cytoplasmic matrix may be one possible underlying mechanism for asthma. Numerous agents have been developed to prevent this flow of calcium to the intracellular cytoplasmic matrix. Although their exact mechanism of action is not always clear, it has been shown that they can be effective in preventing muscle spasm and release of chemical mediators from mast cells following antigen and exercise challenges. Studies indicate that one calcium channel blocking agent, ketitofen, is effective as a prophylactic agent in the treatment of mild to moderate asthma. Other calcium channel blockers, including nifedipine, verapamil, and diltiazem, are now being actively investigated.