Patent ID: 6083533
Filing Date: 2000-07-04
Classification: A61K

Abstract:
A process for producing a layered tablet for the controlled release of at least one active substance in a liquid, said tablet comprising at least one active substance-containing layered matrix having an active substance releasing surface when contacting the liquid medium, said releasing surface being provided, at least partially, with a cover layer which delays or prevents the active substance release wherein:a) the active substance-containing layer matrix is a formed body which is prestressed, has thickness gradients and is formed from a powder or granulate of an active substance-containing substrate,b) the cover layer is an additional layer which has thickness gradients and is formed from a powder or granulate of a substrate, which is erodible in the liquid medium, by pressing the cover layer onto the releasing surface of the matrix, andc) the thickness gradients of the cover layer controlling the active substance release rate are predetermined by the shape of the matrix layer, the direction of the thickness gradient of the matrix being complementary to the direction of the thickness gradients of the cover layer,wherein said process comprises:1) inserting the active substance-containing matrix layer in the form of a prefabricated pressed piece into a die of a tableting machine, and2) compressing the prefabricated pressed piece into a layered tablet under the addition of a powder or granular material for the cover layer.