a lipid or other hydrophobic or amphiphilic compound is integrated into a polymeric matrix for drug delivery to alter drug release kinetics . in embodiments where the drug is water soluble , the drug is released over longer periods of time as compared to release from the polymeric matrix not incorporating the hydrophobic compound into the polymeric material . in contrast to methods in which a surfactant or lipid is added as an excipient , the hydrophobic compound is actually integrated into the polymeric matrix , thereby modifying the diffusion of water into the microparticle and diffusion of solubilized drug out of the matrix . the integrated hydrophobic compound also prolongs degradation of hydrolytically unstable polymers forming the matrix , further delaying release of encapsulated drug .