Long-acting β adrenoceptor agonists are usually prescribed for moderate-to-severe persistent asthma patients or patients with chronic obstructive pulmonary disease. They are designed to reduce the need for shorter-acting β2 agonists such as salbutamol, as they have a duration of action of approximately 12 hours in comparison with the 4-to-6-hour duration of salbutamol, making them candidates for sparing high doses of corticosteroids or treating nocturnal asthma and providing symptomatic improvement in patients with COPD. With the exception of formoterol, long-acting β2 agonists are not recommended for the treatment of acute asthma exacerbations because of their slower onset of action compared to salbutamol. Their long duration of action is due to the addition of a long, lipophilic side-chain that binds to an exosite on adrenergic receptors. This allows the active portion of the molecule to continuously bind and unbind at β2 receptors in the smooth muscle in the lungs.
Medical uses
When combined with inhaled steroids, β adrenoceptor agonists can improve symptoms. In children this benefit is uncertain and they may be potentially harmful. They should not be used without an accompanying steroid due to an increased risk of severe symptoms, including exacerbation in both children and adults. A 2018 meta-analysis was unable to determine whether an increase serious adverse events reported in the previous meta-analysis on regular salmeterol alone is abolished by the additional use of regular inhaled corticosteroid. Large surveillance studies are ongoing to provide more information. There were no asthma-related deaths and few asthma-related serious adverse events when salmeterol is used with an inhaled steroid. At least with formoterol, an increased risk appears to be present even when steroids are used and this risk has not been ruled out for salmeterol.
Agents
Some of the currently available long-acting β2 adrenoceptor agonists include:
Several long-acting β adrenoreceptor agonists have a duration of action of 24 hours, allowing for once-daily dosing. They are considered to be ultra-long-acting β adrenoreceptor agonists and are now approved.
vilanterol is the ultra-LABA not available by itself but only as a component of combination drugs:
* with fluticasone furoate: Breo Ellipta, Relvar Ellipta. This second medication in this combination is the synthetic inhaled corticosteroid fluticasone furoate. This product was approved by the FDA on May 2013 as once-daily inhaled therapy for the treatment of chronic obstructive pulmonary disease
* with umeclidinium bromide: Anoro Ellipta. Umeclidinium bromide is a long-acting. This combination was approved by the FDA on December 18, 2013 for the long-term maintenance treatment of COPD. On March 28, 2014, it was approved in European countries and in Russia under the same trade name
While 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 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. This seems to occur because although LABAs relieve asthma symptoms, they also promote bronchial inflammation and sensitivity without warning. On February 18, 2011, the FDA issued a safety alert for long-acting β agonists.
