SELECTABLE DOSE INJECTION DEVICE WITH LATCH MECHANISM

A substance delivery device for delivering a substance from a container includes a body, and a plunger movable with respect to the body so as to expel at least a portion of a substance from the container, a trigger mechanism, a latch member latched in a stationary position at least along the longitudinal axis of the device before use, and a lockout shroud movable along the longitudinal axis relative to the latch mechanism. User manipulation of the trigger mechanism causes the latch mechanism to become unlatched and move along the longitudinal axis and to cause movement of a plunger relative to the body, and in a first position of the lockout shroud along the longitudinal axis relative to the latch member, the lockout shroud prevents the trigger mechanism from unlatching the latch member, whereas in a second position the lockout shroud allows the trigger mechanism to unlatch the latch member.