Therapeutic system for controlled release of drugs

A new modular delivery system is described, which is able to release the vehicled active ingredient at controlled rate and for a predetermined period of time. The new system is characterized by: 1. Dosage units obtained by compression comprising natural and/or synthetic, hydrophilic, biocompatible polymers, capable to swell on contact with water or aqueous fluids thus providing a swelling pressure, containing a therapeutically active dose of drug or fractions thereof, 2. A polymeric barrier coated on said units, which will break because of units volume increase after their contact with water, and controlling the fluids entrance within the system and, therefore, the core swelling. The active ingredient release is almost complete, and it may occur according to zero-order kinetics without insoluble residues of appreciable extent. A process for preparing said system is also described.