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Filling the Pharmacopeial Gaps of Visual Inspection Toward Standardization and Consistency of Visible Particle Testing



Linda Narhi, George M. Bou-Assaf, Kristen Gonzalez, Maryam Mazaheri, Steven Messick, Srivalli Telikepalli


The presence of visible particles that are not anticipated to be present in drug products is one of the most common causes of recalls, and warning letters1, 2. This critical quality attribute, which is typically determined during visual inspection (along with defects in the container closure system), must be controlled to minimize its occurrence in all drug products. Conditions for visual inspection of visible particles in parenteral solutions, including the amount of light used to illuminate the sample, the black and white background against which inspection should be performed, and the amount of time allowed for the inspection, are addressed in the pharmacopeia. However, the determination of many parameters and operational conditions are left to the discretion of individual manufacturers and end users. These include the size of the particles detected and defined as visible, the training set and procedure used to train the human inspectors, and the interpretation of results. Consequently, we observe variability among organizations in the stringency of the method and the limits applied, as well as inconsistency between sites, contract manufacturing organizations (CMO), and products within a single organization. In this article, we discuss the current state of visible particle assessment and propose a new USP chapter focused on assay suitability, enabled by universally available standards, that would fill the current pharmacopeial gaps, and result in a universal, consistent definition of visible particles and the method by which they are analyzed.
United States Pharmacopeial Forum


Narhi, L. , Bou-Assaf, G. , Gonzalez, K. , Mazaheri, M. , Messick, S. and Telikepalli, S. (2021), Filling the Pharmacopeial Gaps of Visual Inspection Toward Standardization and Consistency of Visible Particle Testing, United States Pharmacopeial Forum (Accessed June 16, 2024)


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Created May 3, 2021, Updated October 12, 2022