An autoinjector device comprises an elongate housing (10)containing a syringe or cartridge (12)having an internal piston for expressing a dose from the syringe or cartridge. A drive mechanism includes a drive member (18) for engaging said piston and a drive spring (20) or the like acting on the drive member. A side operated trigger arrangement includes a retention element (22) movably mounted in the housing from a retaining position in which the drive member is kept in a cocked condition and a release position in which the drive member may more forwardly under the influence of the drive spring. An outer sleeve(24)is mounted on the housing movable between a position in which the retention element is prevented from moving to release said plunger and a position in which said retention member is free to move. The outer sleeve includes a trigger wall portion (28) which may be depressed to move the retention element once the retention element (22) is free to move thereby releasing the plunger.
