Comparison of bronchodilator responses of levosalbutamol and salbutamol given via a pressurized metered dose inhaler: a randomized, double blind, single-dose, crossover study.

Background: Salbutamol, the most widely used short-acting beta(2)-agonist, consists of a racemic mixture of equal amounts of two enantiomers, (R)-salbutamol and (S)-salbutamol. The bronchodilator effects of salbutamol are attributed entirely to (R)-salbutamol (levosalbutamol), while (S)-salbutamol has been shown to possess bronchospastic and pro-inflammatory effects both in vitro and in vivo studies. Levosalbutamol, the (R)-enantiomer of salbutamol is currently available only in a liquid formulation for use via a nebulizer. Recently, levosalbutamol to be administered via a pressurized metered dose inhaler (pMDI) has been developed.

Aims: To compare the time-dependent bronchodilator responses of single doses of 100mcg levosalbutamol and 200 mcg racemic salbutamol administered via a pMDI in subjects with stable mild-to-moderate bronchial asthma over a period of 6h.

Methods: Single doses of 100 mcg levosalbutamol, 200 mcg salbutamol and placebo were administered with a pMDI in 30 stable asthmatic subjects in a randomized, double-blind, placebo-controlled, three-way cross over study. Forced expiratory volume in 1s (FEV(1)) and forced vital capacity (FVC) were measured at baseline, and over 6h post-study drug administration.

Results: Levosalbutamol and salbutamol produced significantly better bronchodilator responses than placebo. Both the drugs showed equivalent time-dependent bronchodilator responses as measured by area under curve for percent change in FEV(1) and FVC over 6h. The time to onset of action, mean maximum bronchodilator response and duration of bronchodilator response were similar between levosalbutamol and salbutamol.

Conclusion: A single dose of 100 mcg levosalbutamol administered by a pMDI produced a similar bronchodilator response as salbutamol when measured over 6h in subjects with stable, mild-to-moderate bronchial asthma.