Definition and meaning of Levosalbutamol

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Levosalbutamol (INN) or levalbuterol (USAN), trade name Xopenex, is the R-enantiomer of the short-acting β₂-adrenergic receptor agonist albuterol (salbutamol). It is marketed by Cipla as Levolin.

Uses

As a bronchodilator, it is used to treat asthma and COPD. In general, levalbuterol has similar pharmacokinetic and pharmacodynamic properties to albuterol; however, its manufacturer, Sepracor, has implied (although not directly claimed) that the presence of only the R-enantiomer produces fewer side effects.

Physicians sometimes elect to use levalbuterol in patients with a history of supraventricular tachycardia or other arrhythmias because it is thought that levalbuterol may produce less direct effects on β₁-adrenergic receptors in the heart.^{[citation needed]} For similar reasons, some pediatricians also use levalbuterol for patients who experience hyperactivity or jitteriness from racemic albuterol.

Levosalbutamol vs. salbutamol

The use of levosalbutamol (levalbuterol) over the more traditionally used racemic salbutamol (albuterol) is controversial among health care professionals. That using levosalbutamol instead of salbutamol produces less direct effect on β1-adrenergic receptors and/or fewer cardiac side effects has been suggested, but not consistently demonstrated by long term, well-designed clinical trials.

There are differing opinions on whether there is sufficient therapeutic benefit to using levalbuterol that outweighs the 5-10 times higher price tag.^[1][2] In general, it appears that if a clinician and patient feel that a low dose of racemic mixture is causing undesirable side effects, levalbuterol may be a viable alternative.^[3]

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. (See Official FAQ)

Additional studies

In a study of cultured Human Airway Smooth Muscle Cells (HASMC) conducted by Bill T. Ameredes, PhD, and colleagues from the University of Pittsburgh, they concluded that the (S)-isomer found in racemic albuterol had a significant inhibitory effect on the presumed anti-inflammatory effect of dexamethasone, as inferred by increased release of GM-CSF. No P-value however was less than 0.05. The (R)- albuterol isomer was shown to enhance dexamethasone suppression of GM-CSF release. ^[4]

Dr. Ameredes has also proposed that the combination (R)(S)-Albuterol may be problematic. In his Conflict of Interest statement, Dr. Ameredes reports consultancy fees ($8500), advisory fees ($4500) and speaking fees ($7500) from Sepracor, Inc. ^[5]

References