There is increasing interest in the use of 'extrafine' aerosols to target the small airways in the management of asthma and COPD.
This study from The Netherlands used previously presented deposition data to assess if submicron (less than 1μm) particles can improve central and deep lung deposition. Prior data had shown that particles in the range 1-3μm are more relevant in this respect.
The following ICS/LABA combination dry powder inhalers were tested in vitro as a function of the pressure drop (2, 4 and 6kPa) across the inhaler: Symbicort Turbuhaler, Seretide Diskus, Rolenium Elpenhaler and Foster (Fostair) NEXThaler.
Obtained fine particle fractions (FPFs) <5μm (as percent of label claim) were divided into subfractions <1, 1-3 and 3-5μm. Differences of up to a factor of 4 were found between the best (Turbuhaler) and worst performing DPI (Elpenhaler), particularly for the FPF in the size range 1-3μm.
The NEXThaler, described as delivering 'extrafine' particles, did not appear to be superior in this size range.
The marked differences in amount and size distribution of the aerosols between the devices in this study likely translates into differences in the total lung dose and drug distribution over the airways.
References: Can 'extrafine' dry powder aerosols improve lung deposition? de Boer AH et al. Eur J Pharm Biopharm. 2015 Jul 26. pii: S0939-6411(15)00316-1. doi: 10.1016/j.ejpb.2015.07.016. [Epub ahead of print]
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