Airway response to salbutamol: effect of regular salbutamol inhalations in normal, atopic, and asthmatic subjects.

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Abstract
To determine whether resistance to the airway effects of the .beta.-agonist salbutamol would develop in 3 groups of subjects while taking large doses of inhaled salbutamol, 6 normal nonatopic, 6 atopic nonasthmatic and 8 atopic asthmatic subjects were studied by an identical technique. Development of resistance was assessed from salbutamol dose-response studies in which the airway response was measured as specific airway conductance (sGaw). Further evidence was sought in the atopic and asthmatic subjects by measuring the airway response to a standard histamine inhalation challenge and the protective effect of 100 .mu.g salbutamol on this challenge, and by 6-h peak flow recordings. Subjects were assessed before and during 4 wk in which they took inhaled salbutamol regularly in doses increasing to 500 .mu.g qid [4 .times./day] in wk 4. Normal subjects showed a progressive reduction in the bronchodilator (sGaw) response to salbutamol during the 4 wk, indicating the progressive development of resistance. The atopic subjects, both asthmatic and nonasthmatic, showed no reduction in the response to salbutamol during the 4 wk or any change in the response to histamine challenge or in regular peak flow readings. Asthmatic patients do not develop bronchial .beta.-adrenoceptor resistance easily; they and atopic nonasthmatic subjects are apparently less susceptible to its development than normal subjects.