On-body injector and method of use

1. An on-body injector for use with a patient with an injection device having an injection port in fluid communication with a delivery tube, the injection port lying on an injection axis, the on-body injector comprising:

a bolus reservoir;

a bolus injection needle in fluid communication with the bolus reservoir, the bolus injection needle having a bolus injection needle tip aligned with the injection port, the bolus injection needle being slideably biased away from the injection port to define a gap between the bolus injection needle tip and the injection port; and

a button operably connected to the bolus injection needle to slide the bolus injection needle along the injection axis;

wherein the button is operable to advance the bolus injection needle tip to close the gap and advance the bolus injection needle tip into the injection port to form an injection flow path from the bolus reservoir, through the bolus injection needle, through the delivery tube, and into the patient;

wherein the button is further operable to advance a plunger through the bolus reservoir to deliver a predetermined bolus volume to the patient through the injection flow path; and

wherein the plunger blocks the injection flow path when the plunger is at a final position in the bolus reservoir when the predetermined bolus volume has been delivered.

2. The on-body injector of claim 1 wherein the predetermined bolus volume is 2 units of insulin.

3. The on-body injector of claim 1 further comprising a pressurized reservoir in fluid communication with the bolus reservoir.

4. The on-body injector of claim 3 wherein the injection device has an introducer port in fluid communication with the delivery tube, the pressurized reservoir being in fluid communication with the delivery tube through a flow restrictor.

5. The on-body injector of claim 4 wherein the flow restrictor is tubing having a length and interior diameter selected to provide a desired pressure drop.

6. The on-body injector of claim 4 wherein the flow restrictor is selected to provide a basal flow rate selected from the group consisting of 20 units of insulin per 24 hours, 30 units of insulin per 24 hours, and 40 units of insulin per 24 hours.

7. The on-body injector of claim 3 further comprising a fill port in fluid communication with the pressurized reservoir.

8. The on-body injector of claim 3 further comprising a housing defining an interior track, wherein the pressurized reservoir is a spring coil operable to at least partially uncoil within the interior track when the pressurized reservoir is at least partially filled with a therapeutic agent.

9. The on-body injector of claim 1 further comprising a spring operable to slideably bias the bolus injection needle away from the injection port.

10. The on-body injector of claim 1 further comprising a lock operable to secure the on-body injector to the injection device.

11. An on-body injector for use with a patient with an injection device having an introducer port in fluid communication with a delivery tube, the on-body injector comprising:

a pressurized reservoir;

a flow restrictor disposed between the pressurized reservoir and the delivery tube, the flow restrictor being tubing having a length and interior diameter selected to provide a desired pressure drop

a fill port in fluid communication with the pressurized reservoir; and

a housing defining an interior track, wherein the pressurized reservoir is a spring coil operable to at least partially uncoil within the interior track when the pressurized reservoir is at least partially filled with a therapeutic agent.

12. The on-body injector of claim 11 wherein the injection device further has an injection port in fluid communication with the delivery tube, the injection port lying on an injection axis, the on-body injector further comprising:

a bolus reservoir in fluid communication with the pressurized reservoir;

a bolus injection needle in fluid communication with the bolus reservoir, the bolus injection needle having a bolus injection needle tip aligned with the injection port, the bolus injection needle being slideably biased away from the injection port to define a gap between the bolus injection needle tip and the injection port; and

a button operably connected to the bolus injection needle to slide the bolus injection needle along the injection axis;

wherein the button is operable to advance the bolus injection needle tip to close the gap and advance the bolus injection needle tip into the injection port to form an injection flow path from the bolus reservoir, through the bolus injection needle, through the delivery tube, and into the patient; and

wherein the button is further operable to advance a plunger through the bolus reservoir to deliver a predetermined bolus volume to the patient through the injection flow path.

13. The on-body injector of claim 12 wherein the plunger blocks the injection flow path when the plunger is at a final position in the bolus reservoir when the predetermined bolus volume has been delivered.

14. The on-body injector of claim 11 further comprising a lock operable to secure the on-body injector to the injection device.

15. A method of use for an on-body injector with an injection device for delivering a predetermined bolus volume to a patient, the method comprising:

deploying the injection device in the patient, the injection device having a delivery tube placed in the patient and an injection port in fluid communication with the delivery tube;

securing the on-body injector to the injection device, the on-body injector having a bolus injection needle aligned with and spaced apart from the injection port;

depressing a button on the on-body injector to advance the bolus injection needle into the injection port

further depressing the button to deliver the predetermined bolus volume from the on-body injector through the bolus injection needle, through the delivery tube, and into the patient; and

releasing the button to retract the bolus injection needle from the injection port.

16. The method of claim 15 wherein the injection device further comprises an introducer port in fluid communication with the delivery tube, and the on-body injector further comprises a pressurized reservoir, the method further comprising delivering a basal injection from the pressurized reservoir through the delivery tube and into the patient.

17. The method of claim 16 wherein the on-body injector further comprises a fill port in fluid communication with the pressurized reservoir, the method further comprising delivering a therapeutic agent thorough the fill port into the pressurized reservoir.