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, and (S)-
albuterol, classically considered inert. The single-isomer formulation,
levalbuterol, has been synthesized recently and used therapeutically when the racemate is deemed less desirable. Basic investigations indicate 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. Although mainly consistent with basic findings, clinical studies suggest no overwhelming superiority of
levalbuterol over racemic
albuterol; however,
levalbuterol's effects may be greatest in moderate to severe
asthma patients, especially with racemic
albuterol overuse. Recent adoption of the
hydrofluoroalkane formulation has narrowed the cost gap between
levalbuterol and racemic
albuterol metered-dose inhalers, but it remains for the nebulized formulations. Thus, physician selection of these drugs has remained dependent on experience,
pharmaceutical knowledge, and established prescribing habits combined with cost factors, formulary structures, and availability, such that racemic
albuterol is still used significantly compared with
levalbuterol to treat acute
asthma exacerbations.