Albuterol has been used for more than 40 years to treat acute asthma exacerbations as a racemic mixture of isomers:
- the active form, (R)-albuterol, or levalbuterol
- (S)-albuterol, classically considered inert
The single-isomer formulation, levalbuterol, has been synthesized (Xopenex) and is used when the racemate is deemed less desirable.
Basic science research indicates that racemic albuterol and levalbuterol can produce effects that favor asthma remediation, including corticosteroid amplification and reduction of inflammatory mediators.
In contrast, (S)-albuterol produces opposite effects. With inhalation of racemic albuterol, circulating (S)-albuterol persists 12 times longer than levalbuterol, suggesting potential for paradoxical effects observed clinically.
However, clinical studies suggest no superiority of levalbuterol over racemic albuterol.
The recent adoption of hydrofluoroalkane MDI formulations has narrowed the cost gap between levalbuterol and racemic albuterol metered-dose inhalers (MDI), but it remains for the nebulized formulations.
Levalbuterol versus albuterol. Ameredes BT, Calhoun WJ. Curr Allergy Asthma Rep. 2009 Sep;9(5):401-9.
Image source: Levosalbutamol (INN) or levalbuterol (USAN), trade name Xopenex, is the R-enantiomer of the short-acting β2-adrenergic receptor agonist albuterol (salbutamol). Wikipedia, public domain.