Levosalbutamol in the treatment of asthma

With the exception of levosalbutamol, all of the beta2-agonists that are currently in use are racemic mixtures that are composed in equal amounts of (R)- and (S)-enantiomers. Clinical and mechanistic studies have demonstrated that (R)-salbutamol alone provides the beta2-agonist activity that is needed for the relief of bronchoconstriction, as well as the beta2-adrenergically mediated side effects. (S)-Salbutamol, on the other hand, has minimal binding affinity for the beta2-receptor, indicating that its effects are likely to be mediated through another site. Furthermore, there is evidence that (S)-salbutamol opposes the desirable effects of (R)-salbutamol in the racemic mixture and contributes to the development of characteristic features of asthma, such as airway obstruction, bronchial hyperresponsiveness and airway inflammation. Evidence from clinical studies shows delayed recovery from exacerbation of asthma by patients who are exposed to high concentrations of (S)-salbutamol.

Levalbuterol: pharmacologic properties and use in the treatment of pediatric and adult asthma

LEARNING OBJECTIVES

To review the rationale supporting the use of levalbuterol [(R)-albuterol] for the treatment of pediatric and adult asthma.

DATA SOURCES

Peer-reviewed articles, selected abstracts from studies presented at recent professional meetings, and the Xopenex [levalbuterol, (R)-albuterol; Sepracor, Marlborough, MA] Summary Basis of Approval and package insert.

STUDY SELECTION

Institutional review board-approved clinical study protocols.

RESULTS

Levalbuterol is a single isomer beta2-agonist that differs from racemic albuterol by elimination of (S)-albuterol. Levalbuterol is an effective bronchodilator whose primary mechanism of action is unimpeded by (S)-albuterol. Thus, when compared with racemic albuterol, clinically comparable bronchodilation can be achieved with doses that substantially lessen beta-mediated side effects. In chronic or acute treatment of asthma, this favorable therapeutic profile cannot apparently be duplicated by increasing or decreasing the dose of racemic albuterol or by the addition of anticholinergic agents such as ipratropium bromide.

CONCLUSIONS

Levalbuterol seems to provide efficacy and safety advantages in pediatric and adult patients suffering from asthma. Its use may afford a cost benefit as well. More clinical studies are required to extend these observations for use in the treatment of other pulmonary diseases in both adults and children and to determine levalbuterol's impact on long-term therapy of respiratory diseases.