Studies in healthy volunteers can demonstrate bronchodilator activity of orally administered drugs.

A panel of healthy volunteers was screened by bronchial histamine provocation. The response used was the flow rate achieved during a partial forced expiratory manoeuvre at a lung volume 30% of the vital capacity above the residual volume. Those subjects who were relatively sensitive to the bronchoconstrictor effects of inhaled histamine took part in a reproducibility study. Those with consistent responses took part in a further study in which the bronchodilator, and bronchoconstriction-protective, effects of orally administered chlorpheniramine, terfenadine and salbutamol were investigated. The technique was able to demonstrate the efficacy of these drugs in non-patient volunteers. Thus it seems to be a suitable method for the early evaluation, in man, of certain drugs with an anti-asthma therapeutic potential. It also provides useful information on the dose and duration of action of compounds prior to the first efficacy trials in patients.