title: Use of exercise challenge to investigate possible tolerance to beta-adrenoceptor stimulation in asthma.
abstract: The effect of prolonged salbutamol administration on beta-adrenoceptor function in asthma has been examined. Six adult patients received salbutamol tablets (16 mg daily) for between 4 and 20 weeks and six adolescents received salbutamol aerosol (800 microgram daily) for 2--5 weeks. Before and after the treatment period the acute bronchodilator response to inhaled salbutamol and the ability of inhaled salbutamol to protect against exercise-induced asthma were examined. Lymphocyte beta-adrenoceptor function was also measured in the patients on tablet therapy. Inhaled salbutamol was less effective in protecting against exercise-induced asthma at the end of the treatment period in the patients who had received tablet therapy, but otherwise there was no significant change in beta-receptor function of either airways or lymphocytes. This apparent loss of efficacy of inhaled salbutamol in the prevention of exercise-induced asthma in some subjects, even when its acute bronchodilator effect is preserved, might reflect differences in the susceptibility of different beta-adrenoceptors to desensitization after prolonged stimulation: its clinical importance remains uncertain.
mesh_terms: D000293:Adolescent; D000328:Adult; D000336:Aerosols; D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D001249:Asthma / Q000188:drug therapy*; D001250:Asthma, Exercise-Induced / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects; D008297:Male; D010366:Peak Expiratory Flow Rate; D011941:Receptors, Adrenergic / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D013607:Tablets; D013618:Tachyphylaxis
chemical_list: D000336:Aerosols; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D013607:Tablets; D000420:Albuterol