Title:  Iontophoretic drug delivery device having high-efficiency DC-to-DC energy conversion circuit

United States Patent:  6,167,301

Appl. No.:  520521

An iontophoresis system includes a transdermal patch for placement against the skin of a patient and a controller electrically connected to the patch. The patch includes an anode and cathode electrode, and holds an electrolyte and a medication. The controller includes a DC--DC converter circuit which generates an output voltage that is provided to the anode electrode. The controller also includes an adjustable current regulator circuit. The current regulator circuit is coupled to the cathode electrode and is adjustable to provide a desired current flow through the electrodes and the skin of the patient. The DC--DC converter circuit is responsive to the voltage drop across the electrodes and adjusts its output voltage in response to this voltage drop and changes in the impedance of the patient's skin.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved circuit design for an iontophoretic drug delivery device.

It is another object of the present invention to provide a high efficiency DC--DC converter circuit for use in an iontophoresis system.

It is a further object of the present invention to provide a self-regulating DC--DC converter circuit for an iontophoresis system which adjusts to changes in the impedance of the tissue of a patient undergoing iontophoresis.

It is yet a further object of the present invention to provide a DC--DC converter circuit which adjusts its output voltage in response to a desired drug delivery current or to variations in the impedance of a patient undergoing iontophoresis.

It is yet another object of the present invention to provide a DC--DC converter circuit which is at least partially failsafe to prevent undesired current flow to a patient undergoing iontophoresis.

In accordance with one form of the present invention, an iontophoresis system includes an iontophoretic drug delivery device, commonly called a patch, for placement against the skin of a patient, and a controller electrically connected to the patch and having circuitry for controlling current and voltage provided to the patch. More specifically, the patch includes at least a first electrode, which may act as an anode, and at least a second electrode, which may act as a cathode. The patch also includes containers or other structure for holding an electrolyte and a medication. The electrolyte and medication are situated on the patch such that they are in electrical communication with one or the other of the first and second electrodes.

The controller of the iontophoresis system includes a DC--DC converter circuit. The DC--DC converter circuit generates an output voltage which is provided to at least one of the first and second electrodes.

The controller also includes an adjustable current regulator circuit. The current regulator circuit is coupled to the other electrode and is adjustable to provide a desired current flow through the first and second electrodes and the skin of the patient when the patch is placed on the patient's skin.

The DC--DC converter circuit is responsive to the voltage drop across the first and second electrodes. The circuit adjusts its output voltage in response to this voltage drop to provide just the voltage needed across the electrodes and adjustable current regulator for safe and effective drug delivery to the patient without the wasteful consumption of power. The controller circuitry, which includes both the DC--DC converter circuit and the adjustable current regulator circuit, is also particularly responsive to any sudden changes in current or voltage provided to the patch, such as if the patient's skin impedance suddenly changed or the current regulator circuit is adjusted to provide a different drug delivery current to the patient during the iontophoretic process.

Claim 1 of 1 Claim

What is claimed is:

1. An iontophoresis system control circuit for use with an iontophoretic drug delivery device, the iontophoretic drug delivery device being placeable against the skin of a patient and having at least first and second electrodes, the control circuit comprising:

a series pass regulator circuit, the series pass regulator circuit being responsive to a control voltage and controlling a desired drug delivery current in response thereto, the desired drug delivery current being flowable through the at least first and second electrodes and the skin of the patient, the series pass regulator circuit having a voltage Vs thereacross, the series pass regulator circuit being electrically coupled to the at least second electrode of the iontophoretic drug delivery device;

a step-up DC--DC converter circuit, the step-up DC--DC converter circuit being electrically coupled to the at least first electrode and generating an output voltage V2 which is provided thereto, the impedance of at least one of the iontophoretic drug delivery device and the patient's skin and the desired drug delivery current flowing therethrough resulting in a voltage drop Vp across the at least first and second electrodes, wherein the voltage V2 is equal to the sum of the voltage Vp and the voltage Vs, the DC--DC converter circuit being responsive to the voltage Vp across the at least first and second electrodes and adjusting the output voltage V2 in response thereto so that the voltage Vs across the series pass regulator is substantially equal to the minimum voltage required to allow the series pass regulator to control the desired drug delivery current through the at least first and second electrodes and the patient's skin;

wherein the step-up DC--DC converter circuit includes:

a step-up switching regulator circuit, the step-up switching regulator circuit generating an output signal;

a first switching transistor, the first switching transistor being responsive to the output signal of the step-up switching regulator circuit and switching between a conducting and non-conducting state in response thereto;

an inductor, the inductor being responsive to the state of the first switching transistor and storing energy in response thereto, the inductor having a tap and generating an output signal on the tap; and

a second transistor, the second transistor being coupled to the tap of the inductor and being responsive to the output signal on the tap of the inductor, and switching between a conducting and non- conducting state in response thereto, the second transistor providing at least in part the output voltage V2.

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.