PROBLEM TO BE SOLVED: To provide a drug injection device having a reuse prevention function. Kind Code: A1 A drug injection device for injecting a fluid drug into a body, comprising a long insertion part to be inserted into the body from a tip side and a fluid drug stored inside the insertion part. A reservoir portion, an opening portion formed at the other end of the insertion portion and communicating with the reservoir portion, and a liquid medicine inserted into the reservoir portion through the opening portion to the distal end side of the insertion portion. A recess 10 for accommodating the rear end 11 of the piston is formed at the other end of the insertion part, and the recess 10 extends from the inner peripheral surface toward the inside of the recess. The piston includes a protruding projection 21 and the piston rear end portion 11 includes a piston fitting portion 22 that fits with the engaging projection 21. A drug injection device, which is formed so as to be irreversibly accommodated in the recess 10. [Selection diagram] Fig. 7【課題】再使用防止機能付きの薬剤注入器具を提供する。【解決手段】体内に流動性薬剤を注入する薬剤注入器具であって、先端部側から体内に挿入される長尺状の挿入部と、前記挿入部の内部に形成され、流動性薬剤が貯留される貯留部と、前記挿入部の他方端部に形成され前記貯留部と連通する開口部と、前記開口部を介して前記貯留部内に挿入され流動性薬剤を前記挿入部の先端部側に押し出すピストンとを備えており、前記挿入部の他方端部には、ピストンの後端部１１が収納可能な凹部１０が形成されており、凹部１０は、その内周面から凹部内側に向けて突出する係合突起２１を備え、ピストンの後端部１１は、係合突起２１と嵌合するピストン嵌合部２２を備えており、係合突起２１とピストン嵌合部２２との嵌合により、凹部１０内に不可逆的に収納可能に形成されていることを特徴とする薬剤注入器具。【選択図】図７
