Drug infusion device, cartridge adapter, and drug infusion system

A cartridge adapter comprising:

• a cartridge holder having a space configured to accommodate therein a drug cartridge, the drug cartridge including a cylinder having a tubular internal space extending in a longitudinal direction, a gasket supported in the internal space so as to be movable in the longitudinal direction, and a drug held in the internal space;
• a piston configured to move the gasket in the longitudinal direction in the internal space of the cylinder when the drug cartridge is attached to the cartridge adaptor;
• a piston guide that movably supports the piston and connected to the cartridge holder;
• and
• a piston driving mechanism configured to drive the piston in the longitudinal direction, wherein:
• the piston driving mechanism comprises:
• a male thread located on an outer circumference of the piston;
• and
• a piston gear having an inner surface on which a female thread that meshes with the male thread is disposed and an outer surface on which gear teeth are disposed, a taper is provided on an end surface of each of the gear teeth,
• the cartridge holder includes an opening, and
• the gear teeth are partially exposed from the opening of the cartridge holder to receive a mechanical force from outside the cartridge adapter.