Small particle formoterol may achieve better deposition in small airways compared with large particle salmeterol

This small study from the UK used impulse oscillometry (IOS) to compare single and repeated dosing effects of small- and large-particle long-acting beta-agonists.

16 patients (mean age 43 years) received either 12 mcg of small-particle hydrofluoroalkane 134a-formoterol solution or 50 mcg of large-particle salmeterol dry powder twice daily plus inhaled corticosteroid for 1 to 2 weeks with a 1- to 2-week washout period in between. Measurements were made over 60 minutes after the first and last doses.

At baseline, FEV1 was 80%; FEF25-75, 48%; total airway resistance at 5 Hz, 177%; peripheral airway resistance as the difference between 5 and 20 Hz, 0.18 kPa·L-1·s.

After the first dose, there were greater improvements with formoterol versus salmeterol in all IOS outcomes and FEF25-75, but not FEV1, at 5 minutes (these were not sustained over 60 minutes). After the last dose, all IOS outcomes, but not FEV1 or FEF25-75, were better with formoterol over the entire 60 minutes.

Improvements in IOS outcomes but not spirometry results occurred after chronic dosing with formoterol compared with salmeterol. This might reflect better deposition to the entire lung, including the small airways.


Effects of formoterol or salmeterol on impulse oscillometry in patients with persistent asthma. Manoharan A. et al. J Allergy Clin Immunol. 2015 Jul 25. pii: S0091-6749(15)00861-1. doi: 10.1016/j.jaci.2015.06.012. [Epub ahead of print]
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As some of you know, I have been the Editor of the World Allergy Organization (WAO) Small Airways Working Group "What's New?" monthly summary since 2011. The summary features the top 3 asthma/small airways articles each month. The article above is part of the project. The archive is here:

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