Drug delivery apparatus

1. A drug delivery apparatus for delivering a drug into a bodily fluid in a bodily cavity over a period of time, the apparatus comprising:

a delivery channel, comprising an outlet, for facilitating fluid flow through a lumen thereof to and from the bodily cavity;

a drug dosing actuator for loading a drug into the delivery channel, controlled independently of a second actuator, while producing negligible flow at the outlet; and

the second actuator for driving the drug and a carrier fluid through the delivery channel, out the outlet, and into the bodily cavity.

2. The apparatus of claim 1 , wherein the drug dosing actuator causes drug flow at a substantially similar rate to the rate at which the second actuator causes drug and carrier fluid flow.

3. The apparatus of claim 1 further comprising a sensor for measuring properties of an endogenous fluid that enters the apparatus.

4. The apparatus of claim 1 , wherein the second actuator comprises a reciprocating membrane.

5. The apparatus of claim 1 , wherein the means for loading drug into the delivery channel while producing substantially negligible flow at the outlet comprises a drug supply reservoir for holding the drug and a waste reservoir for receiving the carrier fluid, the drug supply reservoir fluidically coupled with the delivery channel via a drug supply valve and the waste reservoir fluidically coupled with the delivery channel via a waste valve.

6. The apparatus of claim 5 , wherein the means for loading drug into the delivery channel while producing substantially negligible flow at the outlet further comprises a control system for controlling the drug supply valve, the waste valve, and the first actuator so as to deliver the drug to the bodily cavity with a controlled degree of dilution.

7. The apparatus of claim 5 , wherein the drug supply reservoir is a pressurized reservoir.

8. The apparatus of claim 1 , wherein the apparatus is adapted to be integrated with a cochlear prosthesis for electrically stimulating an auditory system.

9. The apparatus of claim 8 , wherein the apparatus is adapted to deliver drugs to the cochlea to treat hearing disorders.

10. The apparatus of claim 8 , wherein the apparatus is adapted to reduce side effects of implant surgery.

11. The apparatus of claim 8 , wherein the apparatus is adapted to improve performance of the prosthesis.

12. The apparatus of claim 1 , wherein the drug dosing actuator for loading drug into the delivery channel while producing substantially negligible flow at the outlet comprises (i) a reservoir in fluid communication with the delivery channel, and (ii) a dosing pump for driving the drug from the reservoir into the delivery channel and for pulling at least a portion of the carrier fluid out from the delivery channel and into the reservoir.

13. The apparatus of claim 12 , wherein the reservoir is formed in a flat sheet of polyimide.

14. The apparatus of claim 12 , wherein the dosing pump is configured to drive the drug in only one direction.

15. The apparatus of claim 12 , wherein the dosing pump is configured to deliver at least 200 nL per stroke.

16. The apparatus of claim 12 , wherein the reservoir comprises a reservoir channel of greater length than a length of the delivery channel.

17. The apparatus of claim 12 , wherein the reservoir channel length is greater than both a width and a height of the reservoir channel.

18. A method for delivering a drug into a bodily fluid in a bodily cavity over a period of time, the method comprising:

loading, using a dosing pump controlled independently of a second actuator, a drug from a drug supply reservoir into a delivery channel while producing negligible flow at an outlet of the delivery channel; and

activating the second actuator to drive the drug and a carrier fluid through the delivery channel, out the outlet, and into the bodily cavity.

19. The method of claim 18 further comprising reversing the second actuator to reverse carrier fluid flow after delivery of the drug through the outlet.

20. The method of claim 18 , wherein the drug supply reservoir is formed in a flat sheet of polyimide.

21. The method of claim 18 , wherein the second actuator comprises a reciprocating membrane.

22. The method of claim 18 , wherein the second actuator is activated so as to deliver a pulsed flow, thereby preventing or reversing occlusion of the delivery channel.

23. The method of claim 18 , wherein loading the drug from the drug supply reservoir into the delivery channel while producing substantially negligible flow at the outlet of the delivery channel comprises:

opening a drug supply valve to allow the drug from the drug supply reservoir to enter the delivery channel;

opening a waste valve to allow at least a portion of the carrier fluid in the delivery channel to enter a waste reservoir;

closing the drug supply valve after a desired amount of the drug has entered the delivery channel; and

closing the waste valve prior to the drug entering the waste reservoir.

24. The method of claim 23 , wherein a volume of the drug entering the delivery channel displaces an equal volume of the carrier fluid in the delivery channel into the waste reservoir, such that flow is not generated at the outlet.

25. The method of claim 18 , wherein the drug supply reservoir comprises a reservoir channel of greater length than a length of the delivery channel.

26. The method of claim 25 , wherein the reservoir channel length is greater than both a width and a height of the reservoir channel.

27. The method of claim 18 wherein loading the drug from the drug supply reservoir into the delivery channel while producing substantially negligible flow at the outlet of the delivery channel comprises:

activating the dosing pump to drive the drug from the drug supply reservoir into the delivery channel and to pull at least a portion of the carrier fluid out from the delivery channel and into the drug supply reservoir; and

deactivating the dosing pump after delivering a predetermined amount of the drug into the delivery channel.

28. The method of claim 27 , wherein a volume of drug driven into the delivery channel is substantially equal to a volume of the carrier fluid pulled into the drug supply reservoir.

29. The method of claim 27 , wherein the dosing pump drives drug in only one direction.

30. The method of claim 27 , wherein the dosing pump delivers at least 200 nL per stroke.

31. The method of claim 27 , wherein the dosing pump is deactivated after a single stroke.