Effects of topical betaxolol, timolol, and placebo on pulmonary function in asthmatic bronchitis

To evaluate the effects of two beta-adrenergic blocking agents on cardiopulmonary function, we investigated two topical ophthalmologic preparations, betaxolol 1% and timolol 0.5%, in nine patients (eight men and one woman, ranging in age from 25 to 69 years) with reactive airway disease. The randomized, double-masked, crossover study used placebo eyedrops as the control, and each drug was tested on separate days. Spirometric measurements, respiratory rate, pulse rate, and blood pressure were observed at frequent intervals for four hours after the test solutions were instilled. At the end of the test, an inhaled beta-adrenergic stimulant (isoproterenol) was administered, and the measurements were repeated. Timolol produced a significant decrease in airflow, measured by forced expiratory volume in one second (FEV₁) and the ratio of FEV₁ to vital capacity at each observation time beyond 15 minutes. Betaxolol and placebo eyedrops produced no significant change from control values. These results suggested that timolol can adversely affect patients with reactive airway disease. Betaxolol eye-drops, conversely, caused no decrease in airflow in the same patients with proven airway disease.