Drug delivery device

A drug delivery device, including a delivery unit comprising a subcutaneous delivery system including a slidable needle support, an injection needle mounted on the slidable needle support, and an injection needle actuation mechanism configured to engage and slidably move the slidable needle support from a retracted position where the injection needle is within a housing of the drug delivery device to an extended delivery position where the injection needle projects through a skin contact wall of the housing, wherein the needle actuation mechanism comprises a slider-crank linkage mechanism comprising a crank rod pivotally connected to the housing, a connecting rod pivotally connected to the crank rod and pivotally connected to the slidable needle support, and a spring biasing the slider-crank linkage mechanism from a first retracted position prior to use where the needle is fully inserted within the housing towards an extended position for drug administration and further to a second retracted position after drug administration, further comprising a stopper configured to stop the slideable needle support or slider-crank linkage mechanism in the extended position for drug administration, the stopper configured to be displaced to release the slider-crank linkage mechanism after use and removal of the drug delivery device, wherein the stopper forms a skin contact wall portion configured to be in abutment against the skin of the patient during drug administration, wherein the skin contact wall portion comprises a needle orifice formed therethrough configured to allow the injection needle to pass therethrough between the extended and retracted positions.