Dose response relationship of clenbuterol (NAB 365) as a solution for inhalation

The dose-response relationship of the new bronchodilator Clenbuterol (NAB 365, Boehringer Ingelheim) was tested in 12 patients with chronic obstructive lung disease. Clenbuterol is a beta-2-sympathicomimetic, from a series of substituted phenylethanolamines, and it is characterised by good absorption and prolonged action after systemic administration. The action of four different doses of Clenbuterol inhalation solution (6, 12, 24 and 48 µg corresponding to 2, 4, 8 and 16 drops of a 0.006% solution) was assessed after a single inhalation on 4 successive days. The parameters monitored were bronchial resistance and FEV1. The effect of all four doses was the same, both in respect of improvement in FEV1 and of decrease in bronchial resistance. The increase in expiratory volume and the decrease in bronchial resistance lasted for 6 h. The results show that for inhalation therapy Clenbuterol is a potent, selective bronchodilator, which is largely free of sideeffects. It has still to be determined whether a maximal effect could be achieved with a lower dose 6 µg.