A cartridge syringe has a housing with an opening for inserting a cartridge having an cylinder filled with a medication and closed at its ends by a piercing membrane and a stopper having a blind hole. A ram is provided for pressing the stopper for injecting the medication in the cylinder after piercing the membrane. The ram has an actuating element and can be attached in the blind hole for aspiration. The ram has an outer sleeve with a core. The outer sleeve is displaceably guided in a rotatable manner and the core in a rotationally fixed manner. A front end of the outer sleeve is provided with at least one fixing hook which is spring-loaded inwardly. A cam is engageable with the fixing hook such that, upon rotation of the outer sleeve, the fixing hook is movable either to the fixing position or the unlocked position.
