Patent ID: 8187226

Claim:
An autoinjector comprising an outer housing in which is mounted a syringe, comprising: a barrel for holding a volume of medicament; a needle at one end of the barrel; and a plunger axially-moveable in the barrel; the autoinjector further comprising an inner housing intermediate the outer housing and the syringe and an energy source in communication with said inner housing, wherein the inner housing comprises one or more radially-flexible tags, wherein the one or more radially-flexible tags are moveable radially into and out of communication with the plunger, wherein the inner housing is moveable by the energy source between three positions, namely a first position in which the inner housing is in communication with the barrel such that, in use, the plunger and barrel are moveable axially so as to move at least part of said needle out of the outer housing; a second position in which the inner housing is in communication with the plunger but not the barrel such that, in use, said plunger is moveable axially into said barrel so as to expel medicament through the needle; and a third position in which the inner housing is in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing, characterised in that the autoinjector further comprises means associated with a rear flange of said plunger providing a plurality of axial positions at which it is possible for said inner housing to engage said plunger in said second position.