The effect of atropine and albuterol aerosols on the human bronchial response to histamine.

This study was designed to determine whether histamine-induced bronchoconstriction in human asthmatics is mediated by the parasympathetic nervous system and involves cholinergic pathways. Inhalation challenges were performed on 14 adult asthmatic patients using the standardized procedure for inhalation challenge recently recommended by the Asthma and Allergic Disease Centers panel. The effect of pretreatment with either aerosolized atropine sulfate or aerosolized albuterol, a specific beta-2 adrenergic agonist, was studied. The comulative units of histamine required for induction of a positive bronchial response (20% or greater drop in FEV1 from baseline) was used as the basis of comparison of the effects of these drugs. This value was expressed as the PD20-FEV1 to histamine. Analysis of the data showed that aerosolization of sufficient atropie to effect a cholinergic blockade, as shown by inhibition of the bronchial response to inhaled methacholine, only minimally affected the bronchial response to histamine (p less than 0.05). However, the administration of albuterol markedly shifted the response to histamine (p less than 0.005). Although there was a statistically significant change in the mean PD20-FEV1 to histamine following atropine blockade, this effect was small in comparison to that which could be demonstrated with a beta agonist. It would thus appear that the major influence of histamine is not through cholinergic pathways.