Abstract
Recently, statistical techniques such as design of experiments are being applied for efficient optimization of oral formulations. To use these statistical techniques for inhalation formulations, efficient methods for rapid determination of the aerodynamic particle size distribution of many samples are needed. Therefore, we aimed to develop a simple method to measure aerodynamic particle size distribution that closely agrees with the results of inhalation characteristic tests. We added attachments for dispersion to the aerodynamic particle sizer (APS) so that formulations could be dispersed under the same condition as for multi-stage liquid impinger (MSLI) measurement. Then, we examined the correlation between MSLI and APS using lyophilizate for dry powder inhalation formulations that generate porous particles just on inhalation. It is difficult to obtain the accurate aerodynamic particle size distribution of porous particles by APS because the particle density is difficult to estimate accurately. However, there was a significant correlation between MSLI and APS when the particle density settings for APS measurement was calculated by a conversion factor based on the result of MSLI. The APS with dispersion attachments and this conversion factor can measure a number of samples in a short time, thereby enabling more efficient optimization of dry powder inhalers.
Highlights
Available inhaled drug delivery systems for topical administration to the lung can be divided into three principal categories: nebulizers, pressurized metered-dose inhalers, and dry powder inhalers (DPIs)
The main features of the aerodynamic particle sizer (APS) with dispersion attachments are that formulations are aerosolized under the same condition as for multi-stage liquid impinger (MSLI) measurement, which reflects human inhalation, and that the size distribution of the generated particles can be measured quickly by APS (Figure S1)
There was a significant correlation between results of MSLI and that of the APS with dispersion attachments and the conversion factor
Summary
Available inhaled drug delivery systems for topical administration to the lung can be divided into three principal categories: nebulizers, pressurized metered-dose inhalers, and dry powder inhalers (DPIs). In the DPI formulations, aerosols need to have aerodynamic diameters between 0.5 and 5 μm to deliver the drug to the lungs [3,4]. The aerodynamic diameter is defined by Equation (1) [5]. Either particles are made with standard density with geometric diameters between 0.5 and 5 μm, or they are created with a non-standard density with aerodynamic diameters between 0.5 and 5 μm in contrast to geometric diameters outside the standard range. Conventional DPIs use the first strategy, whereas large porous particles provide an example of the second strategy [6,7]. Large porous particles are recently becoming popuPlhaarrmaasceutthices 2t0e20c,h1n2,ixqFuOeR fPoEErRbRoEtVhIElWocal and systemic applications by the pulmonary ro2uotfe1t4o the lungspa[8rt–ic1l2e]s. T[i2m1,e2-o3f]-.fliTgOhtF(TmOFe)asmueraesmureenmteinst eisaosnyetmo eptheordfotrhmat,cbanutmtehaesusreettthinegs of particaleeroddeynnsaimtyicgpraerattilcyleasffizeecdt itshtreibruetsiounltsofomf amneyassaumrpelmeseinnta[2sh4o–r2t6t]i.mTeo[2o1b,2t3a]i.nTOacFcmureaatseuraeemroedntyinsamic particelaesysitzoepdeirsftorrimbu, btiuotnthbeyseTtOtinFgms oefapsaurrteicmleednetn, stihtye gpraerattilcyleafdfeecnt sthiteyrneseueldtssotfombeeascuarlceumleantet d[24a–c2c6u]r. ately
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