[Pharmacological properties of salmeterol]

Salmeterol is an original molecule characterized by its long duration of action (greater than 12 hrs in humans). Salmeterol is a highly selective beta-2 agonist that is from 2 to 15 times more potent than salbutamol on beta-2 receptors of bronchial smooth muscle and 10,000 times more potent than isoprenaline on beta-1 receptors. The duration of action of salmeterol on bronchial smooth muscle has been shown to be much superior than all other beta-2 sympathomimetics that have been studied, including formoterol. Salmeterol has two side chains that are linked by a long hydroxycarbon chain. Its long duration of action could be explained by the link to the cell membrane through an exo-site which is distinct from the beta-2 receptor. In vitro and in the animal model, salmeterol has a triple effect: inhibition of the liberation of inflammatory mediators (histamine, prostaglandins, leukotrienes), inhibition of cell influx and of protein extravasation. The relevance of this effect remains to be establish in humans.