Autoinjector

An autoinjector, characterized in that it comprises:

• a reservoir module comprising a reservoir containing fluid and a piston, and including a needle;
• a driver module comprising:
• a body;
• a piston rod that co-operates with the piston of said reservoir, said piston rod being moved between a rest position and an injection position in which said piston rod has moved the piston of the reservoir so as to inject the fluid through said needle;
• an injection spring for urging said piston rod towards its injection position;
• and
• force control means, for causing the force exerted by said injection spring on said piston rod to vary in predetermined manner throughout the injection stage, said force control means comprising a lever and a cam, said lever being pivotally mounted at one end on said piston rod, being connected to said injection spring, and co-operating at its other end with said cam;
• and
• an interface module that is fastened to the driver module and that receives a reservoir module before each actuation, said interface module comprising a selector ring that is mounted to turn on the driver module, and pivot elements for fastening the reservoir module in the interface module.