title: Beta2-agonist tolerance and exercise-induced bronchospasm.
abstract: The effect of regular inhaled beta-agonist on the treatment of exercise-induced bronchoconstriction was studied. Eight subjects with exercise-induced bronchoconstriction took 1 week each of salbutamol 200 microg qid or placebo in a random-order, double-blind, crossover study. They then withheld this treatment for 8 hours before performing a dry-air, sub-maximal exercise challenge at a work-rate previously shown to induce a 15% fall in forced expiratory volume in 1 second (FEV1). Five minutes after exercise, they inhaled salbutamol 100, 100, and 200 microg at 5-minute intervals. The mean pre-exercise FEV1 was similar on both study days. However, pretreatment for 1 week with salbutamol led to a significantly greater fall in FEV1 after exercise. The FEV1 remained lower than during the placebo arm despite the administration of salbutamol after exercise. This difference persisted 25 minutes after exercise. It is concluded that regular beta-agonist treatment leads to increased exercise-induced bronchoconstriction and a suboptimal bronchodilator response to beta-agonist. The data suggest that previous regular beta-agonist treatment may lead to a failure to respond to emergency bronchodilator treatment during an acute asthma attack and support current opinion that regular short-acting beta-agonist therapy should not be used to treat asthma.
authors.affiliation: Asthma Research Group, Firestone Institute for Respiratory Health, McMaster University/St Joseph's Hospital, Hamilton, Ontario, Canada.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Hancox
authors.forename: Padmaja
authors.initials: P
authors.lastname: Subbarao
authors.forename: Dennis
authors.initials: D
authors.lastname: Kamada
authors.forename: Richard M
authors.initials: RM
authors.lastname: Watson
authors.forename: Fredrick E
authors.initials: FE
authors.lastname: Hargreave
authors.forename: Mark D
authors.initials: MD
authors.lastname: Inman
mesh_terms: D000293:Adolescent; D000318:Adrenergic beta-Agonists / Q000627:therapeutic use*; D000328:Adult; D000420:Albuterol / Q000627:therapeutic use*; D001250:Asthma, Exercise-Induced / Q000188:drug therapy* / Q000503:physiopathology; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004361:Drug Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D000318:Adrenergic beta-Agonists; D001993:Bronchodilator Agents; D000420:Albuterol