An injection device for delivering a dose of medicament from a syringe (5), the injection device comprising a housing (10), a plunger (210) moveably mounted within the housing (10), an actuation mechanism (200), a trigger mechanism (40), and a plunger velocity regulator. The actuation (mechanism (100) is arranged to provide a forward biasing force to urge the plunger (210) forward in use to express a dose of medicament, and the trigger mechanism (40) is arranged to releasably hold the plunger (210) against the force of the actuation mechanism (200). The plunger velocity regulator comprises a cam surface (262) associated with the housing, and a cam member (252) associated with the plunger (210) and arranged to engage the cam surface (262) during actuation movement of the plunger (210) such that axial movement of the plunger (210) relative to the housing (10) causes relative rotational movement of the cam member (252) which limits the forward velocity of the plunger movement. The plunger (210) is axially connected to the cam member (252) by a releasable coupling (300), and the plunger velocity regulator further comprises a coupling member (350) which blocks release of the releasable coupling (300) when the plunger (210) is in a rearward position and wherein forward movement of the plunger (210) moves the releasable coupling (300) out of engagement with the coupling member (350) such that the plunger (210) may disengage the cam member (252) after an initial movement of the plunger (210).L'invention concerne un dispositif d'injection permettant administrer une dose de médicament à partir d'une seringue (5), le dispositif d'injection comprenant un boîtier (10), un piston (210) monté de façon à l'intérieur du boîtier (10), un mécanisme d'actionnement (200), un mécanisme de déclenchement (40), et un régulateur de vitesse de piston. Le mécanisme d'actionnement (100) est conçu pour fournir une force de sollicitation vers l'avant afin de pousser le piston (210) vers l'avant l
