Image analysis for particle characterization

Regulatory agencies recognize the benefits of visual analysis for the evaluation of inhalation formulations. US Pharmacopoeia chapter approves of microscopy for determination of the number of large particles, agglomerates, and foreign particulates in MDI emissions. In addition, an FDA draft guidance document suggests that the use of the microscope “has certain merits and, therefore, should be retained for release and stability purposes,” particularly control and monitoring of morphic form changes on stability. Microscopy also provides useful information for early characterization of drug substance and the evaluation of crystal growth and agglomeration during temperature cycling studies.