Surgery – Means for introducing or removing material from body for... – Infrared – visible light – ultraviolet – x-ray or electrical...
Reexamination Certificate
1997-11-17
2003-06-24
Bockelman, Mark (Department: 3762)
Surgery
Means for introducing or removing material from body for...
Infrared, visible light, ultraviolet, x-ray or electrical...
C604S020000
Reexamination Certificate
active
06584349
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to iontophoretic devices for delivery of drugs or medicines to patients transdermally, i.e., through the skin, and more particularly relates to an iontophoretic drug delivery device having low-cost electrodes and which are easy to manufacture.
2. Background of the Invention
Iontophoretic drug delivery systems, have, in recent years, become an increasingly important means of administering drugs.
Presently there are two types of transdermal drug delivery systems, i.e., “passive” and “active.” Passive systems deliver drug through the skin of the patient unaided, an example of which would involve the application of a topical anesthetic to provide local pain relief. Active systems, on the other hand, deliver drug through the skin of the patient through the application of an electromotive force (iontophoresis) to drive ionizable substances (medicament) into the skin so that they can be absorbed by adjacent tissues and blood vessels. Such systems offer advantages clearly not achievable by other modes of administration, such as hypodermic injection which has the associated problem of pain, risk of infection and trauma to the patient as well as avoiding introduction of the drug through the gastrointestinal tract which has problems of inactivation of the medicament.
Conventional iontophoretic devices, such as those described in U.S. Pat. No. 4,820,263 (Spevak, et al.), U.S. Pat. No. 4,927,408 (Haak, et al.) and U.S. Pat. No. 5,084,008 (Phipps), the disclosures of which are hereby incorporated by reference, provide for delivery of a drug or medicament transdermally through iontophoresis. Basically, conventional iontophoretic devices consist of a power source connected to two electrodes, an anode and a cathode, which are individually in ionic contact with an electrolyte or drug reservoir which is in contact with the skin to be treated by the iontophoretic device. When the current is turned on, electrical energy is used to assist in the transport of ionic molecules into the body through the skin, via ionic conduction.
Delivering drugs via iontophoresis was recognized long ago, however, due to several disadvantages and limitations the use iontophoretic drug delivery devices have not enjoyed widespread acceptance in the medical field. One reason is because a practical commercially feasible iontophoretic transdermal drug delivery device is still not available. Two major impediments with respect to iontophoretic devices are cost of manufacture and reliability. As previously noted, one problem encountered in the clinical use of transdermal drug delivery devices is that presently available devices have not been particularly economical. Generally, other methods of administration of medicaments have been less expensive and easier to use. Considerations such as cost, reliability and convenience have also impeded the general acceptance of transdermal drug delivery devices. Many iontophoretic systems include expensive electrode systems, such as Ag anode and AgCl cathode, electronic controls and sophisticated designs which are difficult to manufacture cost effectively.
One of the key components of an iontophoretic patch contributing to the high cost of the device is the electrode system. The problem of the high cost of the electrode system is particularly acute for electrodes being used for long duration iontophoresis (hours) and high current density (>50 &mgr;A/cm
2
) applications. Accordingly, there is a need for an electrode system for an iontophoretic drug delivery device which would eliminate the problems and limitations associated with the prior devices discussed above, yet be easy enough to manufacture and also be cost-effective.
It is, therefore, an object of the present invention to provide an electrode system for an iontophoretic device which is inexpensive, easy to manufacture and reliable An electrode system as described herein may include the present inventions as described for the anode electrode, the cathode electrode or both, the anode and the cathode electrodes, of an iontophoretic electrode system.
It is a further object of the present invention to provide an electrode system for an iontophoretic device capable of producing high specific capacity, for example about 1 mA hr/cm
2
or greater.
It is yet a further object of the present invention to provide an electrode system for an iontophoretic device having good stability and a prolonged shelf-life.
It is yet a further object of the present invention to provide an electrode system for an iontophoretic device having the benefits of low voltage requirements thereby either eliminating or reducing demand on a system battery.
It is a further object of the present invention to provide a transdermal drug delivery device which utilizes cost-effective materials to form the electrode systems.
It is yet a further object of the present invention to provide a transdermal drug delivery device which is simple, convenient, and economical to manufacture and use.
SUMMARY OF THE INVENTION
These and other goals and objectives are satisfied, in accordance with the present invention, wherein one embodiment provides for an iontophoretic electrode assembly comprising an anode patch and a cathode patch.
The anode patch of the iontophoretic electrode assembly which includes an electrode compartment and a skin contact compartment which are in electrical (ionic) communication with one another. The electrode compartment includes an electrolyte and a metal electrode in electrical communication with the electrolyte. The present invention provides one embodiment in which the metal electrode further includes at least two electrochemically active dissimilar metals, such that a first metal provides a coating over a second metal. The coating , bonding and layering discussed herein with respect to the formation of the electrodes can be accomplished using methods known to those having ordinary skill in the art of making iontophoretic electrodes.
The two electrochemically active dissimilar metals form the metal electrode of the anode. An electrochemically active metal, is a metal which is capable of undergoing anodic dissolution (oxidation). Such metals include a bulk base metal, or a non-precious metal or metal composite which are good electron conductors but have limited, if any, chemical inertness. Such bulk metal would be coated with a dissimilar metal, namely, a precious metal or other chemically inert metal. The coating of precious metal (chemically inert metal) prevents the chemical reaction between the base metal and the electrolyte when the anode is in storage or otherwise not use. In this manner, shelf-life of the anode may be extended, while also significantly reducing the cost of manufacturing the electrode, since the electrode is mostly made of non-precious, usually low-cost bulk base metal. In a preferred embodiment, the metal electrode is fabricated substantially from copper, nickel, iron, aluminum, zinc or mixtures thereof which is coated with a layer of silver or other precious or chemically inert metal. An anode formed in accordance with the present invention has been found to exhibit good shelf-life stability as well as good voltage characteristics and stability over a prolonged period of usage in iontophoretic drug delivery devices. Furthermore, in satisfying the objects of the invention, the utilization of a base metal, such as copper, as the bulk material significantly reduces the cost of the anode.
Additionally, the anode of the present invention may be in a solid planar form, by way of example and not limitation, foil, laminates, printed ink on polymeric films and the like; or an open mesh form, by way of example and not limitation, woven, nonwoven screen, expanded foil and the like.
Most preferably the anode is fabricated from an expanded copper foil mesh which is treated with a silver coating. The copper foil mesh provides improved performance and reliability as demonstrated in the examples presented herein. Using silver as only a coating significantl
Bock C. Randolph
DeNuzzio John R.
Haynes John L.
Reddy Vilambi
Sage, Jr. Burton H.
Bockelman Mark
Kirkpatrick & Lockhart LLP
Vyteris, Inc.
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