Clinical experience with levalbuterol

Although racemic albuterol is an effective bronchodilator, regular use has been associated with some loss of bronchodilator potency, decreased protect ion against bronchoprovocation, increased sensitivity to allergen challenge , and increased sensitivity to some bronchoconstrictor stimuli. In experime ntal animals racemic albuterol has produced bronchial hyperresponsiveness, which could also be induced by administration of (S)-albuterol, These findi ngs suggest that the pure or homochiral formulation of (R)-albuterol (leval buterol) might be more effective as a bronchodilator than the racemic form. Single doses of levalbuterol provided more prolonged protection against me thacholine challenge than the racemate, whereas (S)-albuterol significantly increased sensitivity to methacholine, In a l-week study in adults, equiva lent amounts of pure levalbuterol provided greater bronchodilation than did similar amounts of levalbuterol given as racemic mixtures. Furthermore, af ter 4 weeks, the baseline morning FEV1 was lower in those receiving the rac emate than in those receiving placebo or levalbuterol. In a single-dose stu dy in children, the same conclusion regarding greater bronchodilation with pure levalbuterol compared with the same amount of levalbuterol in a racemi c mixture was confirmed. These studies appear to confirm the greater effica cy of pure levalbuterol over a similar amount in a racemic mixture. This im plies a deleterious effect of (S)-albuterol on both the acute bronchodilato r response and baseline airway caliber, the exact mechanism of which will r equire further investigation.