Injection pen

The claimed invention relates to the field of medical technology, and more particularly to a device for the delivery of a drug in the form of an injection, and which can be used for the self-administration of a selectively metered dose of a drug, predominantly insulin, by a patient. The technical result of the claimed invention is that the pressing force required during the administration of the medication is reduced, the dosing accuracy is increased, and the unobstructed reciprocating movement of the plunger rod is allowed. The technical effect is achieved by an injection pen comprising a housing having an internal thread for engagement with a dosing device provided within the housing and connected to a holder for a cartridge containing a medicament, and further comprising an actuator mechanism comprising a plunger having a rod, the surface of the rod is provided with a thread for interacting with a thread of a sleeve provided in the housing, in which the dosing device is provided with a spring element mount