Formoterol

Formoterol is a relatively selective long-acting agonist of beta2-adrenergic receptors, although it does carry some degree of activity at beta1 and beta3 receptors. Beta2 receptors are found predominantly in bronchial smooth muscle (with a relatively minor amount found in cardiac tissue) whereas beta1 receptors are the predominant adrenergic receptors found in the heart - for this reason, selectivity for beta2 receptors is desirable in the treatment of pulmonary diseases such as COPD and asthma. Formoterol has demonstrated an approximately 200-fold greater activity at beta2 receptors over beta1 receptors.

On a molecular level, activation of beta receptors by agonists like formoterol stimulates intracellular adenylyl cyclase, an enzyme responsible for the conversion of ATP to cyclic AMP (cAMP). The increased levels of cAMP in bronchial smooth muscle tissue result in relaxation of these muscles and subsequent dilation of the airways, as well as inhibition of the release of hypersensitivity mediators (e.g. histamine, leukotrienes) from culprit cells, especially mast cells.