An injection device comprising: a housing adapted to receive a syringe having a reservoir portion and a discharge nozzle, so that the syringe is movable between a retracted position in which the discharge nozzle is contained within the housing and an extended position in which the discharge nozzle extends from the housing through an exit aperture; a drive that acts upon the syringe to advance it from its retracted position to its extended position and discharge its contents through the discharge nozzle; a removable cap adapted to be connected to the housing for closing the exit aperture; and a syringe carrier for carrying the syringe as it is advanced, wherein the syringe carrier comprises a sheath for surrounding the reservoir portion of the syringe, wherein the sheath has a first internal diameter along its length, and an intermediate section with a second internal diameter which is smaller than the first internal diameter so that a first end of the sheath is adapted to support the syringe between the reservoir portion and the discharge nozzle and prevent forward movement of the syringe in the syringe carrier, and characterised in that the removable cap is adapted to restrict movement of the syringe carrier in a direction towards the exit aperture when the removable cap is connected to the housing, wherein the cap provides a first interface for restricting movement of the syringe carrier in a direction towards the exit aperture and the syringe carrier provides a second interface that engages the first interface when the removable cap is connected to the housing, wherein the first interface and second interface each comprise a planar surface. a housing adapted to receive a syringe having a reservoir portion and a discharge nozzle, so that the syringe is movable between a retracted position in which the discharge nozzle is contained within the housing and an extended position in which the discharge nozzle extends from the housing through an exit aperture; a drive that acts upon the syringe to advance it from its retracted position to its extended position and discharge its contents through the discharge nozzle; a removable cap adapted to be connected to the housing for closing the exit aperture; and a syringe carrier for carrying the syringe as it is advanced, wherein the syringe carrier comprises a sheath for surrounding the reservoir portion of the syringe, wherein the sheath has a first internal diameter along its length, and an intermediate section with a second internal diameter which is smaller than the first internal diameter so that a first end of the sheath is adapted to support the syringe between the reservoir portion and the discharge nozzle and prevent forward movement of the syringe in the syringe carrier, and characterised in that the removable cap is adapted to restrict movement of the syringe carrier in a direction towards the exit aperture when the removable cap is connected to the housing, wherein the cap provides a first interface for restricting movement of the syringe carrier in a direction towards the exit aperture and the syringe carrier provides a second interface that engages the first interface when the removable cap is connected to the housing, wherein the first interface and second interface each comprise a planar surface.