title: Asthma pathophysiology and evidence-based treatment of severe exacerbations.
abstract: OBJECTIVE
  The pathogenesis of asthma and the treatment approach for acute exacerbations are described. The pharmacology, efficacy, safety, and cost of the beta2 agonist, albuterol, a racemic mixture of equal amounts of R- and S-enantiomers, and levalbuterol, the R-enantiomer, are compared.
  
  
  CONCLUSIONS
  Asthma symptoms are the result of bronchial hyperresponsiveness, bronchospasm, and chronic airway inflammation. Short-acting, inhaled beta2 agonists; oxygen; intravenous fluids; and corticosteroids are the mainstays of treatment for acute exacerbations. The R-enantiomer of albuterol is responsible for bronchodilation. The S-enantiomer exhibits broncho-constricting activity in vitro, which may be mediated by muscarinic receptors and may be opposed by adding the anticholinergic agent ipratropium bromide. Levalbuterol improves pulmonary function to a greater extent than racemic albuterol and reduces the need for costly hospitalizations in patients with acute asthma exacerbations.
  
  
  CONCLUSIONS
  Levalbuterol is an alternative to racemic albuterol with the potential to improve patient outcomes and reduce costs in the treatment of acute asthma exacerbations.
authors: Department of Emergency and Hospital Medicine, Summit Medical Group, 80 Division Avenue, Summit, NJ 27599-0001, USA. dschreck@comcast.net
authors: David M
authors: DM
authors: Schreck