biodegradable microspheres in controlled release and their method of preparation.

Method for the preparation of a pharmaceutical composition in the form of microspheres controllably releasing at least one water soluble active ingredient. The method comprises the steps of dissolving the active ingredient in a suitable quantity of water; emulsifying the aqueous solution containing the active ingredient with a solution of at least a d,l-lactide-co-glycolide-type matrix copolymer in chlorinated hydrocarbon further containing a low molecular weight polyactide release modulating agent, which results in a first microfine and homogeneous emulsion; emulsifying the first emulsion thus obtained in an external aqueous phase, containing a surface active agent; and removing and evaporating the solvent to produce microspheres which are recovered after filtering, washing and drying.