DURECT can customize polymers to meet specific degradation requirements. The polymers and copolymers of glycolide, lactide, and ε-caprolactone degrade by simple hydrolysis. When exposed to aqueous media such as buffers or tissue, water is absorbed and reacts with the ester linkages, thus breaking the polymer backbone. One hydroxyl group and one carboxylic acid group forms for each ester linkage that is hydrolyzed. Because the ester linkages are cleaved randomly along the polymer backbone, relatively few water-soluble fragments form initially. Rather, long polymer chains are broken to form shorter ones. As a result, the reduction in molecular weight produces an increase in hydrophilicity but little change initially in physical properties or polymer mass. As degradation proceeds, however, the reduction in molecular weight leads to a reduction in physical properties and the formation of water-soluble fragments. These water-soluble fragments diffuse away from the polymer and are ultimately hydrolyzed to glycolic and lactic acids, which are processed through normal metabolic pathways. The rate of hydrolysis depends on factors such as the size and hydrophilicity of the particular polymer implant, the monomer composition and degree of crystallinity of the polymer, and the pH and temperature of the environment.