Disclosed is a flowable composition which comprises: (a) a biodegradable thermoplastic polymer that is at least substantially insoluble in body fluid (such as a poly(DL-lactide-co-glycolide)), and wherein said biodegradable thermoplastic polymer is a polyester of one or more hydroxycarboxylic acids, or is a polyester of a combination of one or more diols and one or more dicarboxylic acids； (b) a biocompatible polar aprotic organic liquid that is highly water soluble and which comprises an amide, an ester, a carbonate, a ketone, an ether, a sulfonyl, or any combination thereof (and which is preferably selected from N-methyl-2-pyrrolidone, 2-pyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, caprolactam, or combinations thereof)； and (c) risperidone, 9-hydroxyrisperidone or a pharmaceutically acceptable organic or inorganic salt thereof； and wherein the flowable composition is an injectable subcutaneous formulation capable of forming a solid, microporous implant in a patient by diffusion of the biocompatible polar aprotic organic liquid out of the flowable composition into the body fluid, so that the flowable composition coagulates to form the implant.
