Transdermal delivery device

1. A transdermal delivery device comprising:

a canister that includes an elongated spout through which a substance is dispensable from the canister;

a housing in which the canister is configured to be installed and replaced, the housing including a dispensing mechanism that is operable to dispense the substance from the canister through the spout when the canister is installed in the housing; and

a plate of the housing having an external surface that is placeable against skin, the external surface including a plurality of channels that radiate from an opening in the plate, the spout, when the canister is installed in the housing, being configured to extend outward through the opening to the external surface of the plate so as to dispense the substance directly from the canister onto the skin without an intervening conduit, the channels configured to distribute the substance over the plate, the plate including at least one iontophoresis electrode that is chargeable to generate an electric field to enable transdermal delivery of an active ingredient of the substance when the substance is dispensed onto the skin by the spout when the external surface of the plate is placed on the skin.

2. The device of claim 1 , wherein the dispensing mechanism comprises an electric motor.

3. The device of claim 1 , wherein the dispensing mechanism comprises a worm and a nut.

4. The device of claim 1 , wherein the dispensing mechanism is configured to push a piston into the canister.

5. The device of claim 1 , wherein the plurality of channels is electrically isolated from said at least one iontophoresis electrode.

6. The device of claim 1 , wherein the dispensing mechanism is controllable to dispense a predetermined quantity of the substance.

7. The device of claim 1 , wherein a charge that is applied to said at least one iontophoresis electrode is adjustable.

8. The device of claim 1 , comprising a return electrode that is configured such that when said at least one iontophoresis electrode and the return electrode are placed in contact with separate regions of the skin, the skin completes an electrical circuit between the iontophoresis electrode and the return electrode.

9. The device of claim 8 , wherein the return electrode is placed on an outer surface of the device such that when the device is held in a hand, the hand contacts the return electrode.

10. The device of claim 1 , wherein a surface of said at least one iontophoresis electrode is roughened.

11. A method for transdermal delivery of an active ingredient of a substance, the method comprising:

installing a replaceable canister in a housing of a transdermal delivery device such that a spout of the canister extends outward through an opening in a plate of the housing to an external surface of the plate;

operating a dispensing mechanism of the housing so as to dispense the substance from the canister directly, without an intervening conduit, onto a region of skin via the spout and the opening to the external surface and via a plurality of channels on the external surface that radiate outward from the opening, the substance comprising an active ingredient with ionized molecules; and

operating an iontophoresis electrode on the external surface of the plate when the iontophoresis electrode is in contact with the region of the skin to electrically charge the iontophoresis electrode with a charge whose sign is identical to a sign of a charge of the ionized molecules.

12. The method of claim 11 , wherein operating the dispensing mechanism comprises operating the dispensing mechanism to dispense a predetermined quantity of the substance.

13. The method of claim 12 , wherein the predetermined quantity is determined in accordance with a sensed characteristic of the skin.

14. The method of claim 13 , wherein the characteristic is selected from a group of characteristics consisting of temperature, moistness, impedance, and conductance.

15. The method of claim 11 , further comprising placing a return electrode of the device in contact with a region of the skin that is separated from the region of the skin where the iontophoresis electrode is placed.

16. The method of claim 15 , comprising measuring an electrical current between the iontophoresis electrode and the return electrode.