Investigation of the activity of bronchodilators using a simple but accurate inhalation procedure: forced insufflation.

A simple but accurate inhalation procedure for investigating the activity of antiasthmatic drugs is proposed. The procedure consists of the forced insufflation of the powdered drug, blended with micronised lactose, direct into the tracheobronchial tree. Beta-adrenoceptor agonists (isoproterenol and fenoterol) and antimuscarinics (atropine and ipratropium bromide) were tested using the method of Konzett and Rössler in the guinea-pig; their bronchodilator effects were tested both after forced insufflation and after intravenous administration. The proposed inhalation method supplied close-response curves qualitatively comparable to those obtained by the intravenous route, with the added advantage of more detailed information on the time-course effect. Forced insufflation may be the best procedure for investigating antiasthmatic drugs intended for use as inhalants.