Method for preparing preparations having controlled release of an active component

DETAILED DESCRIPTION I claim: 1.
A process for producing a preparation comprising a plurality of granules each having a core and a unitary layer thereon containing at least one pharmaceutically active material which, on disintegration, release said pharmaceutically active material at a controlled rate, comprising applying to said cores in a continuous coating operation a solution or suspension containing at least one active compound and at least one pharmaceutically inactive release controlling substance over a period of time sufficient to cause said unitary layer of said active ingredient and inactive release controlling substance to form on each core to give granules of size 0.
3-2 mm, during said time period the concentration of active ingredient being decreased in the solution or suspension from which the layer is formed by adding additional release controlling substance to the solution or suspension, whereby there results granules each having a layer containing an active ingredient in which layer the concentration of active ingredient decreased radially outwardly from the core to the outer surface of said layer.
2.
A process according to claim 1, wherein said continuous coating is carried out by spraying said composition comprising active ingredient and inactive release controlling substance onto said core.
3.
A process according to claim 1, wherein the concentration of active ingredient in said solution or suspension decreases continuously with time, whereby the concentration of active ingredient in the layer on said core decreases continuously toward the surface thereof.
4.
A process according to claim 1, wherein the concentration of active ingredient in said solution or suspension is decreased during the time of coating in a discontinuous change, whereby a discontinuous gradient of concentration toward the surface of said layer is obtained.
5.
A process according to claim 1, wherein the inactive release controlling substance has lipophilic characteristics.
6.
A process according to claim 1, wherein said inactive release controlling substance is a water-soluble polymer