Abstract: This invention resides in the field of bioerodible polymers for use as drug delivery vehicles. In particular, this invention addresses means for controlling the rate of biodegradation and degradation in general of such polymers.

Abstract: Controlled-release particles containing biologically effective agents such as therapeutic drugs and local anesthetics are suspended in a liquid suspending vehicle which has an elevated viscosity, the viscosity being substantially higher than that of water. Preferred vehicles are non-aqueous liquids and aqueous media which contain a dissolved polymer to increase the viscosity of the vehicle. Regardless of the composition of the media, however, the increased viscosity permits the use of particles of a relatively large size without a loss of suspension stability or localized application. The large particles offer the advantage of a longer release profile, and thus more prolonged activity of the agent.