The distribution of water in degrading polyglycolide. Part I: Sample size and drug release

The effect of sample thickness on the degradation of polyglycolide (PGA) disks and on their drug release profiles is explored in this paper, and conclusions drawn about the distribution of water across a sample during degradation. The degradation process was monitored by measuring changes in the long period calculated from small angle X-ray scattering profiles, and by following changes in the pH of the buffer solutions. Drug release profiles were obtained using UV-spectrophotometry. The measurements suggest that reaction-erosion fronts form at the surface of all samples after around 7 days of degradation, and that these fronts progress through the sample at a constant rate of 0.032 mm/day. The data are consistent with a model in which drug is released quickly from the porous, hydrated regions behind the front, and reaches 100% release when the fronts meet. (C) 2003 Kluwer Academic Publisher.