Iontophoretic Delivery Device and Method of Hydrating Same

This invention relates to a device for delivering an agent transdermally or transmucosally by iontophoresis. More particularly, this invention relates to an electrically powered iontophoretic delivery device having a liquid reservoir which is initially isolated from other initially dry components of the device. The liquid in the liquid reservoir is used to hydrate the dry components, allowing the device to be activated just before use.

Iontophoresis, according to Dorland's Illustrated Medical Dictionary, is defined to be "the introduction, by means of electric current, of ions of soluble salts into the tissues of the body for therapeutic purposes." Iontophoretic devices have been known since the early 1900's. British patent specification No. 410,009 (1934) describes an iontophoretic device which overcame one of the disadvantages of such early devices known to the art at that time, namely the requirement of a special low tension (low voltage) source of current which meant that the patient needed to be immobilized near such source. The device of that British specification was made by forming a galvanic cell from the electrodes and the material containing the medicament or drug to be delivered transdermally. The galvanic cell produced the current necessary for iontophoretically delivering the medicament. This ambulatory device thus permitted iontophoretic drug delivery with substantially less interference with the patient's daily activities.

More recently, a number of United States patents have issued in the iontophoresis field, indicating a renewed interest in this mode of drug delivery. For example, U.S. Pat. No. 3,991,755 issued to Vernon et al; U.S. Pat. No. 4,141,359 issued to Jacobsen et al; U.S. Pat. No. 4,398,545 issued to Wilson; and U.S. Pat. No. 4,250,878 issued to Jacobsen disclose examples of iontophoretic devices and some applications thereof. The iontophoresis process has been found to be useful in the transdermal administration of medicaments or drugs including lidocaine hydrochloride, hydrocortisone, fluoride, penicillin, dexamethasone sodium phosphate, insulin and many other drugs. Perhaps the most common use of iontophoresis is in diagnosing cystic fibrosis by delivering pilocarpine salts iontophoretically. The pilocarpine stimulates sweat production; the sweat is collected and analyzed for its chloride content to detect the presence of the disease.

In presently known iontophoretic devices, at least two electrodes are used. Both of these electrodes are disposed so as to be in intimate electrical contact with some portion of the skin of the body. One electrode, called the active or donor electrode, is the electrode from which the ionic substance, medicament, drug precursor or drug is delivered into the body by iontophoresis. The other electrode, called the counter or return electrode, serves to close the electrical circuit through the body. In conjunction with the patient's skin contacted by the electrodes, the circuit is completed by connection of the electrodes to a source of electrical energy, e.g., a battery. For example, if the ionic substance to be delivered into the body is positively charged (i.e., a cation), then the anode will be the active electrode and the cathode will serve to complete the circuit. If the ionic substance to be delivered is negatively charged (i.e., an anion), then the cathode will be the active electrode and the anode will be the counter electrode.

Alternatively, both the anode and cathode may be used to deliver drugs of opposite charge into the body. In such a case, both electrodes are considered to be active or donor electrodes. For example, the anode can deliver a positively charged ionic substance into the body while the cathode can deliver a negatively charged ionic substance into the body.

It is also known that iontophoretic delivery devices can be used to deliver an uncharged drug or agent into the body. This is accomplished by a process called electroosmosis. Transdermal delivery of neutral compounds by the phenomenon of electroosmosis is described by Hermann Rein in Zeitschrift fur Biologie, Bd. 81, pp 125-140 (1924) and the transdermal delivery of nonionic polypeptides by the phenomenon of electroosmosis is described in Sibalis et al. U.S. Pat. Nos. 4,878,892 and 4,940,456. Electroosmosis is the transdermal flux of a liquid solvent (e.g., the liquid solvent containing the uncharged drug or agent) which is induced by the presence of an electric field imposed across the skin by the donor electrode. As used herein, the terms "iontophoresis" and "iontophoretic" encompass both the delivery of charged ions as well as the delivery of uncharged molecules by the associated phenomenon of electroosmosis.

Iontophoretic delivery devices generally require a reservoir or source of the beneficial agent (which is preferably an ionized or ionizable agent or a precursor of such agent) to be iontophoretically delivered or introduced into the body. Examples of such reservoirs or sources of ionized or ionizable agents include a pouch or cavity as described in the previously mentioned Jacobsen U.S. Pat. No. 4,250,878, a porous sponge or pad as disclosed in Jacobsen et al. U.S. Pat. No. 4,141,359, or a pre-formed gel body as described in Webster U.S. Pat. No. 4,383,529 and Ariura et al. U.S. Pat. No. 4,474,570. Such drug reservoirs are electrically connected to the anode or the cathode of an iontophoresis device to provide a fixed or renewable source of one or more desired agents.

Iontophoretic delivery devices which are attachable at a skin surface and rely on electrolyte fluids to establish electrical contact with such skin surfaces can be divided into at least two categories. The first category includes those devices which are prepackaged with the liquid electrolyte contained in the electrode receptacle. The second type of device uses dry-state electrodes whose receptacles are customarily filled with liquid drug/electrolyte immediately prior to application to the body. With both types of devices, the user currently experiences numerous problems which make their use both inconvenient and problematic.

With respect to the prefilled device, storage is a major concern. Many drugs have poor stability when in solution. Accordingly, the shelf life of prefilled iontophoretic drug delivery devices is unacceptably short. Corrosion of the electrodes and other electrical components is also a potential problem with prefilled devices. For example, the return electrode assembly will usually contain an electrolyte salt such as sodium chloride which over time can cause corrosion of metallic and other electrically conductive materials in the electrode assembly. Leakage is another serious problem with prefilled iontophoretic drug delivery devices. Leakage of drug or electrolyte from the electrode receptacle can result in an inoperative or defective state. Furthermore, such prefilled devices are difficult to apply because the protective seal which covers the electrode opening and retains the fluid within the receptacle cavity must be removed prior to application on the skin. After removal of this protective seal, spillage often occurs in attempting to place the electrode on the skin. Such spillage impairs the desired adhesive contact of the electrode to the skin and also voids a portion of the receptacle cavity. The consequent loss of drug or electrolyte fluid tends to disrupt electrical contact with the electrode plate contained therein and otherwise disrupts the preferred uniform potential gradient to be applied.

Although dry-state electrodes have numerous advantages in ease of storage, several problems remain. For example, the drug and electrolyte receptacles of such a device are conventionally filled through an opening prior to application of the device to the patient's skin. Therefore, the same problem of spillage and loss of drug or electrolyte upon application occurs as with the prefilled electrode.

Frequently, such electrodes are not well structured to develop the proper uniform current flow required in iontophoresis applications. Such nonuniform current flow may result from the occurrence of air pockets within the receptacle cavity at the skin surface. Such effects are particularly troublesome in iontophoresis applications, where a nonuniform current distribution may result in excessive skin irritation or "burning"

More recently, iontophoretic delivery devices have been developed in which the donor and counter electrode assemblies have a "multilaminate" construction. In these devices, the donor and counter electrode assemblies are each formed of multiple layers of (usually) polymeric matrices. For example, Parsi U.S. Pat. No. 4,731,049 discloses a donor electrode assembly having hydrophilic polymer based electrolyte reservoir and drug reservoir layers, a skin-contacting hydrogel layer, and optionally one or more semipermeable membrane layers. In addition, Ariura et al, U.S. Pat. No. 4,474,570 discloses a device wherein the electrode assemblies include a conductive resin film electrode layer, a hydrophilic gel reservoir layer, an aluminum foil conductor layer and an insulating backing layer.

The drug and electrolyte reservoir layers of iontophoretic delivery devices have typically been formed of hydrophilic polymers. See for example, Ariura et al, U.S. Pat. 4,474,570; Webster U.S. Pat. No. 4,383,529 and Sasaki U.S. Pat. No. 4,764,164. There are several reasons for using hydrophilic polymers. First, water is a biocompatible, highly polar solvent and therefore preferred for ionizing many drug salts. Secondly, hydrophilic polymer components (i.e., the drug reservoir in the donor electrode and the electrolyte reservoir in the counter electrode) can be hydrated while attached to the body by absorbing water from the skin or from a mucosal membrane. For example, skin contacting electrodes can be hydrated by absorbing sweat or water from transepidermal water loss. Similarly, electrodes attached to an oral mucosal membrane can be hydrated by absorbing saliva. Once the drug and electrolyte reservoirs become hydrated, ions are able to move through the reservoirs and across the tissue, enabling the device to deliver agent to the body. Hydrogels have been particularly favored for use as the drug reservoir matrix and electrolyte reservoir matrix in iontophoretic delivery devices, in part due to their high equilibrium water content and their ability to absorb water from the body. In addition, hydrogels tend to have good biocompatibility with the skin and with mucosal membranes. However, since many drugs and certain electrode components are unstable in the presence of water, iontophoretic drug delivery devices having a drug reservoir formed of a prehydrated hydrogel may also have an unacceptably short shelf life. One solution to the drug stability problem is to use hydrophilic polymer drug and electrolyte reservoirs which are in a substantially dry state, i.e. in a non-hydrated condition. The drug and/or electrolyte can be dry blended with the hydrophilic polymer and then cast or extruded to form a non-hydrated, though hydratable, drug or electrolyte containing reservoir. Unfortunately, the non-hydrated hydrophilic polymer components must first absorb sufficient quantities of water from the body before the device can operate to deliver drug. This delivery start-up period can take in excess of 8 hours. This delay makes many devices unsuited for their intended purpose. For example, when using an iontophoretic delivery device to apply a local anesthetic in preparation for a minor surgery (e.g., surgical removal of a mole), the surgeon and the patient must wait until the drug and electrolyte reservoirs of the delivery device become sufficiently hydrated before the anesthetic is delivered in sufficient quantities to induce anesthesia. Similar delays are encountered with other drugs.

In response to these difficulties, Konno et al. in U.S. Pat. No. 4,842,577 disclose in FIG. 4 an iontophoretic electrode assembly having a substantially non-hydrated drug containing matrix and a separate water reservoir which is initially sealed, using a foil sheet, from the drug containing portions of the electrode. Unfortunately, this electrode design is not only difficult to manufacture but also is subject to severe handling restrictions. In particular, there is a tendency for the foil seal to be inadvertently broken during manufacture, packaging and handling of the electrode. This can have particularly drastic consequences especially when the seal is broken during manufacture of the device. Once the seal is broken, water is wicked into the drug-containing reservoir which can cause degradation of the drug and/or other components before the device is ever used.

Another disadvantage of using non-hydrated hydrophilic polymer components is that they have a tendency to delaminate from other parts of the electrode assembly during hydration. For example, when utilizing a drug reservoir matrix or an electrolyte reservoir matrix composed of a hydrophilic polymer, the matrix begins to swell as it absorbs water from the skin. In the case of hydrogels, the swelling is quite pronounced. Typically, the drug or electrolyte reservoir is in either direct contact, or contact through a thin layer of an ionically conductive adhesive, with an electrode. Typically, the electrode is composed of metal (e.g., a metal foil or a thin layer of metal deposited on a backing layer) or a hydrophobic polymer containing a conductive filler (e.g., a hydrophobic polymer loaded with carbon fibers and/or metal particles). Unlike the hydrophilic drug and electrolyte reservoirs, the electrodes do not absorb water and do not swell. The different swelling properties of the hydrophilic reservoirs and the electrodes results in shearing along their contact surfaces. In severe cases, the shearing can result in the complete loss of electrical contact between the electrode and the drug/electrolyte reservoir resulting in an inoperable device.

Thus, it is an object of the present invention to provide an iontophoretic drug delivery device with agent-containing electrode components which are manufactured in an initially non-hydrated or dry state but which can be quickly hydrated prior to placement on the body.

It is another object of this invention to provide an improved method of quickly hydrating the electrodes in an iontophoretic delivery device in order to minimize the "start-up" delay of an iontophoretic delivery device.

It is a further object of this invention to provide an iontophoretic drug delivery device which cannot be inadvertently hydrated prior to actual use.

It is a still further object of this invention to provide a method of hydrating the hydrophilic components of a dry state multilaminate iontophoresis electrode assembly without the delamination problems encountered with the prior art electrodes.

These and other objects are met by an electrically powered iontophoretic agent delivery device and a method of hydrating same. In accordance with one embodiment of the invention, the delivery device includes at least one multilaminate dry state electrode assembly and a source of electrical power which is electrically connected to the electrode assembly. The electrode assembly includes a reservoir layer comprised of a substantially non-hydrated hydratable matrix adapted to contain an agent to be delivered. The electrode assembly is adapted to be placed in agent transmitting relation with a body surface, such as intact skin or a mucosal membrane, for delivery of agent therethrough. The electrode assembly also includes an electrode layer in electrical contact with both the power source and the reservoir layer.

The electrode assembly has a means for hydrating the substantially non-hydrated matrix. Said means for hydrating the matrix includes a preformed passageway through the electrode layer. The passageway establishes fluid communication between the exterior of the device and the non-hydrated matrix. The electrode assembly is activated by introducing a liquid from an external source through the preformed passageway through the electrode layer into the hydratable reservoir layer.

Preferably, the liquid comprises water. In the case of a donor electrode assembly, the agent preferably comprises a drug. In the counter electrode assembly, the agent preferably comprises an electrolyte salt. Most preferably, both the agent and the electrolyte salt are soluble in the liquid. The agent and/or the electrolyte salt may be present in the non-hydrated matrix either before hydration or maybe added to the non-hydrated matrix with the liquid at the time of hydration. When the non-hydrated matrix already contains the agent, the liquid preferably comprises deionized water. When the non-hydrated matrix initially contains no agent, the liquid preferably comprises an aqueous solution or suspension of a drug or an electrolyte salt. Most preferably, the matrix of the reservoir layer is comprised of a hydrophilic polymer.

In accordance with a second embodiment of the invention, a multilaminate dry state electrode assembly for an electrically powered iontophoretic agent delivery device, and a method of hydrating the electrode assembly, are provided. The electrode assembly is adapted to be placed in agent transmitting relation with a body surface such as intact skin or a mucosal membrane, for delivery of agent therethrough. The electrode assembly includes an electrode layer in electrical contact with an electrical power source and adapted to be placed in electrical contact with a reservoir layer. The reservoir layer is adapted to contain an agent to be delivered. The reservoir layer comprises a substantially non-hydrated, hydratable matrix which is initially separated from the electrode layer and the power source. The reservoir layer has an exposable surface for introducing a liquid thereto in order to hydrate the reservoir layer. After hydration, the reservoir layer is placed in electrical contact with the electrode layer.

Also provided is a method for hydrating the device. The method includes separating the reservoir layer from the electrode layer while the reservoir layer is in a substantially non-hydrated condition. A hydrating liquid is introduced into the reservoir layer in an amount sufficient to permit ion transport through the reservoir layer. Thereafter, the hydrated reservoir layer is secured in electrical contact with the electrode layer.

Preferably, the hydrating liquid comprises water. In the case of a donor electrode assembly, the agent preferably comprises a drug. In the counter electrode assembly, the agent preferably comprises an electrolyte salt. Most preferably, both the agent and the electrolyte salt are soluble in the liquid. The agent and/or the electrolyte salt may be present in the non-hydrated matrix either before hydration or may be added to the non-hydrated matrix with the liquid at the time of hydration. When the non-hydrated matrix already contains the agent, the liquid preferably comprises deionized water. When the non-hydrated matrix initially contains no agent, the liquid preferably comprises an aqueous solution or suspension of a drug or an electrolyte salt. Most preferably, the matrix of the reservoir layer is a hydrophilic polymer. This embodiment of the invention has particular utility where the hydrophilic polymer has a tendency to swell upon hydration. Most preferably, the hydrated reservoir layer is secured in electrical contact with the electrode layer after the swelling of the reservoir layer is substantially complete.

FIG. 1 is a schematic top view of an iontophoretic drug delivery device according to the present invention;

FIG. 2 is a schematic end view of the device shown in FIG. 1;

FIG. 3 is a schematic end view of another iontophoretic delivery device according to the present invention;

FIG. 4 is a schematic top view of a portion of another iontophoretic delivery device according to the present invention.

FIG. 5 is a schematic side view of the device shown in FIG. 4, during assembly;

FIG. 6 is a schematic side view of another iontophoretic delivery device according to the present invention;

FIG. 7 is a schematic side view of another iontophoretic delivery device according to the present invention;

FIG. 8 is a schematic side view of another iontophoretic delivery device according to the present invention; and

FIG. 9 is a schematic side view of another iontophoretic delivery device according to the present invention.

In the figures, like elements are designated by the same reference number in the several drawings.

FIG. 6 is a schematic view of an iontophoretic delivery device 10 for delivering a beneficial agent through a body surface such as intact skin or a mucosal membrane. Iontophoretic delivery device 10 includes a donor electrode assembly 8 and a counter electrode assembly 9. The donor electrode assembly 8 and the counter electrode assembly 9 are physically attached to insulator 26 and form a single self-contained unit. Insulator 26 prevents the electrode assemblies 8 and 9 from short circuiting the device by preventing direct electrical and/or ion transport between the electrode assemblies 8 and 9. Electrode assemblies 8 and 9 are connected in series, by appropriate electrical conductors, with an electrical power source. The power source and the electrical conductors are schematically shown as layer 14. The power source used to power device 10 is typically one or more low voltage batteries. A water impermeable backing layer 13 preferably covers layer 14 with its associated electrical components.

The donor electrode assembly 8 includes an electrode layer 11 and a reservoir layer 15. The reservoir 15 contains the beneficial agent to be iontophoretically delivered by device 10. A rate controlling membrane layer 19 is optionally positioned between the reservoir layer 15 and the body surface for controlling the rate at which the agent is delivered to the body surface or for preventing the delivery of agent to the body surface when the device is turned off. Counter electrode assembly 9 contacts the body surface at a location spaced apart from electrode assembly 8. Counter electrode assembly 9 includes an electrode layer 12 and a reservoir layer 16. Device 10 can be adhered to the body surface by means of ion-conducting adhesive layers 17 and 18. As an alternative to the ion-conducting adhesive layers 17 and 18 shown in FIG. 6, device 10 may be adhered to the body surface using an adhesive overlay. Any of the conventional adhesive overlays used to secure passive transdermal delivery devices to the skin may be used.

When the device 10 is in storage, no current flows because the device does not form a closed circuit. When the device 10 is placed on the skin or mucosal membrane of a patient and the electrode assemblies 8 and 9 are sufficiently hydrated to allow ions to flow through the various layers of electrode assemblies 8 and 9, the circuit between the electrodes is closed and the power source begins to deliver current through the device and through the body of the patient. The donor and counter electrode assemblies 8 and 9 normally include a strippable release liner, not shown, which is removed prior to application of electrode assemblies 8 and 9 to a body surface.

As shown in FIG. 6, the donor electrode assembly 8 includes a flexible pouch 21 containing a plurality of liquid-containing capsules. Pouch 21 is preferably formed of a liquid-permeable material such as fabric or netting made from natural and/or synthetic materials. Alternatively, pouch 21 may be formed of a liquid-impermeable sheet material, with the bottom tip of pouch 21 either open or sealed with a rupturable seal which is broken upon depressing the top of pouch 21, to provide a fluid flow path to wicking layer 23.

Methods of encapsulating aqueous liquids are described for example in U.S. Pat. Nos. 3,423,489 and 3,674,704, the disclosures of which are incorporated herein by reference. As a specific example, the liquid-containing capsules may be spherical, having a diameter of up to about 4 mm. The capsule walls are preferably formed of metable and non-water soluble coatings such as fats, waxes and thermoplastic polymers. The capsules typically have a relatively uniform wall thickness of about 0.001 mm to 0.5 mm. Additional liquid-containing capsules and methods of making same are described in the Kirk-Othmer Encyclopedia of Chemical Technology, 3rd, Ed., Vol. 15, pps 470-493; and "A New Method of Preparing Monocured Water-loaded Microcapsules Using Interfacial Polymer Deposition Process", Uno et al., Journal of Microencapsulation, (1984) Vol. 1, No. 1, pps 3-8.

The rounded top portion of pouch 21 is flexible allowing the user to depress the pouch in order compress the contents of the pouch thereby fracturing the capsule walls and releasing the water into wicking-layer 23. When pouch 21 is formed of a liquid-permeable material such as a fabric or netting, the water released from the fractured capsules freely flows into wicking layer 23 and/or reservoir layer 15. When pouch 21 is formed of a liquid impermeable material, such as a polyethylene sheet material, the bottom tip of pouch 21 must be left open or alternatively must be formed of a rupturable seal which is ruptured upon depressing the top portion of pouch 21. Water from the fractured capsules is thereby free to flow through the open tip of pouch 21 into layer 23 and/or 15.

Pouch 21 containing water-containing capsules may be manufactured using known techniques. Typically, pouch 21 is manufactured using conventional form, fill and seal techniques wherein the pouch 21 is first formed, then filled with the water-containing capsules and then appropriately sealed. The assembled pouch 21 is then simply inserted into device 10.

Pouch 21 extends through the electronic component layer 14, the donor electrode layer 11 but preferably not through the impermeable backing layer 13. The donor electrode assembly 8 optionally includes a layer 23 of a liquid-wicking material. Any liquid introduced through the tip of pouch 21 is quickly wicked by layer 23 across the entire top surface of agent reservoir 15. The pouch 21, optionally with the wicking layer 23, enables a liquid to be introduced directly into the matrix of reservoir layer 15 in order to hydrate the matrix, and optionally to hydrate the layers 23, 19 and/or 17 if they are present, and to activate the donor electrode assembly 8 immediately before use. In most cases the liquid used to hydrate the matrix of reservoir 15 will be water, but other liquids including non-aqueous liquids, can also be used to "hydrate" (i.e., activate) the matrix of reservoir layer 15. In the typical case where the liquid is water, the matrix of reservoir layer 15 will be at least partly composed of a hydrophilic material such as a hydrophilic polymer, a cellulosic sponge or pad, or other water retaining material. Most preferably, the matrix of reservoir layer 15 will be at least partly composed of a hydrophilic polymer of the type described hereinafter.

As an alternative to the wicking layer 23, the top surface of reservoir layer 15 may be provided with a plurality of grooves (not shown) in fluid communication with the tip of pouch 21. The grooves distribute any liquid introduced from pouch 21 across the upper surface of reservoir layer 15.

Similarly, a pouch 22 containing a plurality of liquid-containing capsules is provided in the counter electrode assembly 9. Pouch 22 is formed of the same materials and using the same techniques as described above in connection with pouch 21. As shown, pouch 22 extends through the electrode layer 12 and the electronic component layer 14. An optional liquid wicking layer 24 may be provided between reservoir layer 16 and electrode layer 12 in counter electrode assembly 9. Wicking layer 24 has a similar function to wicking layer 23 in the donor electrode assembly 8. The pouch 22, optionally with the wicking layer 24, enables the encapsulated liquid to be released from the capsules by depressing the top of pouch 22 and introduced through the open or rupturable tip of pouch 22 directly into the matrix of reservoir layer 16 in order to hydrate the matrix, and optionally to hydrate the layers 24 and/or 18 if there are present, and to activate the counter electrode assembly 9. As with the donor electrode assembly 8, the liquid used to hydrate the matrix of reservoir layer 16 will typically be water, although other liquids including non-aqueous liquids, can also be used. As an alternative to layer 24, the top surface of reservoir layer 16 may also be provided with a plurality of grooves which can distribute any liquid introduced from pouch 22 across the upper surface of reservoir layer 16.

Backing layer 13 formed of a liquid impermeable material prevents liquid from the exterior environment from entering the device and enables device 10 to be worn on the body without danger of admitting liquids, such as ordinary tap water from bathing, containing extraneous ions or other contaminants into the reservoir layers 15 and 16.

In accordance with the present invention, at least one of electrode assemblies 8 and 9, and preferably both electrode assemblies 8 and 9 are initially in a substantially dry state. Thus, the various ion transporting layers making up electrode assemblies 8 and 9 are initially in a non-hydrated condition. As used herein, the terms "dry state" and "non-hydrated" mean that the particular layer contains an insufficient amount of liquid to permit ion transport therethrough. For example, the ion transmitting layers of donor electrode assembly 8 include reservoir layer 15 and optional layers 17, 19 and 23. In order for donor electrode assembly 8 to be considered a "dry state" electrode, none of layers 15, 17, 19 and 23 are sufficiently hydrated to allow ion transport therethrough.

Similarly, in order for counter electrode assembly 9 to be considered a "dry state" electrode, none of reservoir layer 16 or optional layers 18 and 24 contains sufficient liquid to allow ion transport therethrough.

In order to be considered "non-hydrated" reservoir layers 15 and 16 should generally contain less than about 10 wt. % liquid, preferably less than about 5 wt. % liquid and most preferably less than about 1 wt. % liquid.

In order to activate delivery device 10, reservoir layers 15 and 16, as well as the optional adhesive layers 17 and 18 and membrane layer 19, must become sufficiently hydrated to enable agent to be transported therethrough by iontophoresis. In order to hydrate reservoir layers 15 and 16, as well as the optional adhesive layers 17 and 18 and membrane layer 19, an encapsulated liquid (typically water) is released from the capsules in pouches 21 and 22.

In most cases, the liquid introduced into device 10 from pouches 21 and 22 will be composed at least in part of water. However, it is well within the scope of the present invention to "hydrate" the reservoir layers 15 and 16 using other liquids including non-aqueous liquids such as alcohols and glycols. Accordingly, as used herein, the term "hydrate" refers to the addition of either aqueous or non-aqueous based liquids from pouches 21 and 22. Furthermore, in those instances where the non-hydrated reservoir layers 15 and/or 16 initially contain no drug or electrolyte, the encapsulated hydrating liquid may comprise a liquid solution or suspension of the drug or electrolyte.

FIGS. 7 and 8 illustrate two alternative iontophoretic delivery devices 70 and 80, respectively. In device 70, the encapsulated liquid-containing pouches 21 and 22 are positioned at either end of the device. Thus, pouch 21 is positioned adjacent reservoir layer 15, optionally with a wicking layer 23 positioned between pouch 21 and reservoir layer 15. Similarly, pouch 22 is positioned adjacent reservoir layer 16, optionally with a wicking layer 24 positioned therebetween. Device 70 is activated by squeezing pouches 21 and 22, which causes the capsules therein to break and release liquid. The liquid is thereby introduced either directly into reservoir layers 15 and 16, or indirectly through the wicking layers 23 and 24, respectively. Optionally, pouches 21 and 22 can be removed from device 70 after releasing liquid into reservoir layers 15 and 16, respectively.

FIG. 8 discloses a similar device 80 wherein the pouches 21 and 22 are positioned on the inner sides of reservoir layers 15 and 16, respectively. Like the device illustrated in FIG. 7, device 80 is also activated by squeezing pouches 21 and 22 causing the capsules to break and release liquid into reservoir layers 15 and 16, optionally through wicking-layers 23 and 24, respectively. As with device 70, pouches 21 and 22 may optionally be removed after releasing liquid into reservoir layers 15 and 16.

FIG. 9 discloses a similar device 90 wherein the encapsulated liquid-containing pouches 21 and 22 are positioned at either end of the device, as in FIG. 7. The bottom surfaces of pouches 21 and 22 are each coated with an adhesive layer 17 and 18, respectively. In this configuration, the pouches 21 and 22 serve both as a means to hydrate reservoir layers 15 and 16, respectively, as well as a peripheral adhesive to secure device 90 to the skin. In use, appropriate release liners (not shown) are removed from adhesive layers 17 and 18 and device 90 is secured to the skin of the patient. Pouches 21 and 22 are then depressed in order to fracture the liquid-containing capsules therein. The liquid released from the capsules is then introduced either directly into reservoir layers 15 and 16, or indirectly through the wicking layers 23 and 24, respectively.

Turning now to FIGS. 1 and 2, there is shown another iontophoretic agent delivery device, designated by the numeral 20. As best shown in FIG. 2, device 20 has an electronic component containing layer 14 which is preferably covered by a backing layer 13. Only the donor electrode assembly 8 is shown in the end view of FIG. 2. Donor electrode assembly 8 includes an electrode layer 11, a reservoir layer 15, and optional membrane layer 19 and ion-conducting adhesive layer 17.

Device 20 includes two layers 31 and 32 which each contain a liquid suitable for hydrating electrode assemblies 8 and 9, respectively. Layers 31 and 32 may be composed of fibrous cloth, sponge, or a hydrophilic polymer (e.g., a hydrogel) matrix material and typically comprise about 5 to 70 wt. % of the matrix material and about 30 to 95 wt. % of the hydrating liquid.

As shown in FIGS. 1 and 2, layers 31 and 32 are initially sealed between sheet 13b and sheets 33 and 34, respectively, and thereby isolated from the remaining portions of device 20. Thus, initially device 20 is separated into two portions. One portion of device 20 contains the liquid for hydrating the device and includes the hydrated layers 31 and 32, both of which are sealed between sheet 13b and sheets 33 and 34, respectively, all of which are preferably formed of a water impermeable sheet material. The other portion of device 20 is substantially non-hydrated and includes the electronic component layer 14, the electrode layers 11 and 12, the reservoir layers 15 and 16 separated by insulator 26 and optionally ion-conducting adhesive layers 17 and 18, and membrane layer 19, all of which are laminated onto sheet 13a, also of a preferably water impermeable material. A weakened score line 35 divides sheet 13a from sheet 13b.

When device 20 is ready to be used, the sheets 33 and 34 are removed. Sheet 13b is then torn or folded along score line 35 so that layers 31 and 32 are each positioned directly on sheet 13a such that layer 31 covers liquid-wicking pathways 27 and layer 32 covers liquid-wicking pathways 28. Liquid-wicking pathways 27, as best shown in FIG. 2, pass through the optional impermeable backing layer 13a, the electronic component layer 14 and the electrode layer 11. Similarly, liquid-wicking pathways 28 pass through the optional backing layer 13a, the electronic component layer 14 and the electrode layer 12. Thus, liquid-wicking pathways 27 extend from the exterior surface of sheet 13a to the top surface of reservoir layer 15 while the liquid-wicking pathways 28 extend from the exterior surface of sheet 13a to the top surface of reservoir layer 16. Once the liquid-containing layers 31 and 32 are placed over the liquid-wicking pathways 27 and 28, respectively, water from layers 31 and 32 is transported along the liquid-wicking pathways into the reservoir layers 15 and 16, as well as the optional layers 17, 18 and 19, if they are present.

The liquid-wicking pathways 27 and 28 can take several forms. Pathways 27 and 28 may be in the form of open holes running through layers 13, 14 and 11 or 12, as shown in FIG. 2. Alternatively, pathways 27 and 28 may be in the form of holes which are filled with a liquid-wicking material which is effective to quickly wick liquid from gel layers 31 and 32 into reservoir layers 15 and 16, respectively. Alternatively, pathways 27 and 28 may be formed by mixing a sufficient quantity of a hydrophilic polymer of the type used as the reservoir 15 and 16 matrices into layers 13a, 14 and 11. Generally, at least about 10 wt. % and preferably at least about 20 wt. % (on a dry weight basis) of a layer must be comprised of a hydrophilic polymer in order to provide sufficient water wicking pathways through the layer. Thereafter, a release liner (not shown) is removed from adhesive layers 17 and 18 and the device 20 is placed on a body surface 100 as shown in FIG. 2. FIG. 2 is an end view of device 20 and accordingly shows only the layered configuration of the "donor" electrode assembly. It will be understood that device 20, in its assembled condition, likewise contains an insulator 26 and a counter electrode assembly 9.

FIG. 3 shows an end view of an alternate iontophoretic drug delivery device 20a, similar to device 20 shown in FIGS. 1 and 2. In device 20a, the liquid-containing layers 31 and 32 are on the opposite side of sheet 13b from that shown in FIG. 2. Before use, the sheet 13b is separated from sheet 13a by tearing along score line 35. The liquid-containing layers 31 and 32 are then removed from sheet 13b and placed over liquid-wicking pathways 27 and 28, respectively. The liquid from layers 31 and 32 is then wicked along pathways 27 and 28 in order to hydrate the various nonhydrated components in device 20a.

FIGS. 4 and 5 illustrate another iontophoretic delivery device designated by the numeral 50. As best shown in FIG. 5, device 50 is initially in two parts. The upper part includes the electronic component layer 14 and the electrode layers 11 and 12. The lower part includes the agent reservoir layers 15 and 16, liquid-containing pouches 21 and 22, insulator 26, and optional layers such as membrane layer 19, ion-conductive adhesive layers 17 and 18 and release line 38.

As best shown in FIG. 4, the bottom portion of device 50 comprises a T-shaped release liner 25 having a weakened score line 29. Agent reservoir layers 15 and 16, or optionally adhesive layers 17 and 18 if they are present, are releasably attached to the release liner 25. In addition, liquid-containing pouches 21 and 22 and insulator 26 are attached to the lower portion of release liner 25 below the score line 29. In this configuration, pouches 21 and 22 are isolated from reservoir layers 15 and 16. In the event that liquid leaks or otherwise is inadvertantly released from the pouches, there is little danger of prematurely hydrating the electrode layers.

The device 50 can be packaged with the upper and lower portions separately packaged, or together with the upper portion resting on top of the lower portion but with the water-containing pouches 21 and 22 in the position shown in FIG. 4.

Before use, the lower portion of device 50 is reconfigured by folding or tearing release liner 25 along score line 29. The liquid-containing pouches 21 and 22 are thereby moved into position between agent reservoir layers 15 and 16. In this position, the pouches 21 and 22 are in fluid communication with reservoir layers 15 and 16, respectively. The upper portion of device 50 is then pressed downwardly, as shown by the arrows in FIG. 5, allowing pins 36 and 37 to puncture the liquid-containing pouches 21 and 22, respectively. The liquid from pouch 21 is then wicked by wicking layer 23 into the non-hydrated electrode assembly 8 in order to hydrate reservoir layer 15, and optionally membrane layer 19 and adhesive layer 17. Likewise, liquid from the pouch 22 is wicked by wicking layer 24 into the non-hydrated electrode assembly 9 to hydrate the reservoir layer 16 and optionally the adhesive layer 18.

In this embodiment, reservoir layers 15 and 16 are preferably comprised of a material which becomes tacky once hydrated, e.g., a tacky hydrogel. Alternatively, the top surface of reservoir layers 15 and 16 can also be coated with a water-conducting and ion-conducting adhesive layer.

Electrical contact between reservoir layers 15 and 16 and electrode layers 11 and 12, respectively, is maintained due to the tacky nature of layers 15 and 16, or alternatively by an adhesive applied on the top surfaces of layers 15 and 16. Thereafter, release liner 38 is removed from adhesive layers 17 and 18 and the device 50 is placed on a body surface for delivery of beneficial agent therethrough.

Device 50 illustrated in FIGS. 4 and 5 has particular utility when the matrices of reservoirs 15 and 16 are composed, in whole or in part, of a hydrophilic material having a tendency to swell as it absorbs the hydrating liquid. This embodiment has particular advantage when using hydrophilic hydrogels as the matrices of reservoir layers 15 and 16, since hydrogels have a tendency to swell during hydration. Most preferably, the top portion of device 50 is secured onto the bottom portion of device 50 after reservoir layers 15 and 16 have been completely hydrated and are no longer swelling.

When used in connection with the reservoir 15 or the donor electrode assembly 8, the term "agent" refers to beneficial agents, such as drugs, within the class which can be delivered through body surfaces. The expression "drug" is intended to have a broad interpretation as any therapeutically active substance which is delivered to a living organism to produce a desired, usually beneficial, effect. In general, this includes therapeutic agents in all of the major therapeutic areas including, but not limited to, anti-infectives such as antibiotics and antiviral agents, analgesics and analgesic combinations, anesthetics, anorexics, antiarthritics, antiasthmatic agents, anticonvulsants, antidepressants, antidiabetic agents, antidiarrheals, antihistamines, anti-inflammatory agents, antimigraine preparations, antimotion sickness preparations, antinauseants, antineoplastics, antiparkinsonism drugs, antipruritics, antipsychotics, antipyretics, antispasmodics, including gastrointestinal and urinary, anticholinergics, sympathomimetrics, xanthine derivatives, cardiovascular preparations including calcium channel blockers, beta-blockers, antiarrythmics, antihypertensives, diuretics, vasodilators, including general, coronary, peripheral and cerebral, central nervous system stimulants, cough and cold preparations, decongestants, diagnostics, hormones, hypnotics, immunosuppressives, muscle relaxants, parasympatholytics, parasympathomimetrics, proteins, peptides, psychostimulants, sedatives and tranquilizers.

The invention is particularly useful in the controlled delivery of peptides, polypeptides, proteins, macromolecules and other drugs which have a tendency to be unstable, hydrolyzed, oxidized, denatured or otherwise degraded in the presence of the liquid, such as water, necessary to conduct iontophoresis. For example, drugs containing either an ester bond (i.e., steroids) or an amide bond (i.e., peptides) may be hydrolyzed in water. Specific examples of drugs which can become degraded in the presence of water include catachols, such as apomorphine and epinephrine, salbutamol, sulfhydryls such as captopril, niphedipine, and peptides such as VIP and insulin.

Examples of other peptides and proteins which may be delivered using the device of the present invention include, without limitation, LHRH, LHRH analogs such as buserelin, gonadorelin, naphrelin and leuprolide, GHRH, insulin, heparin, calcitonin, endorphin, TRH, NT-36 (chemical name: N=[[(s)-4-oxo-2-azetidinyl]carbonyl]-L-histidyl-L-prolinamide), lipresin, pituitary hormones (e.g., HGH, HMG, HCG, desmopressin acetate, etc.), follicle luteoids, .alpha.ANF, growth factor releasing factor (GFRF), .alpha.MSH, somatostatin, bradykinin, somatotropin, platelet-derived growth factor, asparaginase, bleomycin sulfate, chymopapain, cholecystokinin, chorionic gonadotropin, corticotropin (ACTH), erythropoietin, epoprostenol (platelet aggregation inhibitor), glucagon, hyaluronidase, interferon, interleukin-2, menotropins (urofollitropin (FSH) and LH), oxytocin, streptokinase, tissue plasminogen activator, urokinase, vasopressin, ACTH analogs, ANP, ANP clearance inhibitors, angiotensin II antagonists, antidiuretic hormone agonists, antidiuretic hormone antagonists, bradykinin antagonists, CD4, ceredase, CSF's, enkephalins, FAB fragments, IgE peptide suppressors, IGF-1, neurotrophic factors, parathyroid hormone and agonists, parathyroid hormone antagonists, prostaglandin antagonists, pentigetide, protein C, protein S, renin inhibitors, thymosin alpha-1, thrombolytics, TNF, vaccines, vasopressin antagonist analogs, alpha-1 anti-trypsin (recombinant).

When used in connection with the reservoir 16 and/or the counter electrode assembly 9, the term "agent" refers to any suitable pharmacologically acceptable electrolyte salt. Suitable electrolyte salts include water soluble and biocompatible salts such as sodium chloride, alkali metal salts, alkaline earth metal salts such as chlorides, sulfates, nitrates, carbonates, phosphates, and organic salts such as ascorbates, citrates, acetates and mixtures thereof.

Electrodes 11 and 12 are electrically conductive and may be formed of a metal, or other electrically conductive material. For example, electrodes 11 and 12 may be formed of a metal foil or metal deposited or painted on a suitable backing. Examples of suitable metals include silver, zinc, silver/silver chloride, aluminum, platinum, stainless steel, gold and titanium. Alternatively, the electrodes 11 and 12 may be formed of a polymer matrix containing a conductive filler such as a metal powder, powdered graphite, carbon fibers or other known electrically conductive filler material. The polymer based electrodes may be made by mixing the conductive filler in a preferably hydrophobic polymer matrix. For example, zinc powder, silver powder, silver/silver chloride powder, powdered carbon, carbon fibers and mixtures thereof can be mixed in a hydrophobic polymer (e.g., an ethylene vinyl acetate copolymer) matrix, with the preferred amount of conductive filler being within the range of about 30 to 90 vol% and the remainder being the hydrophobic polymer matrix.

Electrodes 11 and 12 are electrically connected to the power source in layer 14 using well known means, e.g., printed flexible circuits, metal foils, wires or by direct contact. As an alternative to a battery as the power source, device 10 can be powered by a galvanic couple formed by the donor electrode 11 and counter electrode 12 being composed of dissimilar electrochemical couples and being placed in electrical contact with one other. Typical galvanic couple materials for delivering a cationic agent include a zinc donor electrode 11 and a silver/silver chloride counter electrode 12. A Zn-Ag/AgCl galvanic couple provides an electrical potential of about 1 volt.

The optional wicking layers 23 and 24 may be comprised of liquid-wicking materials such as cotton, sponges, cellulose triacetate, rayon polyesters, hydrophilic polymer resins, etc. and blends thereof. Optionally, the passageways 21 and 22 may be filled with the same or similar liquid-wicking material.

The matrix of reservoirs 15 and 16 can be any material adapted to absorb and hold a sufficient quantity of liquid therein in order to permit transport of agent therethrough by iontophoresis. For example, gauzes made of cotton or other absorbent fabrics as well as pads and sponges, both natural and synthetic, may be used. Most preferably, the matrix of reservoirs 15 and 16 is composed, at least in part, of a hydrophilic polymer material. Both natural and synthetic hydrophilic polymers may be used. Suitable hydrophilic polymers include polyvinylpyrrolidones, polyvinyl alcohol, polyethylene oxides such as Polyox.RTM. manufactured by Union Carbide Corp., Carbopol.RTM. manufactured by BF Goodrich of Akron, Ohio; blends of polyoxyethylene or polyethylene glycols with polyacrylic acid such as Polyox.RTM. blended with Carbopol.RTM., polyacrylamide, Klucel.RTM., cross-linked dextran such as Sephadex (Pharmacia Fine Chemicals, AB, Uppsala, Sweden), Water Lock.RTM. (Grain Processing Corp., Muscatine, Iowa) which is a starch-graft-poly(sodium acrylate-coacrylamide) polymer, cellulose derivatives such as hydroxyethyl cellulose, hydroxypropylmethylcellulose, low-substituted hydroxypropylcellulose, and cross-linked Na-carboxymethylcellulose such as Ac-Di-Sol (FMC Corp., Philadelphia, Penna.), hydrogels such as polyhydroxyethyl methacrylate (National Patent Development Corp.), natural gums, chitosan, pectin, starch, guar gum, locust bean gum, and the like, along with blends thereof. Of these, polyvinylpyrrolidones are preferred.

Optionally, the matrix of reservoirs 15 and 16 may also contain a hydrophobic, preferably heat fusible, polymer in order to enhance the lamination of reservoirs 15 and 16 to the adjacent layers. Suitable hydrophobic polymers for use in the matrix of reservoirs 15 and 16 include, without limitation, polyethylene, polypropylene, polyisoprenes and polyalkenes, rubbers, copolymers such as Kraton.RTM., polyvinylacetate, ethylene vinyl acetate copolymers, polyamides such as nylons, polyurethanes, polyvinylchloride, acrylic or methacrylic resins such as polymers of esters of acrylic or methacrylic acid with alcohols such as n-butanol, butanol, n-pentanol, isopentanol, 2-methyl butanol, 1methyl butanol, 1-methyl pentanol, 2-methyl pentanol, 3-methyl pentanol, 2-ethyl butanol, isooctanol, n-decanol, or n-dodecanol, alone or copolymerized with ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-alkoxymethyl acrylamides, N-alkoxymethyl methacrylamides, N-tert-butylacrylamide, and itaconic acid, N-branched alkyl maleamic acids wherein the alkyl group has 10-24 carbon atoms, glycol diacrylates, and blends thereof. Most of the above listed hydrophobic polymers are heat fusible. Of these, ethylene vinyl acetate copolymers are preferred.

When the drug or electrolyte is present in the reservoir matrix before hydration, blending of the drug or electrolyte with the hydrophilic polymer matrix components can be accomplished mechanically, either by milling, extrusion or hot melt mixing, for example. The resulting reservoir layers may then be prepared by solvent casting, extrusion or by melt processing, for example. In addition to the drug and electrolyte, the reservoirs 15 and 16 may also contain other conventional materials such as dyes, pigments, inert fillers, and other excipients.

Insulator 26 is preferably formed of a hydrophobic non-conducting polymeric material which is impermeable to both the passage of ions and water. Preferred insulating materials are nonporous ethylene vinyl acetate and closed cell foamed plastics.

The combined skin-contacting areas of electrode assemblies 8 and 9 can vary from less than 1 cm.sup.2 to greater than 200 cm.sup.2. The average device 10 however, will have electrode assemblies with a combined skin-contacting area within the range of about 5 to 50 cm.sup.2.

Having thus generally described our invention and described in detail certain preferred embodiments thereof, it will be readily apparent that various modifications to the invention may be made by workers skilled in the art without departing from the scope of this invention and which is limited only by the following claims.