Validating AIM-Based Instrumentation and Associated Measurement Techniques - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 339

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8
6
4
2
0
-2
-4
-6
-8
-10

DPI1 DPI2 DPI3 pMDI Mean

all inhalers

Inhaler type

Fig. 10.67 Differences in FPM between the full NGI and the filter method for the inhaler types
used in the study reported by Svensson and Berg; error bars are 95% confidence intervals ( From
[ 59 ]— courtesy of M. Svensson )

DPI-1 compared to the other inhaler types, and they provided the following rationale
from their findings:

1. The nozzle-filter methodology is a less mature methodology in their laboratory,
whereas the outlet “O”-cup has been established and used in development stud-
ies for several years.
2. DPI-1 as a device and the three formulations used in this device were both con-
cepts in early development phase at the time when the work was undertaken, so
the dosing properties may be more variable than the other inhalers that are prod-
ucts that are in late stage development.

Importantly, they did not observe that any particular stage was better (or worse)
suited to be used in these filter methodologies (see marker shape in Fig. 10.66 ) and
that no outliers were obtained in the data set.
Svensson and Berg went on to calculate the mean differences (presented in per-
centage terms of the found mass in the NGI test) between the NGI and the filter
methods for each of the inhaler types (Fig. 10.67 ). Both negative and positive differ-
ences were observed, ranging from +5% to −2.5%. DPI-3 displayed significant dif-
ference between NGI and filter method, but when all 91 mean values were regarded
as one data set, the difference became minimal (around 1%) and importantly, no
significant difference was obtained between the two methods (standard NGI versus
Filter concepts).
From a practical perspective, Svensson and Berg made the judgment that the
nozzle-filter-abbreviated approach is about two times faster than the external
filter method [ 59 ]. Moreover, since the external filter method, in its current
design, includes a disposable plastic fixture, the nozzle filter is preferable from