The invention relates to an activator unit for an autoinjector, capable of providing greater force compared to known activator units, in order for example to press a viscous drug through a cannula and/or to press a drug through a cannula that has a smaller diameter, thereby making operating an autoinjector more comfortable for the patient, wherein the activator unit for an autoinjector comprises: a substantially cylindrical housing； a spring unit including: a first coil spring, wherein a proximal end of the first coil spring directly abuts a proximal end of the substantially cylindrical housing, and wherein a distal end of the first coil spring directly abuts a spring adapter, and a second coil spring coaxial to the first coil spring, the second coil spring having a larger diameter than the first coil spring, wherein a proximal end of the second coil spring directly abuts the proximal end of the housing, and wherein a distal end of the second coil spring directly abuts the spring adapter； an axially movable piston positioned distal to the spring unit； and a retaining element connected to the piston and positioned within the spring unit, the retaining element having detent projections to lock the piston, wherein the piston is arranged counter to the spring unit and the retaining element.
