PROBLEM TO BE SOLVED: To provide a prefilled syringe having an external cylinder and enabling easy and precise visual identification of whether the prefilled syringe is unused or used.SOLUTION: A prefilled syringe 1 is provided with: an injection cylinder 10 that includes an injection cylinder main body 40 and an external cylinder 30 that extends from an insertion port of the injection cylinder main body 40 toward a base end side and has an opening at a base end a cap 24 a gasket 51 and a plunger 50 that slides the gasket 51 by a pressing force to a pressing part 58 of the base end of a shaft part 52 to discharge a liquid medicine 42 in the injection cylinder main body. The external cylinder 30 is provided, at the wall part thereof, with a window 34 and a mask part 35 that conceals an inside of the external cylinder 30, and the shaft part 52 is provided, at a part thereof, with a mark part 54 larger than an inner diameter of the injection cylinder main body and having an outer peripheral surface of a color different from that of other part in such a manner that: before discharging the liquid medicine, the mark part is covered by the mask part, and thus it is not possible to visually recognize the mark part through the window and after completing the discharging of the liquid, the outer peripheral surface of the mark part becomes visually recognizable through the window along with movement of the plunger.COPYRIGHT: (C)2016,JPO&INPIT【課題】外筒を有し、プレフィルドシリンジの未使用・使用済を、目視で簡便かつ確実に識別できるプレフィルドシリンジを提供する。【解決手段】注射筒本体40とその挿入口部の周囲から基端側に延び、基端に開口部とを有する外筒30を備える注射筒10と、キャップ24と、ガスケット51と、軸部52の基端の押圧部58への押圧によってガスケット51を摺動させて、注射筒本体内の薬液42を排出させるプランジャ50とを、具備するプレフィルドシリンジ1であって、外筒30の壁部に、窓部34と外筒30の内部を隠すマスク部35とを有し、軸部52の一部分に、注射筒本体の内径よりも大きく外周面の色がプランジャ50の他の部分とは異なる色の目印部54を有し、薬液の排出前は、目印部がマスク部に覆われ窓部を通して目印部が視認できず、薬液の排出完了時は、プランジャの移動に伴い目印部の外周面が窓部から視認可能となるものである。【選択図】図1
