and lowers intracellular ionic calcium concentrations, resulting in muscle relaxation. Levosalbutamol relaxes the smooth muscles of all airways, from the trachea to the terminal bronchioles. Increased cyclic AMP concentrations are also associated with the inhibition of the release of mediators from mast cells in the airways. Levosalbutamol acts as a functional agonist that relaxes the airway irrespective of the spasmogen involved, thereby protecting against all bronchoconstrictor challenges. While it is recognized that β2 adrenergic receptors are the predominant receptors on bronchial smooth muscle, data indicate that there are beta receptors in the human heart, 10–50% of which are β2 adrenergic receptors. The precise function of these receptors has not been established. However, all β adrenergic agonist drugs can produce a significant cardiovascular effect in some patients, as measured by pulse rate, blood pressure, and restlessness symptoms, and/or electrocardiographic (ECG). Approval and names Levosalbutamol is the INN while levalbuterol is the USAN. Levalbuterol was approved in the United States as a solution to be used with a nebulizer device in March 1999 and in March 2015 became available in a formulation with a metered-dose inhaler under the trade name Xopenex HFA (levalbuterol tartrate inhalation aerosol). See also Salbutamol — the racemic mixture containing both (R)-(−)- and (S)-(+)-enantiomers References External links Beta2-adrenergic agonists Chemical substances for emergency medicine Enantiopure drugs Phenylethanolamines Phenols