Tag: SABAs

Why is monotherapy with LABAs contraindicated in asthma?

Why is the chronic use of long-acting beta agonists (LABAs) alone without the concomitant use of an inhaled corticosteroid contraindicated in asthma? What about short-acting beta agonists (SABAs), can they be used without taking an inhaled corticosteroid at the same time?

Activation of β2-adrenoceptor promotes bronchodilation. β2-adrenoceptor agonists are the most potent bronchodilators in current clinical use. Inhaled short-acting beta agonists (SABAs), for example salbutamol (known as albuterol in the USA) have a bronchodilator effect that lasts for 4 to 6 hours, while long-acting beta agonists (LABAs), for example salmeterol, have a  bronchodilator effect that lasts for 12 to 24 hours (depending upon the drug). SABAs are used to relieve acute bronchoconstriction. Use of a SABA can be a life-saving intervention during an asthma attack. In contrast, LABAs are used chronically to mainain bronchodilation improving airway function and controlling occurance of symptoms.

Chronic use of LABAs causes tolerance due to downregulation of β2-adrenoceptors. This is associated with an increased risk of mortality in patients with asthma. Therefore the use of LABAs alone is contraindicated. The downregulation of β2-adrenoceptors by chronic use of LABAs can impair the response to SABAs when they are need for acutre relief of symptoms during an asthma attack.

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Controllers versus preventers for asthma

Sometimes there is confusion over the usage of the term “controllers” in the treatment of asthma.

The term “controllers” can refer to the long-acting beta agonists (LABAs). But sometimes it is used to refer to both the LABAs and the anti-inflammatory drugs such as corticosteroids. As the LABAs and anti-inflammatory drug have different roles in asthma treatment, the term “preventers” can be used to refer specifically to the anti-inflammatory drugs.

The situation can be further confused by the fact that LABAs are no longer used alone as controllers. They are now always prescribed together with corticosteroids, often in combination inhalers.  This is because the use of beta-2 agonists alone leads to beta-2 adrenoceptor tolerance and increased risk of asthma-related death. Concomitant use of a corticosteroid helps to reduce beta-2 adrenoceptor tolerance and treats the underlying inflammatory disease.

In our lectures, we will use the terminology as follows:

Preventers reduce swelling and inflammation in the airways, stopping them from being so sensitive and reducing the risk of severe attacks. Thus they prevent the risk of recurrent attacks.

Controllers are long-acting beta-adrenoceptor agonists (LABAs) taken regularly at the same time daily to provide long-acting bronchodilation.

Relievers are short-acting beta-2 adrenoceptor agonists (SABAs) used “as needed” to relieve asthma attacks.

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