an improved biodegradable controlled release system consisting of a polymeric matrix incorporating a local anesthetic for the prolonged administration of the local anesthetic agent , and a method for the manufacture thereof , are disclosed . the polymers and method of manufacture used to form the plams are selected on the basis of their degradation profiles : release of the topical anesthetic in a linear , controlled manner over a period of preferably two weeks and degradation in vivo with a half - life of less than six months , more preferably two weeks , to avoid localized inflammation . alternatively , a non - inflammatory can be incorporated into the polymer with the local anesthetic to prevent inflammation .