PROBLEM TO BE SOLVED: To provide an oral drug delivery system for controlled release of an active ingredient, being protected by a coating.SOLUTION: An oral drug delivery system is a tablet coated with one or more surfaces, having a core containing a layer containing an active ingredient composition (4), and a swelling composition layer (5, 6), and a coating (2) surrounding this core, the swelling composition layer being located in the immediate vicinity of one or more preselected surfaces of the coating. The coating contains i. a coating which contains a leachable component, and generates an imperfection in a moment by the component leaching due to a contact with aqueous environment, or ii. the coating including the imperfection (passage 3) which is an indent, a tear, a cut, or an etching which invades from the outer surface of the coating to the middle of the coating on one or more surfaces of the coating. The coating ruptures by the contact with the aqueous environment, and is removed fully from one or more surfaces which are located in the immediate vicinity of the swelling composition layer. And the coating is not removed from the other surfaces.【課題】剤皮で保護された、有効成分を制御放出する経口薬送達システムの提供。【解決手段】１つ以上の面を有する被覆された錠剤であり、有効成分組成物（４）を含有する層、及び膨潤性組成物層（５，６）、とを含む核、及び該核を囲む剤皮（２）を有しており、該膨潤性組成物層は、該剤皮の１つ以上の予め選択された面のごく近傍に位置し、該剤皮が、ｉ．浸出可能な成分を含み、水性環境との接触によって該成分が浸出することにより不完全性を瞬時に発生させる剤皮、あるいはｉｉ．該剤皮の１つ以上の面に、該剤皮の外側から始まり該剤皮の途中まで侵入するくぼみ、裂け目、切れ目、および溶蝕である不完全性（通路３）を含む剤皮であり、該剤皮が、水性環境との接触により破裂し、該膨潤性組成物層のごく近傍にある１つ以上の面から、完全に除去され、かつ、別の面からは除去されない経口薬送達システム。【選択図】図１
