The present invention provides a novel drug delivery system for the controlled release of therapeutically active substances at a predetermined, essentially constant release rate over a prolonged period of time. The delivery system comprises at least one core comprising said therapeutically active substance(s), at least one membrane encasing the core and an intermediary layer of a substantially inert material, wherein the intermediary layer is applied between the core and the membrane or between two membrane layers.本發明提供一種用於在延長時段內以基本上恆定之預定釋放速率控制釋放治療活性物質之新穎藥物遞送系統。該遞送系統包含至少一個包含該(該等)治療活性物質之核心、至少一個包覆該核心之膜及由實質上惰性之材料製成之中間層，其中該中間層係塗覆於該核心與該膜之間或塗覆於兩個膜層之間。
