Particle size distributions of inert spheres and pelletized pharmaceutical products by image analysis.

Image analysis was used to measure particle size distributions (PSDs) of ensembles of 425 to 1400 microm-size materials. Repeatability of a measurement, suitable sample sizes, and methods of sampling were assessed. Two lots of inert spheres were compared prior to drug layering in a Glatt GPCG-5 rotor. The differences in PSD in the starting materials were reflected in the rotor-granulated products. Such detailed information was not available from sieving with U.S. standard wire mesh sieves. The products from the rotor process were polymer-coated in a Wurster process in a Glatt GPCG-3, 4-in. Wurster. The resolution of the technique was sufficient to measure differences in diameter equating to 4-microm coat thickness, which resulted from applying 2% polymer coat weight. The utility of the technique for monitoring commercial scale processes was demonstrated by measuring diameter after layering drug onto nonpareils in a Glatt RG-150 rotor, and by measuring the diameter after application of a polymer solution in a Glatt 46-in. Wurster coating process. The similarity of samples removed from the sample port in situ and samples from the batch suggested that processes in the fluid bed are intensively mixed and inherently random.