Freezing and Annealing Phenomena in Lyophilization

INTRODUCTION The freezing step of lyophilization is of paramount importance. It is the principal dehydration step, and it determines the morphology and pore sizes of the ice and product phases. In general, the desired attributes of a lyophilized product aren consistent high yield of product activity through lyophilization, n appropriate crystallization (or not) of product and excipient(s), n glass transition temperature higher than the desired storage temperature(related directly to residual moisture level), n pharmaceutically elegant, mechanically strong cake, n rapid reconstitution, n short, consistent, and robust freeze-drying cycle, and n stability of all product quality attributes through the intended shelf-life.