A water soluble, biodegradable ABA- or BAB-type tri-block polymer is disclos ed that is made up of a major amount of a hydrophobic A polymer block made of a biodegradable polyester and a minor amount of a hydrophilic polyethylene glycol(PEG) B polymer block, having an overall average molecular weight of between about 2000 and 4990, and that possesses reverse thermal gelation properties. Effective concentrations of the tri-block polymer and a drug may be uniformly contained in an aqueous phase to form a drug delivery composition. At temperatures below the gelation temperature of the tri-block polymer the composition is a liquid and at temperatures at or above the gelation temperature the composition is a gel or semi-solid. The composition may be administered to a warm-blooded animal as a liquid by parenteral, ocular, topical, inhalation, transdermal, vaginal, transurethral, rectal, nasal, oral, pulmonary or aural delivery means and is a gel at body temperature. The composition may also be administered as a gel. The drug is released at a controlled rate from the gel which biodegrades into non-toxic products. The release rate of the drug may be adjusted by changing various parameters such as hydrophobic/hydrophilic component content, polymer concentration, molecular weight and polydispersity of the tri-block polymer. Because the tri-block polymer is amphiphilic, it functions to increase the solubility and/or stability of drugs in the composition.Vannløselig, bionedbrytbar ABA- eller BAB-triblokkpolymer hvor en største mengde utgjøres av en hydrofob A-polymerblokk dannet av en bionedbrytbar polyester, og en mindre mengde utgjøres av en hydrofil polyetylen-glykol (PEG) som B-polymerblokk. Polymerens totale midlere molekylvekt er mellom 2000 og 4990, og den har reversible termiske gelingsegenskaper. Triblokkpolymeren og et medikament jevnt fordelt i en vannfase, danner en medikamentleverende blanding. Under triblokkpolymerens gelingstemperatur er blandingen en væske,
