Drug delivery from catalysed erodible polymeric matrices of poly(ortho ester)s.

The incorporation of small amounts of acid anhydrides into hydrophobic poly(ortho ester)s can facilitate the erosion and drug release from delivery systems. Since the reaction can be controlled by the amount of anhydride employed, the reaction is confined to a small reaction zone near the surface and constant delivery rates can be achieved. The catalytic activity is negatively correlated with the pKa of the corresponding acid of the anhydride.