Use of inhaled calcium channel blocking agents in the treatment of asthma.

The inhalation of drugs that are active in the respiratory tract offers the ideal route of administration, since it results in the rapid delivery of appropriate concentrations with a much reduced risk of systemic adverse effects: Problems with regard to poor absorption from the gastrointestinal tract (sodium cromoglycate) or substantial effect on liver metabolism (verapamil) can be avoided. Certain drugs such as antihistamines and ketotifen may be more effective administered by inhalation since high concentrations with reduced unwanted effects can be achieved on the bronchial surface where, in allergic asthma, the critical initial interaction between sensitized mast cells (mucosal?) and allergen with subsequent mediator release occurs. Indeed inhaled verapamil has been shown to be effective in animal models of asthma but not in man. Systemically administered nifedipine gives partial and variable protection against induced asthma in man and its efficacy (with reduced cardiovascular effects) may well be improved by inhalation.