The invention relates to a delivery system for the sustained and controlleddelivery of a group of bioactive agents. More particularly, the inventionrelates to a delivery system and a method for delivery of a bioactive agentcontaining a nucleophilic functional group by means of a biodegradable,sustained-release implant. The implant may be a preformed implant,microparticles or an in situ formed implant. The implant includes abiodegradable thermoplastic polymer, the bioactive agent having a nucleophilicgroup substituent and a stabilizing associate as well as other optionalcomponents. The combination of the stabilizing associate with the bioactiveagent prevents and/or minimizes and/or lessens degradation of thethermoplastic polymer by the bioactive agent.
