Effects of beta-agonists on breathlessness and exercise tolerance in patients with chronic obstructive pulmonary disease.
In a single-blind placebo-controlled trial in 12 patients with advanced chronic obstructive pulmonary disease (COPD) we compared the effects of nebulized salbutamol (1 mg), clenbuterol (30 micrograms) and placebo (4 ml of normal saline) on spirometric indices (FVC, FEV1), maximal expiratory flows (Vmax50 and Vmax25), the distance walked in 6 min (6MD), assessment of breathlessness by visual analogue scale (VAS), and estimates by the patients of perceived exertion (RPE). Both clenbuterol and salbutamol produced significant increases in FEV1, FVC, Vmax50 and Vmax25. With both drugs, 6MD increased significantly (p less than 0.01) and breathlessness decreased significantly without an appreciable increase in RPE after exercise despite the extra distance covered. The absolute improvements in FEV1 and 6MD after clenbuterol were correlated (r = 0.763, p less than 0.01), but these indices were not correlated after salbutamol (r = 0.121, p greater than 0.1). The lack of correlation between the changes in 6MD and FEV1 after salbutamol might indicate that relief of airways obstruction is not the only explanation for the effects on distance walked, at least with salbutamol.
D000368:Aged; D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D002976:Clenbuterol / Q000494:pharmacology / Q000627:therapeutic use*; D002986:Clinical Trials as Topic; D004417:Dyspnea / Q000188:drug therapy*; D004983:Ethanolamines / Q000627:therapeutic use*; D005541:Forced Expiratory Volume; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000188:drug therapy* / Q000503:physiopathology; D008450:Maximal Midexpiratory Flow Rate; D008875:Middle Aged; D005082:Physical Exertion / Q000187:drug effects*; D010919:Placebos; D014797:Vital Capacity; D014835:Volatilization
D004983:Ethanolamines; D010919:Placebos; D000420:Albuterol; D002976:Clenbuterol