An additive force device (111) is connectible with a drug delivery device (100) to increase the amount of force exerted by a user on the dose setting knob (24) to facilitate injection. The additive force device (111) includes a first spring (121) and a loading barrel (135) connected to the first spring (121) for storing torque therein. A ratchet assembly (129) is connected to the loading barrel (135) and to the first spring (121). The ratchet assembly (129) has a first position in which torque is stored in the first spring (121) and a second position in which torque is released from the first spring (121). An inner barrel (133) is connected to the ratchet assembly and to the drug delivery device (100). The inner barrel (133) transmits the stored torque from the first spring (121) to the drug delivery device (100) to increase an injection force thereof.