Liquid medicine administration device

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

• providing the liquid medicine administration device, which comprises:
• a housing having a hollow cylindrical shape,
• a syringe accommodated in the housing, 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 plunger biased in a distal direction by a biasing member,
• 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, wherein a lumen in the first needle portion is in communication with a lumen in the second needle portion,
• a needle cover located at least partly inside the housing, the needle cover having a hollow cylindrical shape, having a distal end opening, and covering the first needle portion in an initial state, wherein the needle cover is configured to be displaced in the proximal direction relative to the housing by being pressed against the puncture site such that the first needle portion protrudes from the distal end opening, and
• a locking mechanism that inhibits movement of the plunger in the distal direction in the initial state;
• and
• causing the needle cover to move in the proximal direction, upon which the inhibition of movement of the plunger by the locking mechanism is released, the plunger biased by the biasing member pushes the gasket in the distal direction to move the syringe in the distal direction, the second needle portion punctures a distal end of the syringe to communicate with the medicine chamber of the barrel, and the gasket moves in the distal direction relative to the barrel as the second needle portion punctures the distal end of the syringe.