Surgery – Means for introducing or removing material from body for... – Infrared – visible light – ultraviolet – x-ray or electrical...
Reexamination Certificate
1999-06-09
2002-04-23
Bockelman, Mark (Department: 3762)
Surgery
Means for introducing or removing material from body for...
Infrared, visible light, ultraviolet, x-ray or electrical...
C607S149000
Reexamination Certificate
active
06377847
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to iontophoretic systems for delivering medicaments such as therapeutic drugs and medicines to patients transdermally, i.e., through the skin, and more specifically relates to a stable iontophoretic drug delivery device and a reservoir for use in the same. In addition, the present invention relates to a method for making a stable iontophoretic drug delivery device with long shelf life and the reservoir for use in such a device.
BACKGROUND
Transdermal drug delivery systems have, in recent years, become an increasingly important means of administering drugs. Such systems offer advantages clearly not achievable by other modes of administration such as avoiding introduction of the drug through the gastro-intestinal tract or punctures in the skin to name a few.
Presently, there are two types of transdermal drug delivery systems, i.e., “Passive” and “Active.” Passive systems deliver drug through the skin of the user unaided, an example of which would involve the application of a topical anesthetic to provide localized relief, as disclosed in U.S. Pat. No. 3,814,095 (Lubens). Active systems on the other hand deliver drug through the skin of the user, such as a patient, using iontophoresis, which according to Stedman's Medical Dictionary, is defined as “the introduction into the tissues, by means of an electric current, of the ions of a chosen medicament.”
Conventional iontophoretic devices, such as those described in U.S. Pat. Nos. 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, for delivering a drug or medicine transdermally through iontophoresis, basically consist of two electrodes—an anode and a cathode. Usually, electric current is driven from an external supply into the skin at the anode, and back out at the cathode. Accordingly, there has been considerable interest in iontophoresis to perform delivery of drugs for a variety of purposes. Two such examples, involve the use of Novocaine,™ which is usually injected prior to dental work to relieve pain, and Lidocaine, which is usually applied as a topical, local anesthetic.
Such prior devices have prior hereto not been pre-loaded and self adhering, e.g., they have typically utilized an absorbent pad or porous solid sheet that can be filled with drug solution as the drug reservoir. These absorbent pads or porous sheets have three major disadvantages. First, they must be filled with the drug solution after removal from the package since these pads or porous sheets do not hold the drug solution as the solution is subject to removal and leakage under pressure or flexure. In addition, even after the inconvenient addition of the drug solution and after removal from the package, the absorbent pad or porous sheet reservoir remain subject to leakage and smearing of the drug solution due to pressure or flexure upon the skin. Furthermore, absorbent pads or porous solid sheets can not provide the electrical continuity to complete intimate contact since they lack adhesiveness and flexibility with the skin and its contours.
In addition, prior drug reservoirs have included pastes and unformed viscous semi-solid gels such as for example agar that have both solid and liquid characteristics as described, for example, in U.S. Pat. No. 4,383,529 (Webster), the disclosure of which is hereby incorporated by reference.
Powers et al., U.S. Pat. No. 4,886,277, although suggesting that Lidocaine could be incorporated into the reservoir, fails to solve the resulting problem associated with compatibility with adjacent materials such as conductive layers. Accordingly, such a device would fail to provide sufficient stability for extended shelf life, i.e., more than one year.
However, several disadvantages and limitations have been associated with the use of such devices, including handleability and loadability. For example, the semi-solid agar reservoir disclosed in Webster flows under shear or stress. Furthermore, this disclosed reservoir may melt upon exposure to modest elevated temperatures. The agar is unstable, spontaneously releasing aqueous solution.
Thus, there has been a need for an iontophoretic drug delivery device and a reservoir for use in the same, as well as a method for making the reservoir, which would eliminate the problems and limitations associated with the prior devices discussed above, most significant of the problems being associated with stability, handleability, loadability and electrocontinuity of the reservoir, including chemical and thermal stability of the reservoir and the electrode.
SUMMARY
A reservoir electrode assembly of the present invention for an iontophoretic drug delivery device includes an electrode and a hydrophilic reservoir situated in electrically conductive relation to the electrode. The hydrophilic reservoir is formed from a bibulous hydrophilic cross-linked polymeric material having a first surface and a second surface that is adhesively adherent to the electrode. The first surface of the polymeric material is releasably adhesively adherent when applied to an area of a patient's skin. The polymeric material has a cohesive strength forms an adhesive bond with a bond strength between the second surface of the polymeric material to the electrode that is greater than the cohesive strength of the polymeric material. Additionally, an adhesive bond strength of the first surface of the polymeric material to the applied area of the patient is less than the cohesive strength of the polymeric material so that upon removal of the reservoir assembly of the invention from the applied area of the patient, substantially no polymeric material remains on the applied area and the hydrophilic reservoir remains substantially intact and adhesively adherent to the electrode.
The reservoir electrode of the present invention provides solutions for several problems seen with available iontophoretic reservoir electrodes. The reservoir electrode of the invention, by being adherent to the skin of the patient minimizes current pathway concentrations that often result in irritation and burning caused by incomplete contact of the reservoir electrode assembly to the patient's skin. Because the adhesive bond of the electrode to the patient's skin is less than the cohesive strength of the polymeric material used for the reservoir, substantially no residue from the reservoir material is left behind on the patient's skin. Additionally, since the polymeric reservoir material forms an adhesive bond with the electrode, there is intimate and effective electrical contact between the electrical circuit and the polymeric reservoir material. The reservoir electrode assembly of the invention can be physically smaller than most currently available electrode assemblies because the entire polymeric reservoir is hydrophilic and is utilized to contain drugs and electrolytes. Many current electrode assemblies require hydrophobic polymeric materials to achieve an adhesive tack and another hydrophilic material to retain the aqueous drug and electrolyte used for the iontophoretic delivery. When a hydrophobic and a hydrophilic component are used to form a reservoir, as in the currently available materials, some partitioning of the medicament may occur or there may be some binding of the active compound with the hydrophobic material that reduces the availability of the medicament for delivery. These effects are not seen with the hydrophilic reservoir of the invention.
In contrast to the prior devices discussed above, it has been found that a iontophoretic drug delivery device particularly suited for use to deliver at least one medicament, particularly in a high dose efficiency, can be constructed in accordance with the present invention by the incorporation of an aqueous swollen cross linked water soluble polymeric drug delivery reservoir adhesively coupled to the electrode such that the adhesive strength of the electrode material is greater than the cohesive strength
Eliash Bruce Michael
Keusch Preston
Vilambi NRK
Bockelman Mark
Kirkpatrick & Lockhart LLP
Vyteris, Inc.
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