A fluid composition comprising: a biodegradable thermoplastic polyester polymer that is at least substantially insoluble in body fluid； a terminal biocompatible protected oligomeric liquid； and a bioactive agent, a metabolite or a prodrug thereof, in which the terminal biocompatible protected oligomeric liquid is of formula I, II, III, IV or V: ** Formula ** in which: each R1 is, so independent, (C1-C12) alkyl or (C1-C12) alkylcarbonyl (C1-C12) alkyl； each R2 is, independently, (C1-C12) alkyl, carbonyl (C1-C12) alkyl or (C1-C12) alkyl ester； each R3 is independently alkylene (C1-C12)； R4 is (C1-C12) alkylene, carbonyl (C1-C12) alkylcarbonyl or (C3-C12) cycloalkadiyl； R5 is alcatriyl (C1-C12) or cycloalcatriyl (C3-C12)； R6 is (C1-C12) alkylene, (C1-C12) alkyne, cycloalcadiyl (C3-C12), alktriyl (C1-C12) or cycloalcatriyl (C3-C12)； R7 is (C1-C12) alkylene or (C1-C12) alktriyl, X is absent or is oxygen； W is absent, or is carbonyl or carbonyloxy； and any alkyl or alkylene of R1, R2, R3, R4, R5, R6 and R7 may optionally be substituted on the carbon with one or more oxo, halogen, nitro, cyano, (C1-C12) alkyl, (C1-C6 alkoxy) ), trifluoromethyl, and be optionally interrupted in the carbon with one or more oxy, imino or thio, and be optionally partially unsaturated； and each a, b, c and d is, independently, 0, 1, 2, 3, 4 or 5.Una composición fluida que comprende: un polímero de poliéster termoplástico biodegradable que es al menos sustancialmente insoluble en fluido corporal； un líquido oligomérico protegido terminalmente biocompatible； y un agente bioactivo, un metabolito o un profármaco del mismo, en la que el líquido oligomérico protegido terminalmente biocompatible es de fórmula I, II, III, IV o V:**Fórmula** en las que: cada R1 es, de manera independiente, alquilo (C1-C12) o alquiléster (C1-C12) alquilencarboxílico (C1-C12)； cada R2 es, de manera independiente, alquilo (C1-C12), carbonil-alquilo (C1-C12) o alquiléster (C1-C12) carboxílico； cada R3 es, de manera independ
