<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A long-acting beta-2 adrenergic agonist and isomer of formoterol with bronchodilator activity. Arformoterol selectively binds to and activates beta-2 adrenergic receptors in bronchiolar smooth muscle, thereby causing stimulation of adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3',5'-adenosine monophosphate (cAMP). Increased intracellular cAMP levels cause relaxation of bronchial smooth muscle and lead to a reduced release of inflammatory mediators from mast cells. This may eventually lead to an improvement of airway function.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>