The salbutamol molecule in 3-D

The salbutamol molecule - rotatable in 3 dimensions

Salbutamol (ventolin, albuterol) is a bronchodilator agent. It causes relaxation of smooth muscle in the walls of bronchioles, allowing air to flow more easily into the lungs, and as such it is inhaled by asthma sufferers in the event of wheezing attacks.

It is a β-adrenergic agonist - an agent that selectively binds to and activates beta-adrenergic receptors. Its molecular structure closely resembles adrenaline (epinephrine), with a ←hydroxymethyl group instead of a hydroxyl group →, and a ←tertiary butyl group instead of the methyl group→ in adrenaline. It is thought that the tertiary butyl group makes the compound more effective.

The molecule has a chiral centre, and it exists in 2 forms, coded as R and S, or - and +. Salbutamol is normally sold as a racemic mixture, i.e. equal quantities of the 2 forms (enantiomers). Only the (R)-(-)-enantiomer has the pharmacologic activity, and the other (S)-(+)-enantiomer interferes with metabolic pathways which convert and remove both forms of the drug, presumably by blocking enzyme active sites.

Adrenaline (Epinephrine)

Web references

Explainer: Salbutamol, asthma, and what comes next for Froome