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Particle size determination of metered dose inhalers with inertial separation methods: Apparatus A and B (BP), Four Stage Impinger and Andersen Mark II Cascade Impactor

1995; Elsevier BV; Volume: 116; Issue: 1 Linguagem: Inglês

10.1016/0378-5173(94)00263-5

1873-3476

Peter Holzner, Bernd W. Müller,

Inhalation and Respiratory Drug Delivery

The particle size of pharmaceutical aerosols is the main factor governing their deposition in the human respiratory tract. Of the many methods that are available for particle size analysis of aerosols, inertial methods have been found to give the most representative results, as compared to in vivo conditions. Two devices working on this principle have been included in the British Pharmacopoeia, Apparatus A and Apparatus B. One of their disadvantages is, however, that they only divide the aerosol particles into two fractions and do not yield a particle size distribution. Therefore, a third device, the Multistage Cascade Impactor no. 1, has additionally been taken up in the USP. Apart from Apparatus A and B, two devices that comply with this USP monograph were used in this study. The first was a self-made Four Stage Impinger, the second device being the Andersen Mark II Cascade Impactor with eight stages and a preseparator. The aim of this study was to compare the results of particle size analysis of different test aerosol formulations in metered dose inhalers with these four devices. In the first part of the study, one formulation was analyzed with all four methods. There was excellent agreement between Apparatus A and the Four Stage Impinger on the one hand and between Apparatus B and the Andersen Impactor on the other. In the second part of the study, Apparatus A and the Four Stage Impinger were compared in greater detail by sizing five more aerosol formulations. There was again excellent agreement in the fine particle fractions as determined with the two methods. By comparing the fraction of particles below 2.8βm additionally, the Four Stage Impinger allowed better distinction between the aerosol formulations than Apparatus A. All in all, each of the four devices turned out to be useful for determining the particle size of an aerosol. Considering the analytical effort necessary and the amount of data generated with each of the devices, the Four Stage Impinger appeared to be the most effective.