The most important physicochemical parameter influencing the deposition of aerosols in the lungs is particle or droplet size. Consequently, it is necessary to understand the principles and the methods of estimating particle size, allowing meaningful interpretation of the data. In addition, therapeutic effect is related to the mass of particles having a specific size, which relates to the distribution of particles in a range of sizes fully describing the aerosol.

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.

Particle size analysis of pharmaceutical aerosols has a strong foundation based on other disciplines. Most of the analytical techniques used were in existence before the development of the modern pharmaceutical aerosol dosage form. However, some significant challenges have to be overcome in the use of these techniques for assessing pharmaceutical systems.

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.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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