A drug delivery device comprising or adapted to receive a drug-filled cartridge, comprising a piston rod adapted to be rotated by a drive member to thereby move the piston rod distally during expelling, dose setting means allowing a user to simultaneously set a dose amount to be expelled, and a releasable locking mechanism adapted to rotationally lock the drive member relative to the housing during dose setting. The device further comprises release means actuatable between a dose setting mode and an expelling mode, wherein the locking mechanism is released when the release means is actuated from a dose setting mode to an expelling mode.
