Pharmaceutical Technology: Controlled Drug Release, Volume 2

12
Biodegradable polymers: Effect of thermal treatment on the
physicomechanical and dissolution properties of compacts
Marcelo O.Omelczuk
Drug Dynamics Institute, College of Pharmacy, The University of Texas at Austin,
Austin, TX 78712–1074 USA
Kuei-Tu Chang
Sterling-Winthrop Research Institute, Rensselaer, NY 12144–3493 NY and
James W.McGinity
Drug Dynamics Institute, College of Pharmacy, The University of Texas at Austin,
Austin, TX 78712–1074 USA
SUMMARY
Biodegradable polymers, such as poly(lactic acid) and poly(caprolactone), were investigated as
binders in the formulation of matrix tablets for controlled release. Polymers of different stereo
configuration and molecular weights were incorporated into tablet formulations containing the
model drug theophylline in combination with excipients such as microcrystalline cellulose. It was
shown that thermal treatment of these tablets above the glass transition temperature of the
polymer accelerated, retarded or had an insignificant effect on the dissolution release rate of
theophylline from the compact, as compared with the non-thermally treated tablets.
INTRODUCTION
Polymers, such as poly(lactic acid) and poly(caprolactone), have been classified as being
biocompatible or biodegradable. In vivo, these polymers eventually undergo hydrolytic scission,
producing by products which can be metabolically handled by the body. For example, poly(lactic
acid) is susceptible to hydrolytic de-esterification to lactic acid, a normal metabolite in the glycolytic
in carbohydrate metabolism [1,2]. Other important properties include their non-toxicity,
sterilizability and stability. These polymers can also be cast into films and are completely miscible
with many other polymers and plasticizers. Perhaps the most important characteristic is that they
can be synthetically engineered to produce desirable chemical, physical and mechanical
properties. To date, most of these polymers have been investigated for use in surgical repair
materials [1,3]. Other promising areas of application have involved the use of these polymers in
developing systems for implication, injection, and insertion [2,5–7]. The use of these polymers in