Salbutamol is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and chronic obstructive pulmonary disease. Salbutamol is typically used to treat bronchospasm (due to any cause, allergen asthma or exercise-induced), as well as chronic obstructive pulmonary disease. The dose of salbutamol remains controversial. Salbutamol may be quantified in blood or plasma to confirm a diagnosis of poisoning in hospitalized patients or to aid in a forensic investigation. The tertiary butyl group in salbutamol (or albuterol) makes it more selective for β₂-receptors. The drug is sold as a racemic mixture mainly because the (S)-enantiomer blocks metabolism pathways while the (R)-enantiomer shows activity. Salbutamol can be prepared from an acetophenone derivative which is itself derived from salicylic acid.