Aerosols including metered-dose inhalers and dry powder inhalers have the ability to deliver drugs to the lungs, enabling these devices to be significant in medicine and pharmaceuticals. A critical component within these aerosols includes the particle size distribution and shape. The significance of particle size analysis within aerosols will be explored further in this article for the application of inhalers.
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Aerosols consist of solid or liquid particles that can be suspended in a gas called a propellent; pharmaceutical aerosols comprise fine particles of a drug that is contained under tight pressure within a container. These particles are then released as a spray when applied by a patient by pushing a button.
Pharmaceutical aerosols can be inhaled via the mouth and can be delivered into the respiratory tract for the treatment of various disorders including associated lung diseases. These aerosols can be stored within two types of inhalers, such as metered-dose inhalers (MDIs) as well as dry powder inhalers (DPIs).
Metered-dose inhalers can be used for providing patients with a particular dose of various drugs and can be used to relax the muscles of the airway as well as aid with reducing inflammation. DPIs can be used as alternatives for conventionally used aerosol-based inhalers and can produce a powder that carries a dose of treatment to the lungs in powder form.
These treatments can be used for the treatment of lung diseases that are associated with airflow obstruction resulting in difficulty breathing, as well as other disorders such as asthma and respiratory infections.
The particles within an aerosol require characterization in order to develop pharmaceutical formulations of the drug treatment. The biodistribution and absorption of the drug can determine the efficacy of the treatment, which signifies the importance of analyzing particle size.
Microscopy can be used for characterizing the particle size in order to develop aerosol inhalers; this method is uniquely able to view and measure individual particles and provide quantitative and qualitative data about particle characteristics such as size and shape.
Automated instrumentation techniques can also be used to size large volumes of particles within a short period of time; however, these are not as effective in providing comprehensive observational details concerning the particles.
Laser diffraction, an automated instrumentation technique, is able to provide information on particle size distribution and can be useful for developing aerosols for inhalers. This type of particle analysis instrument involves the use of a laser that can be used over a sample and is diffracted by various sized particles that produce a diffraction light pattern. This measurement tool is able to measure particle sizes that are between 0.02 and 2000 micrometers and can gather data on how particle size distribution can affect products and processes, which can also have an effect on other factors such as reactivity and dissolution rate.
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While this method can be useful, it can only reflect the particle size at a primary level, which may not be a true reflection of what occurs when particles are deposited when used by patients in a real-life setting. This does not take into account any associated agglomeration that can occur after the drug particles are ejected out of an aerosol inhaler. However, utilizing other methods as well, such as microscopes and impactors that are able to test the inhalation of aerosols into sampling chambers, may be more effective.
Research into this area of science is significant for the development of effective aerosol inhalers, with various researchers utilizing different strategies. An example of this includes scanning electron microscopes, which have been researched for examining the particle size and size distribution of drugs delivered by MDIs.
In research in the Journal of Medical Science, researchers utilized an automated image analysis technique involving the dispersion of the particles from the aerosols into an Andersen cascade impactor for a simulation of particle behavior when the drug is inhaled.
This research was able to analyze particle size distribution using microscopical methods as well as strategies of improvement, which can be beneficial for pharmaceutical research into the development of various drugs.
Significance and Future Outlook
The optimum aerodynamic particle size distribution for aerosol inhalers has been noted to be between 1 and 5 micrometers; this is significant as aerodynamic particle size includes factors such as particle density and shape, which is also related to the physical particle size and volume equivalent diameter for a sphere, using a formula. The analysis of particle size can aid in developing aerosols for inhalers, which are best suited to carrying various drug formulations in order to result in effective absorption into tissues.
The size and distribution of particles within aerosols can reflect the deposition of the drug, and with further research into this area of science, the advancement in medicine can be furthered to ensure a high quality of treatment for patients with various respiratory diseases and disorders.
With 65 million sufferers of chronic obstructive pulmonary disease and three million deaths from this disorder per year, the requirement for innovative treatments for lung diseases is critical. The global impact of respiratory diseases has become a burden on healthcare systems and can affect quality of life; the analysis of particle size for the development of effective aerosol inhalers may aid in reducing this burden and enhance efficacy in patient treatment.
References and Further Reading
Who.int. 2022. The Global Impact of Respiratory Disease. [online] https://www.who.int/
Rawal, S. and Patel, M., 2018. Lipid nanoparticulate systems. Lipid Nanocarriers for Drug Targeting, pp.49-138. Available at: https://www.sciencedirect.com/science/article/pii/B9780128136874000025?via%3Dihub
Feddah, M. and Davies, N., 2003. Alternative Methods of Particle Size Analysis of Metered Dose Inhaler Aerosols. Journal of Medical Sciences, 4(1), pp.63-69. Available at: https://scialert.net/abstract/?doi=jms.2004.63.69
Abdo, R., Saadi, N., Hijazi, N. and Suleiman, Y., 2020. Quality control and testing evaluation of pharmaceutical aerosols. Drug Delivery Systems, pp.579-614. Available at: https://www.sciencedirect.com/science/article/pii/B9780128144879000120?via%3Dihub
Mitchell, J. and Nagel, M., 2022. Particle size analysis of aerosols from medicinal inhalers. [online] Jstage.jst.go.jp. Available at: <https://www.jstage.jst.go.jp/article/kona/22/0/22_2004010/_pdf/-char/en>
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