They act on the enzyme adenyl cyclase which increases the concentration of cAMP (Cyclic adenosine monophosphate).

[8] The primary noticeable difference of salmeterol from salbutamol, and other short-acting β2 adrenoreceptor agonists (SABAs), is its duration of action.

[2][9] When used regularly every day as prescribed, inhaled salmeterol decreases the number and severity of asthma attacks.

Some animal studies showed developmental malformation when the mother was given several clinical doses orally.

Some of these more serious side effects include Salmeterol has an aryl alkyl group with a chain length of 11 atoms from the amine.

[citation needed] In November 2005, the US Food and Drug Administration (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.

[15] While the use of inhaled LABAs are still recommended in asthma guidelines for the resulting improved symptom control,[16] further concerns have been raised.

[17] This seems to occur because although LABAs relieve asthma symptoms, they also promote bronchial inflammation and sensitivity without warning.