Site of beta-adrenergic receptors in the respiratory tract: use of fenoterol administered by two methods.

We have compared the short-term effects of buccal ad ministration of a solution containing 500,,n of fenotcrol and of aerosol administration of 200,,g and 400/xg of fenoterol from a metered-dose inhaler with administra tion of a placebo in ten asthmatic subjects. The study was performed in double-blind fashion, with randomized administration of drugs or placebo, to determine if the systemic absorption of /3;>-adrenergicagonists from the buccal mucosa affected airways or if there were buccal /?i:-adrenergic receptors mediating the responses of the airways. The bronchodilatation after each treatment, assessed by the mean area (±SE) under the curve of the forced expiratory volume in one second, was as follows: placebo, 0.34 ± 0.30 L/hr; buccal administration of 500/xg of fenoterol, 0.64 ±0.20 L/hr (P > 0.05); in halation of 200,,g of fenoterol, 2.05 + 0.36 L/hr (P < 0.01); and inhalation of 400Fg of fenoterol, 2.25 ±0.48 L/hr (P < 0.01). We conclude that inhalation of 200/in of fenoterol is as effective as inhalation of 400,,g to moderate obstruction of the airways and that for the usual doses of fenoterol given by metered-dose inhaler, it is only the aerosol actually delivered to the airways that determines the bronchodilator effect. This indicates that systemic absorption of metered doses of fenoterol does not cause significant bronchodilatation and that there are no /J-adrenergic receptors in the buccal mucosa mediating responses of the airways.