Liquid medicine administration device

A method of operating a liquid medicine administration device, the method comprising:

• providing the liquid administration device, which comprises:
• a housing having a hollow cylindrical shape;
• a syringe unit accommodated in the housing so as to be movable in a distal direction along an axial direction of the housing, the syringe unit comprising a syringe, the syringe comprising:
• a barrel having a medicine chamber filled with a liquid medicine, and
• a gasket slidable inside the barrel in a liquid-tight manner;
• a double-ended needle disposed inside the housing and comprising a first needle portion that protrudes in the distal direction for puncturing a puncture site, and a second needle portion that protrudes in a proximal direction toward the syringe;
• and
• a guide mechanism that is interposed between the housing and the syringe unit and that guides the syringe unit in the distal direction, wherein the guide mechanism comprises:
• a guide rib extending in the axial direction, and
• a guide groove that extends in the axial direction and engages with the guide rib;
• and
• causing the syringe unit to be pushed by a plunger, such that the syringe unit moves in a distal direction along the housing and the guide rib moves in the distal direction along the guide groove, and the syringe unit is guided in the distal direction.