Pharmaceutical composition made of microparticles for the slow release of anactive substance at least during a period covering the 6th month after injectionof said composition, said composition comprising a group of microparticlesmade of a copolymer of the PLGA type which incorporate an active substance in theform of a water insoluble peptide salt； said copolymer furthermore comprisingat least 75 % of lactic acid and an inherent viscosity between 0.1 and 0.9 dl/g,as measured in chloroform at 25 °C and at a polymer concentration of 0.5 g/dL；said microparticles furthermore having a size distribution defined as follows: - D (v,0.1 ) is between 10 and 30 micrometers, - D (v,0.5) is between 30 and 70 micrometers,- D(v,0.9) is between 50 and 1 10 micrometers.
