Multiple use disposable injection pen

1. A medication injection pen, comprising:

a housing;

a dose set knob (DSK) comprising an internal key; and

a dose stop member rotationally engaged with said dose set knob,

wherein rotation of said dose set knob to set a medication dose causes relative rotation between said dose stop member and said dose set knob, and when said dose set knob is rotated to a last dose setting position, at least a portion of said dose stop member rotationally abuts said internal key thereby preventing further rotational movement of said dose set knob in a dose setting direction.

2. The medication injection pen according to claim 1 , wherein

said DSK comprises an internal thread engaging an external thread of said dose stop member, and

a distal end of said internal thread is at said internal key.

3. The medication injection pen according to claim 2 , wherein

a proximal end of said internal thread engages at least a portion of said internal thread of said dose stop member.

4. The medication injection pen according to claim 2 , wherein

a distal end of said internal groove terminates at a distance from said internal key.

5. The medication injection pen according to claim 2 , wherein

said internal key is poisoned such that when said dose stop member reaches a maximum dose condition dialable by said DSK, at least a portion of the dose stop member impinges on an end face of said internal key, with said portion of said dose stop member approaching said proximal end face of said internal key on a path dictated by said internal thread of said DSK.

6. The medication injection pen according to claim 1 , further comprising a driver, wherein

said dose stop member moves axially with respect to said driver during the dose setting and the dose correcting, and

said dose stop member rotates with said driver during the dose injection.

7. The medication injection pen according to claim 6 , further comprising a lead screw, and a break tower, wherein

said break tower is rotationally and axially fixed to said housing, and

said lead screw rotates with said driver with respect to said break tower during dose injection.

8. The medication injection pen according to claim 7 , further comprising a setback member disposed between said DSK and said driver, wherein

said dose stop member is disposed on said setback member,

said setback member moves axially with said DSK during the dose setting and the dose correcting,

said setback member rotates with said DSK during the dose injection, and

said driver rotates with said setback member during dose injection.

9. The medication injection pen according to claim 7 , further comprising a break tower core, wherein

said break tower core is rotationally and axially fixed to said break tower, and

said lead screw is axially fixed and rotatable with respect to said break tower core.

10. The medication injection pen according to claim 9 , wherein

said break tower core is snap fit onto said lead screw, and

said break tower core is snap fit into said break tower.

11. The medication injection pen according to claim 10 , wherein

said lead screw comprises a flange received by a groove of said break tower core , and a thickness of said break tower core at said groove next to said flange is increased.

12. The medication injection pen according to claim 11 , wherein

said break tower core comprises a key received by a notch in said break tower to facilitate rotational locking of said break tower core with respect to said break tower, and

said break tower further comprises a protrusion interacting with said flange of said lead screw to facilitate retention of said lead screw with respect to said break tower.