The invention provides an injection device comprising a housing, a plunger 110 moveably mounted within the housing, an actuation mechanism arranged urge the plunger forward to express a dose of medicament, and a trigger mechanism arranged to (directly or indirectly) releaseably hold the plunger against the force of the actuation mechanism. The injection device further comprises a plunger velocity regulator 160 comprising a cam surface 162a associated with one of the housing or the plunger, and a cam member 152a associated with the other of the plunger or the housing, the cam member being arranged to engage the cam surface after triggering movement of the plunger such that axial movement of the plunger relative to the housing causes rotational movement of the cam member, thus limiting the forward velocity of the plunger movement. The cam may follow a helical track.
