Study of a new oral beta-adrenergic drug,clenbuterol, in patients with chronic bronchitis

Summary In a double-blind, placebo-controlled, incomplete cross-over study the bronchodilator, cardiovascular, respiratory and metabolic effects of 3 different oral doses of clenbuterol were studied in 12 patients suffering from partly reversible airways obstruction due to chronic bronchitis. The ventilatory response to oral clenbuterol or placebo was assessed by measurement of specific airway resistance (sRaw) to detect changes in central airways, and of flow at 85% of vital capacity (_{85% VC}) to detect change in peripheral airways. Clenbuterol 20, 30 and 40 µg produced a significant decrease in sRaw between 15 and 480 min after administration. Its effect on the large airways was not related to the dose. Clenbuterol 30 and 40 µg caused a significant increase in_{85% VC} between 60 and 480 min after administration. After 20 µg a significant improvement in_{85% VC} was found between 120 and 240 min. The over-all effect of 30 µg on the small airways was significantly more pronounced than that of 20 µg and was more sustained than that of 40 µg 120 min after administration. No significant changes in heart rate, ECG or blood pressure were noted. Decreases in PaO₂ and O₂-saturation after clenbuterol were not related to dose. Slight falls in PaO₂ and O₂-saturation were also observed after placebo. These observations are briefly discussed. There was negligible lipid mobilization after either the placebo or bronchodilator. A slight but insignificant rise in blood glucose was observed after both 30 and 40 µg of clenbuterol.