Iontophoretic systems, devices, and methods of delivery of active agents to biological interface

1. A transdermal delivery device to passively deliver active agents to a biological interface, comprising:

an active agent reservoir comprising a first active agent of a first polarity;

an outer active agent membrane comprising a second active agent of the first polarity distributed therein, the outer active agent membrane taking the form of an ion-exchange membrane of a second polarity; and

an interfacial layer having a first side adjacent to the outer active agent membrane and a second side configured to contact a biological interface, the interfacial layer comprising a plurality of freely diffusible monovalent co-ions of the first polarity.

2. The transdermal delivery device of claim 1 wherein the interfacial layer comprises a porous membrane material.

3. The transdermal delivery device of claim 2 wherein the interfacial layer takes the form of a gel or an adhesive.

4. The transdermal delivery device of claim 1 wherein the first polarity of the monovalent co-ions of the interfacial layer being opposite to the second polarity of the ion-exchange membrane.

5. The transdermal delivery device of claim 1 wherein the interfacial layer has a thickness of less than about 100 μm.

6. The transdermal delivery device of claim 1 wherein the first and the second active agents are the same.

7. The transdermal delivery device of claim 1 wherein the plurality of monovalent co-ions have lipophilic counter-ions.

8. The transdermal delivery device of claim 1 wherein the monovalent co-ions have a higher affinity than the second active agent has for the outer active agent membrane.

9. The transdermal delivery device of claim 1 wherein the monovalent co-ions are capable of diffusing to the outer active agent membrane and displacing the second active agent distributed therein.