EFFECT OF STORAGE ON THE STABILITY OF DL-PLA MICROSPHERES CONTAINING METHADONE

This work presents the changes in the characteristics of Dr-PLA micros pheres of different polymer molecular weights and cll-methadone conten ts, prepared by the solvent evaporation method, after a 3-year storage at room temperature (20 +/- 2 degrees C) under desiccated conditions. Size, shape and loading did not change, while degradation index (DI) increased during storage independently of the methadone content. The m ost stable polymers were those of weight average molecular weight 6300 0 and 33000. The mechanism involved in the polymer degradation dependi ng on the polymer molecular weight. The methadone release was evaluate d through dissolution efficiency (DE). The DE variation with time was kept in the +/- 20% range. (C) 1998 Elsevier Science B.V. All rights r eserved.