Levosalbutamol (INN) or levalbuterol (USAN) is a short-acting β2-adrenergic receptor agonist used in the treatment of asthma and COPD. It is marketed under the brand name Xopenex, by Sunovion Pharmaceuticals Inc. The drug is the R-enantiomer of its prototype drug salbutamol (INN) or albuterol (USAN). It is available in generic formulations by pharmaceutical companies including Cipla, Teva, and Dey, among others.
There is no reason to use levosalbutamol over salbutamol.
Medical use
Levosalbutamol's bronchodilator properties give it indications in treatment of Asthma and chronic obstructive pulmonary disease (COPD).
Comparison to salbutamol
A 2013 systematic review found no benefit of levosalbutamol compared to salbutamol. There also does not appear to be any difference in safety. It should thus probably not be used in asthma as levalbuterol is much more costly.
Adverse effects
Generally, levosalbutamol is well-tolerated. More common side-effects include a fast heart beat. Less commonly, chest pain/tightness, tremor, dizziness, feeling "faint," a high or low blood pressure, shortness of breath and difficulty breathing may occur.
Rarely occurring but of importance with this drug class are allergic reactions of paradoxical bronchospasm, urticaria, angioedema, hypotension, and collapse.
Pharmacology
Levosalbutamol has similar pharmacokinetic and pharmacodynamic properties to salbutamol.
Mechanism of Action
Activation of beta2-adrenergic receptors on airway smooth muscle leads to the activation of adenylate cyclase and to an increase in the intracellular concentration of cyclic-3', 5' -adenosine monophosphate (cyclic AMP). The increase in cyclic AMP is associated with the activation of protein kinase A, which in turn, inhibits the phosphorylation of myosin 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 beta2-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 beta2-adrenergic receptors. The precise function of these receptors has not been established. However, all beta-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) changes.
Approval
Levalbuterol was originally available only as a solution for nebulizer and eventually become available as a CFC-free metered dose inhaler under the trade name "Xopenex HFA (levalbuterol tartrate) Inhalation Aerosol". The FDA approval date was on March 11, 2005.