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 in both
dry-powder inhalers (DPIs) and pressurised metered dose inhalers (pMDIs).
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
formoterol decreases the number and severity of asthma attacks. However, 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, and Seretide in the UK).
History and concerns
Salmeterol was developed by the company GlaxoSmithKline in
the 1980s and was released as Serevent in 1990.
In November of 2005, the American FDA released a health
advisory, 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, further
concerns have been raised, by a large metanalysis 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 (eg. as with the combination product
Fluticasone/salmeterol). This seems to occur because although LABAs relieve
asthma symptoms, they also promote bronchial inflammation and sensitivity
without warning
Source: wikipedia GFDL
