Particle size characterization, pharmaceutical aerosols

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. 

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. 

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 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]. 

---