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

Summary Background Salbutamol, the most widely used short-acting β2 -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 100 mcg levosalbutamol and 200 mcg racemic salbutamol administered via a pMDI in subjects with stable mild-to-moderate bronchial asthma over a period of 6 h. 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 1 s (FEV1 ) and forced vital capacity (FVC) were measured at baseline, and over 6 h 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 FEV1 and FVC over 6 h. 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 6 h in subjects with stable, mild-tomoderate bronchial asthma.