Pharmaceutical aerosols, characterization

Drug delivery to the respiratory tract has been characterized in the past decade by an increase in knowledge of drug droplet or particle manufacture, behavior, aerosol dispersion, lung deposition and clearance. The number of diseases for which aerosol therapy may be applicable has increased dramatically. The pharmaceutical scientist is no longer limited to pulmonary diseases as therapeutic targets. Substantial progress has been made in every area of pharmaceutical aerosol science, and it is anticipated that this will ultimately lead to many new therapies. 

Glover, W. Chan, H.-K. Electrostatic charge characterization of pharmaceutical aerosols using electrical low-pressure impaction (ELPI). J. Aerosol Sci. 2004, 35 (6), 755-764. 

The following sections focus on the principles of collection and characterization of pharmaceutical aerosols. Instruments have been selected to illustrate the methods that they typify. 

A wide variety of methods have been used to measure the particle size of aerosols, and most of these have found an application in the specialized field of pharmaceutical product characterization. In general, these approaches result in the measurement of a particular diameter that may be defined according to the principle underlying the measurement [3]. 

There has been significant research in the area of particle size characterization of pharmaceutical aerosols since the early 1990s. The focus has been not only on methods but on data presentation, analysis, and requirements for regulatory submissions. 

Fults K, Cyr TD, Hickey AJ. Characterization of pharmaceutical aerosols using inertial collection devices. Presented at Proceedings of the Second World Congress on Particle Technology, Kyoto, Japan, 1990. 

As described above, inertial cascade impaction is the gold standard for characterization of pharmaceutical aerosols. However, it is not the only method avail-... 

CA Dunbar, AJ Hickey, P Holzner. Dispersion and characterization of pharmaceutical dry powder aerosols. KONA 16 7 14, 1998. 

MDI products are subject to batch control and acceptance tests similar to those for other pharmaceutical dosage forms, that is, active drug identification, dose delivery, and dose uniformity. Additional special tests unique to inhalers, e.g., characterizing the particle size distribution of the delivered aerosol, are also applied. Typical tests are shown in Table 3. 

A reappraisal of the particle size characterization of pharmaceutically relevant materials, including therapeutic aerosols, was advocated in the late 1980s [1], This led to a reevaluation of compendial standards for particle size measurement [2], By the late 1990s most pharmacopoeia had adopted new standards for the testing of inhalation aerosols. 

Park C-W, Li X, Vogt FG et al. (2013) Advanced spray-dried design, physicochemical characterization, and aerosol dispersion performance of vancomycin and clarithromycin multifunctional controlled release particles for targeted respiratory delivery as dry powder inhalation aerosols. International Journal of Pharmaceutics 455 374—392. 

Different types of dispersions are encountered in industrial applications, the most common ones include solid/liquid (suspension), liquid/liquid (emulsions), gas/liquid (foams), liquid/solid (gels), and liquid/gas (aerosols). These dispersions are encountered in almost every industry in some form or the other during the preparation or as end product. Examples of industrial applications of dispersions include paints, dyestuffs, printing ink, paper coatings, cosmetics, ceramics, microelectronics, agrochemical and pharmaceutical formulations, and various household products. In the following sections, the characterization and properties of solid/liquid suspensions will be described. However, the same concepts would be valid for other kinds of dispersions also. 

Aerosols. Aerosol size characterization is a highly specialized science in its own right and has significance for drug delivery, environmental concerns-including production of pharmaceutical and electronic products- and areas such as chemical and biological warfare. Except to observe that many of the sizing... 

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