The present invention concerns a prefilled syringe (400) with the typical tubular containment body (430), which extends along an axis between a front end element (420) and a rear end element (410), and wherein a fixed plug (470) and two sliding plugs (460, 450) are arranged. There is a bypass channel in the initial position of the syringe (400) between the first two plugs (470, 460). The two plugs (470, 460) form, together with a third plug (450) at the end of the syringe plunger, a first containment chamber (400L1) containing a first liquid substance and a second containment chamber (400L2) containing a second solid or liquid substance. In the prefilled syringe (400), the first plug (470):is arranged in a fixed position in contact with said front end element (420)；is provided with a non-through cavity (445) offset with respect to said axis and facing towards said front end element (420).本發明有關於一預充填注射器(400)，其具有一管狀密封體(430)，此管狀密封體(430)沿在一前端元件(420)與一後端元件(410)間之一軸延伸，其中一固定塞子(470)與兩可滑動塞子(460、450)擺置於此管狀密封體中。一旁路通道，於注射器(400)的初始位置時，位於注射器內固定塞子(470)與一可滑動塞子(460)間。固定塞子(470)、可滑動塞子(460)、與注射器中推桿之一端之可滑動塞子(450)之間，分別形成一第一容納腔(400L1)與一第二容納腔(400L2)。第一容納腔(400L1)容置一第一液體物質，第二容納腔(400L2)用於容置一第二固體或液體物質。在預充填注射器(400)中，第一塞子(470)擺置於一固定位置，接觸前端元件(420)，第一塞子(470)具有一非貫穿腔(445)，非貫穿腔(445)相對於中心軸間偏移，並面向於前端元件(420)。
