Biodegradable controlled release microspheres for the prolonged administration of a local anesthetic agent, and a method for the manufacture thereof are disclosed. The microspheres are formed of a biodegradable polymer degrading significantly within a month, with at least 50% of the polymer degrading into non-toxic residues which are removed by the body within a two week period. Useful polymers include polyanhydrides, polylactic acid-glycolic acid copolymers and polyorthoesters containing a catalyst; polylactic acid-glycolic acid copolymers are preferred. Local anesthetics are incorporated into the polymer using a method that yields a uniform dispersion, preferably solvent casting. Prolonged release is obtained by incorporation of a glucocorticoid into the polymeric matrix or by co-administration of the glucocorticoid with the microspheres. The type of anesthetic and the quantity are selected based on the known pharmaceutical properties of these compounds.