The Clinical Difference Between Salmeterol and Formoterol
Both salmeterol and formoterol are considered long-acting beta-agonists. These agents have been commonly used in the setting of asthma and COPD. Each of these agents is most commonly combined with an inhaled corticosteroid. Budesonide is coupled with formoterol in the brand name product Symbicort. Salmeterol is most commonly coupled with fluticasone in the brand name product Advair. Is there a clinical difference between salmeterol and formoterol? A few years ago, I probably would have said I didn’t know. This has now changed with the new GINA initiative.
The Global Initiative for Asthma (referred to as GINA) was released in 2019 and tells us that there is absolutely a difference between these two long-acting beta-agonists. GINA allows for the use of Symbicort in a patient with an acute asthma exacerbation.
From the GINA guidelines, here’s the recommended dosing for this indication. Budesonide 80 mcg/formoterol 4.5 mcg or budesonide 160 mcg/formoterol 4.5 mcg: 1 inhalation as needed; may repeat if no relief. Maximum: Up to 12 inhalations/day.
Can we use salmeterol/fluticasone for the same indication of acute asthma exacerbation? Absolutely not! If you ever see an order for PRN Advair, you should question it with boldness. The reason this is true lies in the pharmacokinetics.
The primary clinical difference between salmeterol and formoterol lies in the pharmacokinetics of the drugs. Salmeterol’s onset of action is around 30 minutes. As you could imagine, in an emergency situation of respiratory distress, 30 minutes is an unacceptable time period to wait for relief. Formoterol, on the other hand, has an onset of action of 3 minutes or so. This is much more conducive to relieving an acute asthma exacerbation. This pharmacokinetic difference between these two agents explains why the GINA guidelines do not recommend Advair for the use of an acute asthma exacerbation. If you’d like to learn more specifically about budesonide/formoterol, you can listen to one of my recent podcast episodes. You can also check out this case for more asthma-related pearls.
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