Abstract: Sustained release local anesthetic formulations are administered intra articularly and/or into body spaces/cavities. The formulation is preferably a plurality of injectable microparticles including a local anesthetic and an effective amount of a biocompatible, biodegradable, sustained release material prolonging the release of the local anesthetic and optionally and a pharmaceutically acceptable, i.e., non-toxic, augmenting agent effective to prolong the duration of the local anesthesia for a time period longer than that obtainable without the augmenting agent.