A medication injection device (2) includes a housing (4) and a needled syringe (8) supported by the housing. The needle syringe has a plunger (10) and a volume containing medication. The medication injection device further includes an expelling mechanism (6) operably coupled to the plunger. Additionally, the device includes a thermal locking mechanism (20) operably coupled to the expelling mechanism, comprising a material which is solid when the device is refrigerated and transitions to a liquid or gel-like state at a phase-change temperature when the device is taken out of refrigeration and warms up together with the contained drug to a temperature which is suitable for performing an injection. In the solid state, the material keeps the expelling mechanism locked in a disabling condition inhibiting delivery of the medication and in its liquid state creates an enabling condition permitting delivery of the medication.
