Method evaluation: automated microscopy as a compendial test for particulates in parenteral solutions.

Accurate enumeration and sizing of contaminant particles in parenteral solutions are critical to the assessment of product quality and suitability for patient use. Current manual microscopic and instrumental (light obscuration) methodologies specified by the USP both result in data of high variability. The microscopic assay for large volume parenterals is time consuming and incorporates an undesirable level of subjectivity; light obscuration counters tend to undersize larger particles and fibers and have low detection efficiency for some particle types commonly present in small volume injections. Light microscopic image analysis is proposed as a method which combines the best features of the two present methods and allows an accurate, precise, and cost effective analysis of parenteral contaminant particles. This paper briefly summarizes the principles of microscopic image analysis and discusses its application in concert with optimized sampling and counting techniques as an improved compendial methodology. Instrument performance requirements are discussed with reference to a number of currently available image analysis systems.