ABSTRACT
Freeze drying, or lyophilization, is an important pharmaceutical process that allows for the preservation of heat-sensitive drugs and biologicals. The most common application of freeze drying in the pharmaceutical industry is in the manufacture of injectable products. Freeze drying was introduced as a practical commercial process about the time of World War II for the preservation of blood plasma. The shelves of the freeze dryer contain internal channels with circulating silicone oil or another suitable heat transfer fluid. The most important objective in developing a freeze dried product is to assure that the product quality is maintained throughout the shelf life. The eutectic temperature is important in the freeze drying process because it represents the maximum allowable product temperature during primary drying. The most visual method for characterizing the freezing and freeze drying behavior of a formulation is by direct observation under a microscope.
