Controlled release pharmaceutical tablet having lenticular form

Controlled release pharmaceutical tablet having a lenticular form consisting of three layers of which the central one or core (a) contains the active principle and the two outer layers or barriers (b) and (c) comprise gellable and/or erodible polymeric material, said barrier layers being equal or different among themselves for composition and/or thickness, while the central layer has a limited external annular surface exposed to the dissolution medium, through which the active principle is released.