Improved medication delivery pen

摘要

A medication delivery pen includes a housing having an actuator disposed in the proximal end of the housing for setting and administering a dosage of medication, a medication-containing cartridge assembly having a cartridge with a pierceably sealed distal end, an open proximal end removably attachable to the distal end of the housing, and a piston in sliding, fluid tight engagement within the cartridge. A drive mechanism is coupled between the actuator and the cartridge to exert an axial force on the piston to inject the set dosage of medication. The actuator triggers the drive mechanism to administer the injection of medication held in the cartridge and a processor is coupled to the actuator to determine a value equal to the dosage set by the actuator. The drive mechanism includes a pair of half nuts in rotational engagement with the actuator, a non-rotatable lead screw having a distal end for exerting the axial force on the piston to inject the set dosage of medication, a proximal end, and threads extending between the proximal and distal ends. The nuts open and close radially to selectively engage with the threads of the lead screw for axially advancing along the lead screw upon rotation of the actuator.