Albuterol has been used in the acute treatment of
asthma exacerbations for over 25 years. Its cost is low, and delivery can be tailored to allow dose-effect titration. Like other beta-2-adrenergic receptor agonists, it can exist as a racemate of two enantiomers, one active ((R)-
albuterol), and one traditionally considered inert ((S)-
albuterol). Basic investigations in airway cells and models from animals and humans have shown that (R)-
albuterol, in both racemic and single enantiomer formulations, produces changes consistent with both relaxation of airway smooth muscle cells, and the reduction of
inflammation. In contrast, (S)-
albuterol typically has produces effects opposite to those of (R)-
albuterol, i.e., antagonistic to the beneficial desired effects. Coupled with the fact that (S)-
albuterol can persist 12 times longer than (R)-
albuterol within the human circulation, findings suggest that paradoxical effects, sometimes seen with chronic racemic
albuterol use, are due to (S)-
albuterol. A number of clinical studies, to date, have been generally consistent with these findings; however, overwhelming evidence for clinical superiority of the (R)-
albuterol single enantiomer over that within racemic
albuterol remains to be obtained.