Atropine resistance in asthma: definition and provisional hypothesis

Out of a group of 55 asthmatics, 16 fitted the strict definition of atropine resistance (less than 20% FEV1 response to inhaled anticholinergic drugs, with a 20% or more FEV1 response to subsequent inhalation of beta 2-adrenergic stimulants). 26 were defined as atropine responsive in that they had a 20% or more FEV1 response to anticholinergic drugs. Significantly more atopic than non-atopic asthmatics were in the atropine-resistant group (chi 2 = 6.12; p less than 0.025). Atropine resistance is not related to age. It is probably due to excessive vagal activity resulting from sensitization of vagal irritant receptors by antigen. Atropine resistance appears to be ameliorated by treatment with corticosteroid drugs or disodium cromoglycate. These features suggest a link between allergic and vagal components in asthma.