Physical Causes of APSD Changes in Aerosols from OIPs and Their Impact on CI Measurements
The successful implementation of AIM and/or EDA principles to the in vitro assessment of inhalable aerosols emitted from OIPs requires the user of such methods to have a basic understanding of how these particles and/or droplets interact with the human re
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Physical Causes of APSD Changes in Aerosols from OIPs and Their Impact on CI Measurements Helen Strickland, Beth Morgan, and Jolyon P. Mitchell
Abstract The successful implementation of AIM and/or EDA principles to the in vitro assessment of inhalable aerosols emitted from OIPs requires the user of such methods to have a basic understanding of how these particles and/or droplets interact with the human respiratory tract (HRT) upon inhalation. Such processes are inextricably governed by the underlying physical processes associated with these semi-stable systems, and all of the changes influencing particle size affect the entire APSD. This chapter looks at both aspects in some detail, in particular paying attention to how small changes in APSD might be detected by full-resolution CI systems. The information presented herein is a prelude to Chap. 9, in which case studies are presented to demonstrate the sensitivity of EDA metrics to such changes.
3.1 Introduction It is worthwhile briefly reviewing how aerosols are formed in the first place from the different inhaler classes, before exploring the ways in which aerosols emitted by OIPs are currently measured in the laboratory, and later in the book, how the AIM and related EDA concepts may make the process more efficient and effective in the
H. Strickland (*) GlaxoSmithKline, N226, 1011 North Arendell, Zebulon, NC 27597, USA e-mail: [email protected] B. Morgan GlaxoSmithKline, Zebulon Manufacturing and Supply, 1011 N. Arendell Avenue, Zebulon, NC 27597, USA e-mail: [email protected] J.P. Mitchell Trudell Medical International, 725 Third Street, London, ON N5V 5G4, Canada e-mail: [email protected] T.P. Tougas et al. (eds.), Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products, DOI 10.1007/978-1-4614-6296-5_3, © Springer Science+Business Media New York 2013
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quality decision-making process. There are several textbooks available that address the fundamentals of the various aerosol generation processes, and the reader is referred to these for more detailed information [1–5]. Although somewhat older than the other texts, the book edited by Morén et al. is particularly significant because it addresses how inhaler aerosols interact with the respiratory tract in the context of the diagnosis and treatment of lung diseases. The creation of aerosols containing medication for inhalation in general involves one of the following basic processes [6]: (a) Rapid flash evaporation of a metered dose of formulation containing the API(s) in either a high-volatile hydrofluoroalkane (HFA) or an older similarly high- volatile chlorofluorohydrocarbon (CFC) propellant by means of a metered-dose inhaler (MDI). (b) Dispersion of a dry powder containing the API(s); in so-called passive DPIs, dispersion takes place by the energy associated with the vacuum created during inhalation, and in the newer so-called active systems, the energy comes from an external source. (c) Atomization of bulk liquid containing the API(s) by va
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