Injection system

Injection system for preparing a mixture of a solvent and a medicament and for subsequent dosed injection of the mixture, the system comprising:

• a syringe from which set doses are apportioned from a cylinder ampoule having a first end closed by a pierceable membrane and a second end closed by a piston which can by a piston rod, which is successively advanced in a distal direction by the injection of set doses, be forced into the ampoule to press out a dose of a medicament stored in the ampoule between the membrane and the piston through an injection needle piercing the rubber membrane, wherein the piston rod has coupling means by which it is coupled to the piston of the ampoule to make this piston follow movements of the piston rod in both axial directions, and
• an ampoule with a piston which is provided with coupling means designed for co-operation with the coupling means of the piston rod of the syringe to secure said piston to said piston rod, and
• a needle mounted in a needle hub and having an injection part projecting from a distal side of the hub and a back needle piercing the membrane of an ampoule when the needle hub is mounted on the syringe.