A medical injector, comprising: a body having a distal end and a proximal end; a plunger displaceably disposed in the body, the plunger having a plurality of spaced-apart ratchet teeth disposed along the length thereof, the plunger selectively displacing a stopper to dispense a medicament from said medical injector; an indexer disposed within the body to engage the plunger to permit distal displacement of the plunger and substantially prevent proximal displacement of the plunger; and an actuator comprising: a first actuator portion having an engagement portion to engage the plunger to permit proximal displacement of the actuator relative to the plunger and substantially prevent distal displacement of the actuator relative to the plunger; and a second actuator portion rotatably coupled to the first actuator portion to be rotatable relative thereto, characterized in that the second actuator is configured to, upon rotation of the second actuator portion relative to the body to a ready state, proximally displace the second actuator portion relative to the body in concert with non-rotatable proximal displacement of the first actuator portion and the engagement portion 50 relative to the plunger; wherein upon proximal displacement of the actuator relative to the body to a ready state, one or more of the ratchet teeth bypass the engagement portion to proximally displace the actuator relative to the plunger; and wherein upon distal displacement of the actuator relative to the body from the ready state, the actuator engages one or more of the ratchet teeth to distally displace the plunger relative to the indexer to distally displace the stopper to dispense medicament from the medical injector. a body having a distal end and a proximal end; a plunger displaceably disposed in the body, the plunger having a plurality of spaced-apart ratchet teeth disposed along the length thereof, the plunger selectively displacing a stopper to dispense a medicament from said medical injector; an indexer disposed within the body to engage the plunger to permit distal displacement of the plunger and substantially prevent proximal displacement of the plunger; and an actuator comprising: a first actuator portion having an engagement portion to engage the plunger to permit proximal displacement of the actuator relative to the plunger and substantially prevent distal displacement of the actuator relative to the plunger; and a second actuator portion rotatably coupled to the first actuator portion to be rotatable relative thereto, a first actuator portion having an engagement portion to engage the plunger to permit proximal displacement of the actuator relative to the plunger and substantially prevent distal displacement of the actuator relative to the plunger; and a second actuator portion rotatably coupled to the first actuator portion to be rotatable relative thereto, characterized in that the second actuator is configured to, upon rotation of the second actuator portion relative to the body to a ready state, proximally displace the second actuator portion relative to the body in concert with non-rotatable proximal displacement of the first actuator portion and the engagement portion 50 relative to the plunger; wherein upon proximal displacement of the actuator relative to the body to a ready state, one or more of the ratchet teeth bypass the engagement portion to proximally displace the actuator relative to the plunger; and wherein upon distal displacement of the actuator relative to the body from the ready state, the actuator engages one or more of the ratchet teeth to distally displace the plunger relative to the indexer to distally displace the stopper to dispense medicament from the medical injector.