DEVICE FOR ADMINISTERING AN ACTIVE AGENT TO THE SKIN OR MUCOSA

Abstract: A transdermal drug delivery device comprising a drug formulation-containing reservoir (13) defined by a backing layer (12) and a drug-permeable membrane layer (16), a peelable inner liner (20) that underlies the reservoir and a portion of the backing/membrane outwardly of the reservoir periphery, an adhesive layer (15) that underlies the inner liner and outwardly extending portions of the membrane/backing layers, and a peelable release liner layer (17) that underlies the adhesive layer with a first permanent heat seal (18) between the backing and the membrane about the perimeter of the reservoir and another concentric peelable (impermanent) heat seal (19) between the backing and the inner liner positioned outwardly of the first heat seal, the heat seals providing barriers that isolate the drug formulation from the adhesive.

Description: This invention is in the field of transdermal/transmucosal administration of active agents (drugs). More particularly it relates to a device for achieving such administration comprising an active agent-containing reservoir and an adhesive layer for affixing the device to the skin or mucosa in which the adhesive layer is peripheral to the path of the active agent to the skin or mucosa and is protected from degradation by the components of the reservoir by a multiplicity of heat seals. There are many patents describing devices for administering drugs through the skin or mucosa. These devices are commonly in the form of a laminated composite that includes a reservoir layer containing the drug, a pressure sensitive adhesive layer for attaching the composite to the skin, and a backing layer that forms the upper layer of the device. Depending upon the particular drug and drug formulation involved, the reservoir layer may be a matrix in which the drug formulation is dispersed or a layer in the form of a walled container which holds the drug formulation. Container-type reservoirs are often formed as a pocket between the backing layer and a drug-permeable basal membrane through which the drug passes to the skin. The pressure sensitive adhesive layer normally underlies the membrane and the drug also passes through it on its way to the skin. Devices having container-type reservoirs with underlying pressure sensitive adhesive layers have significant disadvantages when one or more components of the drug formulation that are released from the reservoir to the skin are solvents for the adhesive or otherwise adversely effect the properties of the adhesive as they pass through it to the skin. In such cases those reservoir component(s) cannot be permitted to pass through the adhesive and means must be found to isolate the adhesive from them. The present invention provides a device design in which the adhesive is peripheral to the path of the drug formulation and is isolated from the drug formulation by a multiplicity of heat seals between selected layers of the device. At least one other transdermal drug delivery device design has been proposed which involves an adhesive layer that is peripheral to the path of the drug to the skin. U.S. Patent No. 4,573,996 describes a device that has both a drug-permeable adhesive layer in the path of the drug and a peripheral drug-impermeable adhesive layer that is not in the path of the drug. The purpose of the peripheral adhesive layer is to provide a site for handling the device which avoids the risks of altering the drug path or contaminating the fingers with drug. Figure 6 of the patent shows a multi-layer laminated composite composed of (1) a backing layer, (2) a drug permeable membrane underlying the backing that forms with the backing a pocket that serves as a drug-containing reservoir, (3) a drug-permeable adhesive layer directly underlying the membrane (4) a ring-shaped drug-impermeable adhesive layer adjacent and peripheral to the drug-permeable adhesive layer, and (5) a basal removable protective layer. The combination of a heat seal between the backing and the membrane at the edge of the reservoir and the peripheral drug-impermeable adhesive layer prevents radial or horizontal migration of the drug from the reservoir. This does not address the problem of keeping drug formulation components isolated from the adhesive layer. There is only a single heat seal shown and the single heat seal is not used to isolate the drug formulation from either adhesive layer. The present invention employs two peelable layers, a permanent heat seal and a peelable heat seal in a manner that permits the creation of a peripheral ring of adhesive when the two peelable layers are removed from the device. In EP-A-171800 (US-A-4695277) a device includes a reservoir for active agent between a backing layer and a membrane which is permeable to the active agent. A portion of the backing layer and of the membrane extend outwardly of the bounds of the reservoir and there is an adhesive layer on that portion. A layer which is impermeable to the active agent is heat-sealed to the backing layer inwardly of the adhesive layer, so as to prevent migration of active agent to the adhesive layer. In the present invention being defined in claim 1, a second impermeable layer lies between the first layer and the membrane, the adhesive layer being continued to cover it. There is a peelable heat seal between the backing layer and the second impermeable layer, outwardly of a heat seal between the membrane and the backing layer, both of the heat seals forming a barrier to migration of the active agent. The peel strengths between the adhesive layer and the first and second impermeable layers is greater than the strength of the peelable heat seal. Thus when the first layer is torn away by the user, the strength of the adhesive is such that this action breaks the peelable heat seal and the membrane, and a surrounding part of the adhesive layer, are exported. Until that time, migration of the active ingredient has been presented by two heat seals; and one of these remains even when the device is in use. The drawing is an enlarged sectional view of one embodiment of the device of the invention. The drawing shows a device, generally designated 22, that is an embodiment of the invention that is designed to administer an active agent formulation of a drug and/or a permeation enhancer that is a solvent for pressure sensitive adhesives that are commonly used in transdermal delivery devices. Device 22 is designed to place the adhesive out of the path of the enhancer-drug formulation and to prohibit radial or horizontal migration of the drug/enhancer into the adhesive. Device 22 is a laminated composite. The uppermost layer of the composite is a heat-sealable backing film 12 having an inverted, cup-shaped recess 13 that serves as a container or reservoir for a drug-enhancer formulation 14. Underlying the reservoir and all or a portion of the part of the backing layer outwardly of the reservoir is a membrane layer 16 that is permeable to the drug-enhancer formulation. An inner peel sealable liner 20 underlies the membrane layer and extends outwardly of the periphery of the membrane layer. The next layer in the composite is a pressure-sensitive adhesive layer 15 that underlies the inner peel sealable liner and the portion of the backing layer that extends outwardly of the edge of the liner. A first layer which is impermeable to the active agent in the reservoir is a liner 17 which covers the entire underside of the assembly and forms the basal surface of the device. There are two concentric heat seals in the composite. The first is at 18 between the outer edge of the membrane and the backing. It extends completely around the perimeter of the reservoir and forms a permanent seal between the backing film and membrane. The second is at 19 and is between the outer edge of the inner peel sealable liner and the backing layer and forms a peelable (impermanent) seal between the backing film and a second impermeable layer which is the inner liner 20. It is concentric to and outwardly of the first heat seal. These seals prevent the drug/enhancer formulation from migrating into the adhesive during storage. After the release liner 17 is removed, the first heat seal 18 prevents such migration. The width of the seals will usually be in the range of 0.1 to 1.0 cm. The peel strengths between the adhesive layer and the two sealable layers is greater than the force required to break the peelable seal at 19. Thus, when the release liner is peeled from the underside of the assembly the peelable seal is broken and the inner peel sealable liner and the portion of the adhesive between liners 17 and 20 is removed therewith leaving a peripheral ring of adhesive underlying the outer edge of the backing. When device 22 is placed into use, the release liner layer 17 and inner liner 20 are peeled away from the underside of the device and discarded. This operation directly exposes the undersurfaces of the membrane and the peripheral ring of adhesive layer and the device can be placed on a desired site on the skin or mucosa of the individual to be treated with the active agent. In the embodiment shown in the drawing the second impermeable heat seal is formed between the backing and inner liner. It will be appreciated in this regard that additional heat-sealable layers could be included in the device that are part of the backing or inner liner, as the case may be. The invention device is useful when one or more of the components of the active agent formulation is incompatible with available adhesives that are useful for removably attaching elements to the skin or mucosa. The term "incompatible" is intended to mean that through physical and/or chemical interaction of the component(s) with the adhesive the adhesiveness or other desirable properties (e.g., nonirritancy) of the adhesive are significantly destroyed or impaired. The drug itself may be such a component or a carrier, solvent, skin permeation enhancing agent or other additive may be such a component. The backing layer 12 of the device may be composed of a single film or a plurality of films. In any event, its inner surface must be capable of being heat sealed to the membrane and release liner layers of the device. One or more of the films that constitute the layer will be impermeable to components of the drug formulation contained in the reservoir. Examples of materials used as backing layers in transdermal delivery devices that may find use in the present invention are polyethylene, polypropylene, polyvinylchloride, polyethylene terephthalate, and combinations thereof. The layer may include one or more metal layers and/or one or more fibrous layers. The reservoir pocket in the backing may be formed by vacuum forming or other like methods of forming desired shapes in films. The term "drug" as used to describe the principal active ingredient of the device intends a biologically active compound or mixture of compounds that has a therapeutic, prophylactic or other beneficial pharmacological and/or physiological effect on the wearer of the device. Examples of types of drugs that may be used in the invention device are antiinflammatory drugs, analgesics, antiarthritic drugs, antispasmodics, antidepressants, antipsychotic drugs, tranquilizers, antianxiety drugs, narcotic antagonists, antiparkinsonism agents, cholinergic agonists, anticancer drugs, immunosuppression agents, antiviral agents, antibiotic agents, appetite suppressants, antiemetics, anticholinergics, antihistamines, antimigraine agents, coronary, cerebral or peripheral vasodilators, hormonal agents, contraceptive agents, antithrombotic agents, diuretics, antihypertensive agents, cardiovascular drugs, and the like. The appropriate drugs of such types are capable of permeating through the skin either inherently or by virtue of treatment of the skin with a percutaneous absorption enhancer. Because the size of the device is limited for patient acceptance reasons, the preferred drugs are those that are effective at low concentration in the blood stream. Examples of specific drugs are steroids such as estradiol, progesterone, norgestrel, levonorgestrel, norethindrone, medroxyprogestrone acetate, testosterone and their esters, nitro-compounds such as nitroglycerine and isosorbide nitrates, nicotine, chlorpheniramine, terfenadine, triprolidine, hydrocortisone, oxicam derivatives such as piroxicam, ketoprofen, mucopolysaccharidases such as thiomucase, buprenorphine, fentanyl, naloxone, codeine, dihydroergotamine, pizotiline, salbutamol, terbutaline, prostaglandins such as misoprostol and enprostil, omeprazole, imipramine, benzamides such as metoclopramine, scopolamine, peptides such as growth releasing factor and somatostatin, clonidine, dihydropyridines such as nifedipine, verapamil, ephedrine, pindolol, metoprolol, spironolactone, nicardipine hydrochloride, calcitriol, thiazides such as hydrochlorothiazide, flunarizine, sydononimines such as molsidomine, sulfated polysaccharides such as heparin fractions and the salts of such compounds with pharmaceutically acceptable acids or bases, as the case may be. Depending upon the inherent permeability of the skin to the particular drug or drugs being administered by the device, the reservoir may also contain a percutaneous absorption enhancer that increases the permeability of the skin to the drug(s) and is coadministered to the skin. Examples of percutaneous absorption enhancers are those referred to in U.S. Patents Nos. 3,989,816, 4,316,893, 4,405,616, 4,060,084, and 4,379,454 and J Pharm Sci (1975) 64 :901-024. The formulation contained in the reservoir may also include solvent(s), gelling agents, stabilizers, and other additives. As indicated previously one or more of these components or a combination of these components is incompatible with the adhesive. The membrane is permeable to the drug. It may be a "dense" membrane made of a material that is inherently permeable to the components of the reservoir that are to be administered to the skin or mucosa or it may be made of a microporous material whose pores are filled with a drug-permeable material. In the case of dense membranes, the component(s) dissolve in the material and diffuse through the material to the skin. In the case of microporous materials the component(s) diffuse through the pores to the skin. The membrane may or may not be a rate-controlling element depending upon the particular drug involved, the permeability of the skin to the drug, and the rate of delivery required to provide therapy. Examples of materials for making dense membranes are given in U.S. Patents Nos. 3,598,122 and 4,650,484. Examples of materials for making microporous membranes are provided in U.S. Patents Nos. 3,797,494 and 4,031,894. The adhesive layer is composed of a pressure sensitive surgical adhesive such as those that are commonly used to affix transdermal drug delivery devices, bandages or other dressings to the skin. Examples of such adhesives are polyisobutene, natural rubber adhesives, acrylic and methacrylic adhesives, and silicone adhesives. The release liner layer 17 and inner liner 20 may be composed of a single layer or a multiplicity of layers. They should be (1) impermeable to the components of the drug formulation that diffuse through the membrane, (2) heat sealable in the case of the inner liner, and (3) inherently strippable or peelable or rendered so by techniques such as silicon or fluorocarbon treatment. An example of a film having such properties is 3M release liner MSX-899. The respective components of the device may be formulated and assembled using procedures that are known in the drug formulation, transdermal device, and laminating arts. The shape of the device is not critical, and devices of preformed shapes may be assembled directly or punched, cut, or otherwise formed from large sheets of laminated composite. The following examples further illustrate the invention. These examples are not intended to limit the invention in any manner. Examples Example 1 A 30% by weight polyisobutene (PIB) adhesive in heptane is cast on a silanized release liner using a 0.25 mm (10 mil) gap Gardener knife. The solvent is evaporated to yield a 0.05 mm (2.0 mil) thick PIB adhesive layer. A 15 cm² circular disc is die cut from a 0.025 mm (1.0 mil) thick peel seal release liner (3M, MSX-899) and laminated to the PIB adhesive with the peel seal release surface facing out from the adhesive surface, forming laminate L1. The backing film (Scotchpak 1012) is then thermal formed to provide a 10 cm² surface area, 2 cc volume cup. A gelled pindolol HCl/permeation enhancer reservoir ointment is prepared by mixing adequate quantities of a 1/1 volume ratio of isopropyl alcohol/methyl laurate with pindolol HCl and Klucel® gelling agent (FMC) to provide a 50 mg/ml pindolol suspension containing 5% by weight Klucel® gelling agent. The gel is pipetted (2 cc) into the cup and a 0.025 mm (1.0 mil) microporous polyethylene membrane (Questar, K-861) is heat sealed around the drug reservoir cup at 340°C for 0.5 seconds. The PIB surface of laminate L1 is then laminated to the backing film such that the 15 cm² peel seal disc concentrically overlaps the 10 cm² drug reservoir cup. The backing film is then sealed to the peel seal disc of laminate L1 to form a heat seal ring, 12.5 cm² concentric with the 10 cm² drug reservoir. All heat seals are 0.1 cm wide. Final 30 cm² circular shaped systems are then die cut using a 30 cm² circular steel rule die. Systems are then pouched in paper/aluminum foil/polyethylene pouches. The 10 cm² heat seal forms a permanent seal between the backing film and the microporous membrane, thus forming the drug/enhancer reservoir. The peel seal formed between the backing film and the peel seal disc further prevents drug/enhancer migration from the reservoir into the peripheral adhesive. As long as the peel strengths between the (1) release liner and the PIB adhesive and (2) the PIB adhesive and the 15 cm² peel seal disc are greater than the force necessary to separate the peel seal between the backing film and the 15 cm² peel seal disc, the peel seal disc will be removed from the system leaving the peripheral adhesive on the edge of the backing film when the release liner is removed. Example 2 A transdermal drug delivery system is prepared as described in Example 1 using a Nicardipine HCl/enhancer reservoir gel prepared by adding Nicardipine HCl and Klucel® to a 3/2 volume ratio of isopropanol/methyl laurate in quantities sufficient to provide a 50 mg/ml Nicardipine HCl suspension concentration with 4.5% by weight Klucel®, in place of the pindolol HCl/enhancer reservoir gel. The in vitro , steady state transdermal flux of Nicardipine HCl across human cadaver skin is determined using the methods of Merritt and Cooper ( J Controlled Release (1984) 1 :161), to be 3 µg-cm²/hr. Example 3 A transdermal drug delivery system is prepared as described in Example 1 using a Calcitriol/enhancer reservoir gel, prepared by mixing sufficient amounts of Calcitriol and Klucel® with a 71%/4%/25% ethanol/methyl laurate/water tri-solvent mixture to provide a 100 µg/ml Calcitriol concentration with an 8.7% by weight Klucel® level, in place of the pindolol HCl/enhancer gel. The in vitro , steady state transdermal flux of Calcitriol across human cadaver skin is determined using the methods of Merritt and Cooper ( J Controlled Release (1984) 1 :161), to be 0.67 µg-cm²/day. Modifications of the above described modes for carrying out the invention that are obvious to those of skill in the fields of pharmaceutical chemistry, transdermal drug delivery, or related fields are intended to be within the scope of the following claims.

Claims: A device (22) for administering an active agent to the skin or mucosa of an individual comprising a laminated composite of: (a) a backing layer (12); (b) an active agent-permeable membrane (16), the backing layer (12) and membrane (16) defining (c) a reservoir (14) therebetween that contains a formulation of the active agent, said reservoir (14) having a smaller periphery than the backing layer (12) and membrane (16) such that a portion of the backing layer (12) and membrane (16) extends outwardly of the periphery of the reservoir (14); (d) an adhesive layer (15); (e) a first peelable active agent formulation-impermeable layer (17) that underlies and covers the adhesive layer (15); (f) a peelable heat seal (19) providing a barrier to migration of components of the active agent formulation from the reservoir (14) into the adhesive layer (15); characterised by: (g) having a second peelable active agent formulation-impermeable layer (20) that underlies the reservoir (14) and a portion of said outwardly extending portion of the backing layer and membrane; (h) the adhesive layer (15) underlying and covering the second peelable active agent formulation-impermeable layer (20) and the outwardly extending portion of the backing layer (12); (i) having a permanent heat seal (18) about the periphery of the reservoir (14) between the backing layer (12) and the membrane (16); and (j) the peelable heat seal (19) being outward of the permanent heat seal (18) and being between the backing layer (12) and the second peelable active agent formulation-impermeable layer (20), both heat seals (19,20) providing barriers to migration of components of the active agent formulation from the reservoir (14) into the adhesive layer (15), and the peel strengths between the adhesive layer (15) and the first and second peelable active agent impermeable layers (17,20) being greater than the force required to break the peelable heat seal (19) so that when the first peelable layer (17) is removed from the device (22) the peelable heat seal (19) is broken and the second peelable layer (20) and underlying portion of the adhesive layer (15) are also removed. The device of claim 1 wherein the adhesive (15) is incompatible with one or more of the components of the formulation that permeate through the membrane (16) to the skin or mucosa. The device of claims 1 or 2 wherein the backing layer (12) is a laminated composite of at least one layer that is impermeable to the formulation and an inner heat-sealable layer. The device of claims 1, 2 or 3 wherein the adhesive (15) is an acrylic adhesive, the active agent is pindolol hydrochloride, and the formulation includes isopropyl alcohol and methyl laurate. The device of claims 1, 2 or 3, wherein the adhesive (15) is an acrylic adhesive, the active agent is nicardipine hydrochloride, and the formulation includes isopropyl alcohol and methyl laurate. The device of claims 1, 2 or 3, wherein the adhesive (15) is an acrylic adhesive, the active agent is calcitriol and the formulation includes ethanol, methyl laurate, and water. The device of claims 1, 2, 3, 4, 5 or 6, wherein the membrane (16) is a microporous polyethylene membrane.

Inventors: CHANG, YUNIK, EBERT, CHARLES D., PATEL, DINESH C.
Applicants: THERATECH, INC.
Application year: 1988
Main classification: A61M35
IPC codes: A61M37, A61K9, A61L15