A casing for an injection device of the type having a safety device which prevents operation of the device, incorporating an actuator means by which the safety means of the device can be actuated to allow operation of the device. Also a casing for a medicament container having an opening closed prior to use by a break-off tip, having relatively movable first and second casing parts, which on relative movement apply a breaking force to the break-off tip. A preferred embodiment includes both such features.