CHARACTERIZATION OF CALCIUM FENOPROFEN .1. POWDER DISSOLUTION RATE AND DEGREE OF CRYSTALLINITY

Samples of calcium fenoprofen crystals have been prepared on laboratory, pilot and production scales, some by conventional aqueous precipitation, others under conditions designed to increase or decrease the degree of crystallinity. They were characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, surface area by nitrogen sorption, agglomerate size by Coulter counter, true density, sodium content, powder dissolution rates and heats of solution. No evidence of polymorphic variation was found. Most precipitation conditions gave partially fused agglomerates of primary crystals. Relative degrees of crystallinity were assessed from heats of solution. The more perfectly crystalline samples gave relatively high endothermic heats of solution coupled with low powder dissolution rates. Lattices with high levels of disruption, or low crystallinity, gave lower heats of solution coupled with enhanced powder dissolution rates. Heats of solution make a significant contribution to the overall characterization and to understanding batch-to-batch variation, and they relate well to the observed powder dissolution rates. © 1990.