Evidence based review on levosalbutamol

Salbutamol, the most commonly used bronchodilator, is a chiral drug with R (levosalbutamol) and S-isomers (also known as enantiomer). The commonly used formulation is a racemic mixture that contains equal amounts of both R and S isomers. Levosalbutamol is the therapeutically active isomer and has all the beta 2 agonist activity. Until recently S-salbutamol was considered inert filler in the racemic mixture but animal as well as human studies have shown that S-salbutamol is not inert rather it may have some deleterious effects. Enantioselective metabolism of salbutamol leads to higher and sustained plasma levels of S-salbutamol with repeated dosing. There has been concern that chronic use of racemic salbutamol may lead to loss of effectiveness and clinical deterioration. Formulation of salbutamol containing only R- isomer (levosalbutamol) has been available in international market since last few years. Clinical trials in acute as well as chronic asthma in adults as well as children have shown that it has therapeutic advantage over racemic salbutamol and also is more cost effective. But, large multicenter trials are needed to prove its therapeutic superiority and cost-effectiveness in long term.