Patent ID: 7838028

Claim:
A pharmaceutical tablet system capable of prolonged floating in or on gastric fluid for releasing therein one or more pharmaceutically active substances in the course of an alternate succession of periods of substance release and no-release, said alternate succession having at least two periods of substance release separated by one period of no-release, whereby the tablet system is made up of a multilayered core placed in a cup-shaped envelope, the core is made up of release and no-release layers superposed in alternate succession to form a pile of layers that has at least two release layers flanking an intermediate no-release layer, each release layer being composed of pharmaceutically acceptable excipient and/or carrier having admixed thereto at least one of said pharmaceutically active substances, each no-release layer being composed of pharmaceutically acceptable excipient and/or carrier devoid of said pharmaceutically active substance, the cup-shaped envelope covers a bottom surface and side surfaces of the core placed therein while leaving exposed an upper surface of the core, characterized in that the cup-shaped envelope provides for buoyancy of the pharmaceutical tablet system with respect to gastric fluid by being formed of a compression-sintered mixture with voids, the mixture being comprised by buoyancy-providing materials in the form of a pharmaceutically acceptable hydrophobic material and a pharmaceutically acceptable inert powdered filler, the hydrophobic material being composed of fatty and/or waxy material capable of being sintered by compression and whose bulk density is lower than gastric fluid density, and the powdered filler having a loose powder density that is lower than gastric fluid density, the powdered filler consisting of magnesium aluminometasilicate; and the buoyancy-providing materials of the cup-shaped envelope being incorporated in the finished pharmaceutical tablet system in the range of 69 to 72 percent by weight.