ABSTRACT
This chapter outlines the main elements of erodible controlled-release systems. The drugs contained in these systems may be released either by degradation of the polymer matrix or by hydrolytic cleavage of the polymer-drug bonds. Two main classes are: erodible systems and drug-polymer conjugates. In this chapter, the prefix "bio-" used with one of the foregoing terms indicates that the process occurs within a biological environment. In an erodible system, solubilization of the solid polymer occurs as a consequence of a chemical reaction, dissolution of a water-soluble polymer, ionization, or protonation. Many polymers are referred to as erodible, degradable, and absorbable, these terms often being used interchangeably in the literature. Both heterogeneous and homogeneous erosion represent extreme cases. Most erodible drug delivery systems are combinations of the two processes. The chapter highlights the characteristics of some of the more widely studied families of erodible polymers.
