The effect of an aerosolized antihistamine, chlorpheniramine maleate, on exercise-induced bronchospasm

We studied the effect on airway function of chlorpheniramine maleate (C), an H₁ antagonist, delivered as an aerosol to 12 asthmatic subjects, 40 minutes before submaximal exercise. The study consisted of three protocol days. A first day established that the asthmatic subjects had exercise-induced bronchospasm (EIB). On the remaining two protocol days, 10 mg of C or a saline placebo (P) were administered by aerosol nebulizer in a double-blind randomized fashion over a 5-minute period. Pulmonary function was measured immediately after the aerosol inhalation as well as 10 and 30 minutes later. A 5-7 minute period of exercise was then performed by each subject on a cycloergometer, and lung function was again measured immediately and 5 minutes after exercise. Thirty minutes after the inhalation of C there was a significant increase in lung function parameters (1.80 ± 0.23 to 2.32 ± 0.34/sec for MEF40%(P); Mean ± 1 SE, P < .05) but not for placebo. MEF40%(P) remained significantly higher on the C day than on the P day following exercise; however, this difference was no greater than the difference seen immediately before exercise. We suggest that C promotes mild bronchodilation of asthmatic airways, and that this effect in EIB may be interpreted as the result of an alteration of baseline airway caliber.