Abstract

The purpose of this chapter is to introduce the major concepts and applications of cooling and congealing processes in the pharmaceutical industry. A cooling and congealing process must follow any process involving a melt. The melt-congealing technique has been practiced in the manufacture of wax-based suppositories for over 100 years. New applications have evolved quickly in the last 50 years to meet the increasing need for improving the solubility and consequent bioavailability of poorly water-soluble drugs and making modified-release drug products. Solid dispersions, matrix tablets, and coated drug-laden beads are some common examples. One of the methods of preparing solid dispersions is melt congealing. The basic concept and process required to form solid dispersions of poorly water-soluble drugs in solid matrices are attributed to the work of Sekiguchi and Obi in 1961 (1). They melted a sulfathiazole-urea mixture of eutectic composition at above its eutectic temperature, solidified the dispersion in an ice bath, and pulverized it into a powder. A modification of the process involves spray congealing from a modified spray dryer onto coated metal surfaces and has been used for dispersions containing mannitol (2). Hot-melt coating and granulation processes have also been used in the development of wax-coated or wax-based matrix sustained-release products.