PT  - JOURNAL ARTICLE
AU  - Williams, N. A.
AU  - Polli, G. P.
TI  - The Lyophilization of Pharmaceuticals: A Literature Review
DP  - 1984 Mar 01
TA  - PDA Journal of Pharmaceutical Science and Technology
PG  - 48--60
VI  - 38
IP  - 2
4099  - http://journal.pda.org/content/38/2/48.short
4100  - http://journal.pda.org/content/38/2/48.full
SO  - PDA J Pharm Sci Technol1984 Mar 01; 38
AB  - The freeze-drying of pharmaceutical products is discussed in successive stages involving the freezing of the product, the sublimation of ice (primary drying) and the desorption of water (secondary drying) from the product. The factors influencing the physical characteristics of the end product and the drying rate, e.g., freezing pattern and chamber pressure, are discussed in detail. Methods for studying the freezing characteristics of drug solutions, namely thermal analysis, resistance measurements, D2 analysis and microscopy, are described. The primary drying stage is influenced by external factors such as chamber pressure and shelf temperature, and by internal factors such as concentration and the degree of crystallization of the water in the sample. Methods for determining the end point of secondary drying and some problems often encountered (including those concerned with the equipment) in freeze-drying are discussed.