An injection device includes a forward housing, a drive housing that has a forward end configured to be attached to and detached from a rear end of the forward housing, a syringe holder mounted within the forward housing for longitudinal movement with respect to the forward housing, and a syringe with a needle that is mounted in the syringe holder. The drive housing includes a drive mechanism, and the syringe holder includes detent means for engaging the syringe to prevent or limit relative axial movement of the syringe relative to the syringe holder.
