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Drug Delivery
Published in John G Webster, Minimally Invasive Medical Technology, 2016
The common technologies for inhaled delivery of medicine are metered dose inhalers, dry powder inhalers and nebulizers. Metered dose inhalers are pressurized containers of medicine, which deliver an aerosol containing the medicine for delivery. They are very common, due to their convenience of use, low cost and portability. The problems with metered dose inhalers are outlined above. Dry powder inhalers are breathing-activated inhalers that deliver micronized powders of medicine. These overcome the problems associated with the sudden burst delivered by metered dose inhalers, but tend to provide a less effective dose of medicine due to clumping of the particles. Nebulizers provide a constant atomized mist of medicine. A gentle steam is provided, which is inhaled through normal breathing. Nebulizers solve the major problems of inhaled delivery as far as effectiveness, however they tend to be bulky, expensive and require an electric outlet for continued operation. Significant efforts have been and are being made to overcome the problems with each of these delivery systems.
Unlocking further understanding of the atomization mechanism of a pressurized metered dose inhaler
Published in Aerosol Science and Technology, 2022
B. J. Myatt, H. K. Versteeg, G. K. Hargrave, E. J. Long, B. Gavtash, D. A. Lewis, T. Church, G. Brambilla
Pressurized metered dose inhalers (pMDIs) are self-contained drug delivery devices for controlling symptoms of asthma and COPD (Stein and Thiel 2017). In Europe, 48% of inhaled medications sold between 2002 and 2008 were pMDIs (Myrdal, Sheth, and Stein 2014) and a recent estimation suggests that 262 million people suffer from asthma worldwide (World Health Organisation 2021). Drug particles with mass median aerodynamic diameter in the range of 0.5 to 5 µm are required for lung deposition (Stahlhofen, Rudolf, and James 1989) and effective bronchodilator treatment (Shekunov et al. 2007; Ivey, Vehring, and Finlay 2015). These are produced in large quantities by pMDIs, but a substantial proportion of the drug dose is known to deposit in the oral cavity. This reduces drug delivery efficiency and therapeutic effectiveness (Everard 2000; Newman 2005) and can result in side effects, such as oral candidiasis, dysphonia, bronchospasm, and systemic exposure (Yarbrough, Mansfield, and Ting 1985). Poor patient coordination with the pMDI device is partly responsible for oropharyngeal drug deposition, but other leading causes are the presence of very large non-respirable droplets in pMDI aerosols, as well as high spray plume velocities leading to inertial impaction and turbulent diffusion (Stein and Gabrio 2000; Lewis 2007). Little is known about the factors that are responsible for these aerosol characteristics.