Salmeterol

Salmeterol is a long-acting beta2-adrenergic receptor agonist drug that is currently prescribed for the treatment of asthma and chronic obstructive pulmonary disease COPD. It is currently available as a metered-dose inhaler (MDI) or a proprietary "disk-styled" inhaler that releases a powdered form of the drug.

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Indications

It is a long acting beta-adrenoceptor agonist (LABA), usually only prescribed for severe persistent asthma following previous treatment with a short-acting beta agonist such as salbutamol and is prescribed concurrently with a corticosteroid, such as beclometasone. The primary noticeable difference of salmeterol to salbutamol is that the duration of action lasts approximately 12 hours in comparison with 4–6 hours of salbutamol.

When used regularly every day as prescribed, inhaled salmeterol decreases the number and severity of asthma attacks. However, like all LABA medications, it is not for use for relieving an asthma attack that has already started.

Inhaled salmeterol works like other beta 2-agonists, causing bronchodialation by relaxing the smooth muscle in the airway so as to treat the exacerbation of asthma. The long duration of formoterol action occurs by the formoterol molecules initially diffusing into the plasma membrane of the lung cells, and then slowly being released back outside the cell where they can come into contact with the beta-2 adrenoceptors. Formoterol has been demonstrated to have a faster onset of action than salmeterol as a result of a lower lipophilicity, and has also been demonstrated to be more potent—a 12 µg dose of formoterol has been demonstrated to be equivalent to a 50 µg dose of salmeterol.

Formulations

Currently available long-acting beta₂-adrenoceptor agonists include salmeterol, formoterol, bambuterol, and sustained-release oral albuterol. Combinations of inhaled steroids and long-acting bronchodilators are becoming more widespread; the most common combination currently in use is fluticasone/salmeterol (Advair in the United States, Seretide in the UK).

History and concerns

  Salmeterol, marketed and manufactured by GlaxoSmithKline, in the 1980s and was released as Serevent in 1990. However, the product is under license from Allen & Hanburys.(UK)

In November of 2005, the American FDA released a health advisory[1], alerting the public to findings that show the use of Long-acting β₂-agonists could lead to a worsening of symptoms, and in some cases death.

Whilst the use of inhaled LABAs are still recommended in asthma guidelines for the resulting improved symptom control,^[1] further concerns have been raised, by a large meta-analysis of the pooled results from 19 trials with 33,826 participants, that salmeterol may increase the small risks of asthma deaths and this additional risk is not reduced with the additional use of inhaled steroids (e.g. as with the combination product Fluticasone/salmeterol).^[2] This seems to occur because although LABAs relieve asthma symptoms, they also promote bronchial inflammation and sensitivity without warning.^[3]

See also

• Asthma
• Beta2-adrenergic receptor agonist