Immediate and controlled release systems were prepared fitting a fast dissolution tablet in the hole of perforated matrices coated on all the surface excepting the hole. The release from the systems of a non steroidalanti-inflammatory drug, diclofenac sodium, was investigated both in water and in gastro-intestinal simulated flluids. A constant drug release was achieved after the complete dissolution of the tablet fitted in the hole. The dissolution of the initial dose was affected by the pH of the simulated gastric fluid. However, as the comparison with a sustained commercial product showed, a higher amount of drug was available from the system in thefirst 150 min
