chapter  14
24 Pages

Physical Aging of Polymers and Its Effect on the Stability of Solid Oral Dosage Forms

Film coating is an effective method to modify drug release from tablets and pellets. Aqueous-based coating technology has become more popular due to environmental and regulatory requirements that restrict the use of organic solvents in production. The formation of thin, transparent lms from aqueous-based latex or pseudolatex dispersions occurs with the simultaneous evaporation of water [1,2]. Figure 14.1 is an illustration of lm formation from such systems. During the coating process (Stage I), water evaporates from the lm-coated substrate at a constant rate. The latex particles begin to pack together and fuse to form a continuous lm. As the colloidal particles begin to fuse and coalesce, as seen in Stage II, the rate of water evaporation decreases. By Stage III, lm formation is considered complete; however, it is during Stage III that changes occur in the drug-release rate due to physical aging of the polymeric lm coating.