Implantatable component having an accessible lumen and a drug release capsule for introduction into same

A method for delivering drugs from an implantable medical device to an implantee, comprising implanting the medical device having a receptacle configured to receive a drug release capsule, the drug release capsule having at least one drug disposed thereon, placing the drug release capsule in the receptacle subsequent to the implanting, and permitting the release of the at least one drug from the drug release capsule to the recipient.

BACKGROUND

1. Field of the Invention

The present invention relates generally to implantable medical devices, and more particularly, to a drug release capsule for implantation into an accessible lumen of an implantable medical device.

2. Related Art

Medical devices having one or more partially or completely implantable components, generally referred to as implantable medical devices, have provided a wide range of therapeutic benefits to patients over recent decades. One type of implantable medical device that has provided substantial benefits to patients over the years is a prosthetic hearing device. Prosthetic hearing devices process ambient sound to provide hearing ability to a hearing impaired patient.

Prosthetic hearing devices include a category of implantable devices known as cochlear™ implants (also referred to as cochlear™ devices, cochlear™ implant devices, and the like; “cochlear implants” herein). (COCHLEAR is a trademark of Cochlear Limited, Lane Cove, NSW, Australia.) Cochlear implants include an array of stimulation electrodes which is implanted in the cochlea of the patient (referred to herein as a recipient). The electrode array is controlled by an electronic system encased in a hermetically sealed, biocompatible housing implanted in the recipient. The electronic system, commonly referred to as a stimulator unit, essentially contains decoder and driver circuits for the stimulation electrodes. Acoustic sound reception and conversion of acoustic signals into electrical signals typically occurs in a sound processor typically worn by the recipient. The sound processor superimposes the preprocessed signals, properly coded, on a high frequency carrier signal which is transmitted transcutaneously to the stimulator unit through the closed skin. A sound input device such as a microphone converts ambient sound into representative electrical signals for processing by the sound processor. The sound input device is typically located outside of the recipient's body such as in a behind-the-ear housing worn on the auricle.

Traditionally, there has been interest in delivering a bioactive substance, pharmaceutical or chemical (collectively and generally referred to as a “drug” herein) in conjunction with implantable medical devices for a variety of purposes. For example, in one conventional approach an implantable medical device is coated with a drug. This and other conventional approaches typically require the incorporation of the drug into the implantable medical device during the manufacturing process of the device.

SUMMARY

In accordance with one aspect of the present invention, a drug delivery system comprising: an implanted component having an accessible lumen and one or more drug release ports fluidically coupling the lumen with an exterior environment of the implanted component; and a drug-delivery capsule that carries at least one drug and is configured to release the at least one drug, wherein the capsule and lumen are correspondingly configured such that the capsule may be introduced into the lumen so that when the drug-delivery capsule releases the at least one drug, the at least one drug may travel through the lumen and exit the implantable component via at least one of the one or more drug release ports.

DETAILED DESCRIPTION

Aspects of the present invention are generally directed to a drug delivery system for delivering a drug in connection with an implanted component having an accessible lumen. The implantable component may be a component of an implantable medical device. For example, the component may be a cochlear implant electrode assembly that has a lumen for receiving a stylet. In addition to the lumen of the implantable component, the drug release system comprises a drug release capsule that carries a drug. The capsule and lumen are correspondingly configured such that the capsule may be introduced into the lumen, advanced to a desired position in the lumen, and securely retained within the lumen. Because the implantable component and the drug release capsule are physically distinct, the component and capsule may be independently-manufactured, and the drug release capsule may be joined with the implantable component subsequent to the device's manufacture and/or sterilization of the component, and prior to, concurrently with, or subsequent to the implantation of the implantable medical device component.

Manufacturing a drug release capsule separately from the implantable medical device component provides flexibility in the applied therapy while reducing the undesirable aspects associated with integrating drugs in implantable medical devices. For example, embodiments of the present invention may enable manufacturing efforts to be focused solely on the successful manufacture of the medical device component rather than on manufacturing an integrated assembly of the component and drug-delivery mechanism. This may result in reduced manufacturing costs, reduced drug yield loss, reduced handling and contamination of drugs, and other benefits. Furthermore, this may allow for the manufacturing of the drug release capsule to be outsourced to specialist manufacturers. Such outsourcing may provide further benefits such as the reduction of the cost of research and development by outsourcing to manufacturers that already have regulatory approval for the desired drugs, thus allowing faster and better provision of the medical devices incorporating the drug release capsules to the relevant market. Additionally, by manufacturing the drug release capsule separately from the device itself, the implantable medical device may be utilized as a universal device having a standardized lumen that may be loaded with different embodiments of the drug release capsules. This advantageously enables a single implantable device to be manufactured and inventoried without being restricted to operating with a single drug or specific combination or dosage of drugs. This is particularly advantageous in those circumstances in which the drug to be delivered via the drug release capsule has a limited shelf life.

As used herein, the term “drug” refers to any bioactive substance or chemical now or later developed, including, but not limited to, pharmaceuticals and other chemical compounds such as those intended to provide therapeutic benefits to, or other reactions in, an implant recipient, whether localized or distributed throughout the recipient. Such drugs may include, for example, steroids or other anti-inflammatory drugs to reduce inflammation at the implantation site. Other drugs that may be included in the drug release capsules are antibiotics to mitigate bacterial growth related to the implantation of the medical device component. It should be appreciated that as used herein the term “drug release capsule” refers to any mass of material suitable for carrying a desired one or more drugs for subsequent release into the recipient, and which is configured to be introduced into and securely positioned within a lumen of the implantable medical device component. The more common definition of a capsule in the field of pharmacology; that is, a gelatinous case enclosing a dose of medicine, is just one of a myriad of embodiments of the drug release capsule of the present invention. This is described in greater detail below.

FIG. 1is a perspective view of an exemplary implantable medical device in which embodiments of a drug release system of the present invention may be implemented. In fully functional human hearing anatomy, outer ear101comprises an auricle105and an ear canal106. A sound wave or acoustic pressure107is collected by auricle105and channeled into and through ear canal106. Disposed across the distal end of ear canal106is a tympanic membrane104which vibrates in response to acoustic wave107. This vibration is coupled to oval window or fenestra ovalis110through three bones of middle ear102, collectively referred to as the ossicles111and comprising the malleus112, the incus113and the stapes114. Bones112,113and114of middle ear102serve to filter and amplify acoustic wave107, causing oval window110to articulate, or vibrate. Such vibration sets up waves of fluid motion within cochlea115. Such fluid motion, in turn, activates tiny hair cells (not shown) that line the inside of cochlea115. Activation of the hair cells causes appropriate nerve impulses to be transferred through the spiral ganglion cells and auditory nerve116to the brain (not shown), where they are perceived as sound. In certain profoundly deaf persons, there is an absence or destruction of the hair cells. Cochlear implants such a cochlear implant120is utilized to directly stimulate the ganglion cells to provide a hearing sensation to the recipient.

FIG. 1also shows the positioning of cochlear implant120relative to outer ear101, middle ear102and inner ear103. Cochlear implant120comprises external component assembly122which is directly or indirectly attached to the body of the recipient, and an internal component assembly124which is temporarily or permanently implanted in the recipient. External assembly122comprises microphone125for detecting sound which is outputted to a behind-the-ear (BTE) speech processing unit126that generates coded signals which are provided to an external transmitter unit128, along with power from a power source129such as a battery. External transmitter unit128comprises an external coil130and, preferably, a magnet (not shown) secured directly or indirectly in external coil130.

Internal component assembly124comprise an internal coil132of a stimulator unit134that receives and transmits power and coded signals received from external assembly122to other elements of stimulator unit134which apply the coded signal to cochlea115via an implanted electrode assembly140. Electrode assembly140enters cochlea115at cochleostomy region152and has one or more electrodes150positioned on an electrode array144to be substantially aligned with portions of tonotopically-mapped cochlea115. Signals generated by stimulator unit134are typically applied by an array144of electrodes150to cochlea115, thereby stimulating auditory nerve116.

Given the coiled shape of cochlea115, electrode carrier member142is typically constructed using a material, or combination of materials, which curls or is capable of being curled in a manner which follows the curvature of cochlea115. The portion of electrode assembly140intended to be inserted into cochlea115will often have a stiffening stylet (not shown) inserted into a channel, for example a lumen (not shown), which extends distally from the proximate end of electrode carrier member142. During implantation of electrode assembly140, the stylet contained in the lumen of carrier member142is removed from the proximate end of the carrier member as the carrier member is inserted into cochlea115. The act of removing the stiffening stylet from the lumen allows electrode carrier member142to curl. In further embodiments of cochlear implant120, the stiffness of the stylet decreases in response to fluids and/or body temperature allowing electrode carrier member142to curl in order to follow the curvature of the inner walls of cochlea115. In other embodiments of cochlear devices, electrode carrier member142is naturally straight without the assistance of a stylet inserted into the lumen. Such embodiments of electrode carrier member142are constructed using a flexible material, or is constructed so as to flex upon a fixed amount of force being exerted on the tip or body of electrode carrier member142as it is being inserted into cochlea115.

As one of ordinary skill in the art will appreciate, embodiments of the present invention may be advantageously implemented in a variety of implantable components. In the exemplary application above of cochlear implant120, the implantable component is electrode carrier member142which is permanently implanted in cochlea115of a recipient.

Embodiments of a drug release system of the present invention is described next below with reference toFIGS. 2A through 2D.FIG. 2Ais a side view of an embodiment of electrode carrier member142, referred to herein as electrode assembly200.FIGS. 2B-2Dare cross-sectional views of electrode assembly200taken along their respective cross-sectional lines shown inFIG. 2A. A perspective view of an exemplary embodiment of a drug-delivery capsule of the present invention is illustrated inFIG. 3.

Drug-delivery capsule300is substantially cylindrical in shape and is constructed and may take on any form to retain and release one or more drugs into lumen224. In one embodiment, drug-delivery capsule300may be formed by impregnating the drug in a ceramic or a polymer material that is configured to release the drug at a predetermined rate.

Electrode assembly200comprises an elongate carrier member220on which an electrode array244of electrodes250is disposed. As noted, each electrode250is constructed and arranged to deliver a stimulating signal to a particular region of cochlea115.

It has been found that the magnitude of the currents flowing from electrodes250, and the intensity of the corresponding electric fields, are a function of the distance between electrodes250and the modiolus (not shown) of cochlea115. If this distance is relatively great, the threshold current magnitude must be larger than if this distance is relatively small. Moreover, the current from each electrode250may flow in a number of directions, and the electrical fields corresponding to adjacent electrodes may overlap, thereby causing cross-electrode interference. To reduce such adverse effects, it is advisable to maintain a minimal distance between carrier member220and the modiolus. This is best accomplished by providing carrier member220in a shape which generally follows the shape of the modiolus, or inside wall of cochlea115(FIG. 1). This increases the effectiveness of the delivery of electrical stimulation to auditory nerve116(FIG. 1).

In this exemplary application, to position electrodes250adjacent the inside wall of cochlea115, carrier member220adopts a curled or spiral position immediately following implantation into cochlea115. It is also desirable that carrier member220be shaped such that the insertion process causes minimal trauma to the sensitive structures of cochlea115. As such, carrier member220is manufactured to be pre-curved. Specifically, carrier member220is manufactured to have a spiral configuration; that is, one or more concentric circles that approximate the curvature of cochlea115as shown inFIG. 2A.

Usually carrier member220is held in a generally straight configuration at least during the initial stages of the insertion procedure, conforming to the natural shape of cochlea115once implantation is complete. To have carrier member220assume a generally straight configuration, a lumen224is provided in the carrier member. In the illustrative application of carrier member220, lumen224extends through a substantial length of a lower extension205of carrier member220.

Lumen224is configured to receive a stiffening element230commonly referred to in the context of prosthetic hearing implants as a stylet. Although such reference is used in connection with prosthetic hearing devices, it should be appreciated that the term “stylet” is not limiting to any particular application or configuration.

Prior to implanting carrier member220, stylet230is inserted into lumen224to maintain the carrier member in a relatively straight configuration. While electrode assembly200is inserted through cochleostomy152(or the oval window of the cochlea, not shown), a surgeon biases forward carrier member220on stylet230to allow carrier member220to return to its spiral configuration and, in doing so, to follow the curvature of cochlea115. In other words, during insertion, stylet230is withdrawn from lumen224thereby allowing carrier member220to return to its pre-curved configuration.

In one embodiment, the technique for implanting electrode assembly200is the Advance Off-Stylet™ technique for the Contour™ Advance electrode (previously referred to as the Contour™ Electrode with Softip). In a another embodiment, electrode assembly200includes a Contour™ Advance Electrode, also described as Contour™ Electrode with Softip, Modified Tip, or Ski Tip. In another embodiment, the stylet is an Arrow Stylet, Surgical Stylet, or Surgical Ball Stylet. In these and other stylets and electrode carrier members, the stylet is removably inserted into lumen224of the carrier member prior to implantation, and is removed from the carrier member during implantation.

FIGS. 2C and 2Dare cross-sectional views of electrode assembly200taken along cross-sectional lines2C-2C and2D-2D inFIG. 2A.FIGS. 2C and 2Dare schematic representations of two exemplary embodiments of drug release ports240which may be implemented in carrier member220to fluidically couple lumen224with an exterior environment of electrode assembly200. In the illustrative application shown inFIG. 1, for example, such external environment is one of the ducts of cochlea115. In the exemplary embodiments illustrated inFIGS. 2C and 2D, drug release ports240are in the form of a narrow channel or opening in carrier member220. For example, in the embodiment illustrated inFIG. 2C, a drug release port240extends from lumen224with the exterior surface of carrier member220which opposes the side of carrier member220on which electrodes250are disposed. As such, drug release port240fluidically couples lumen224with the exterior environment of electrode assembly200toward the lateral wall of cochlea115when electrode assembly200is implanted in the cochlea. As another example, in the embodiment illustrated inFIG. 2D, two drug release ports240A and240B are formed in carrier member220on laterally-opposing sides of lumen224. It should be appreciated that the location, configuration, dimensions, and quantity of drug release ports240may vary depending on the particular application, type, configuration and quantity of the drug-delivery capsule and other factors such as the rate at which the capsule releases the drug, the molecular characteristics of the drug, and so on.

Drug release ports240may be passageways or channels within carrier member220as shown inFIGS. 2C and 2D. It should be appreciated, however, that in other embodiments, drug release ports240are implemented as a permeable structure within a membrane which makes up at least a part of electrode carrier member within carrier member220. Such drug release ports240allow drugs to move into cochlea115in the absence of a gross movement of fluid. In addition to permitting the flow of drugs into cochlea115, drug release ports240may be configured to control the rate of drug flow into cochlea115. In alternative embodiments, drug release ports240may be controllable. For example, in one specific embodiment, drug release ports240are responsive heat, adjusting the permeability in response to an applied heat source.

FIG. 5Ais a partial view of cochlea115implanted with an embodiment of electrode assembly200illustrated inFIG. 2A. in which the electrode assembly has a lumen with multiple portholes240, in accordance with embodiments of the present invention.FIG. 5Bis the same view of electrode assembly200shown in the same implanted position as inFIG. 5Awith a drug release capsule300positioned within the lumen, in accordance with embodiments of the present invention.FIG. 5Cis an enlarged view of cochlea115and electrode assembly200showing the release of drugs through multiple portholes240disposed on the electrode assembly.

In the exemplary embodiment of electrode assembly200illustrated inFIGS. 5A-5D, multiple portholes240are formed in carrier member220circumferentially around lumen224, providing a passageway from lumen224to locations exterior of electrode assembly200. It is to be understood, however, that drug delivery ports240may be disposed along any portion of the perimeter or circumference of electrode carrier member within carrier member220.

Electrode assembly200is implanted in a recipient by inserting electrode carrier member within carrier member220through, for example, cochleostomy region152which is formed in a portion of the recipient's cochlea115. Lumen224, as noted, is manufactured as a hollow channel inside electrode carrier member within carrier member220and terminates at an opening404at or near cochleostomy region152, inside cochlea115. Lumen224is configured to receive and securely retain a correspondingly-configured drug release capsule300(FIG. 3) as shown inFIG. 2C.

Although lumen224is depicted inFIG. 5Aas starting from a location which is inside cochlea115just beyond cochleostomy region152, and which extends along a substantial length of electrode assembly200, it is to be understood that lumen224may extend along electrode carrier member220starting from and ending at any point along electrode carrier member220. For example, in one embodiment, lumen224extends along electrode assembly200from outside cochlea115to inside the cochlea when the device is implanted in the cochlea. As such, electrode carrier member220may be configured so that opening404for lumen224is located outside cochlea115when the carrier member is implanted in cochlea115. In such an embodiment, a plug or other type of seal may be used to provide an impermeable obstruction to prevent cochlea fluids from leaking out of cochlea115. It is also to be understood that electrode assembly200may be of various lengths and extend into cochlea115to different depths. It is also to be understood that although it is noted above that electrode carrier member220is preferably configured to be adjacent to the perimodiolar wall of cochlea115upon insertion, or may be configured to follow the lateral wall of cochlea115.

As best illustrated inFIG. 2D, as drug release capsule300releases the drug it is carrying, the drug travels through lumen224and exists the lumen through one or more ports240, as illustrated by arrows502.

FIG. 2Dalso depicts a recess208configured to receive and securely retain a drug release capsule300inserted into lumen224. Drug release capsule300is inserted inside lumen224of electrode carrier member220through opening404of lumen224. As shown inFIG. 2D, a plurality of ports240are disposed in various regions of electrode carrier member220to provide a path of travel for bodily fluids (not shown), heat energy (not shown), and drugs disposed on drug release capsule300to travel between lumen224and inner areas of cochlea115, indicated by arrows2D inFIG. 2A. In one embodiment, drug release capsule300interacts with fluids present in cochlea115, which enters lumen224through ports240, to release drugs carrier by drug release capsule300into the fluids. The resulting fluid and drug mixture travels out of lumen224through ports240into cochlea115. In addition to providing localized benefits to the recipient's cochlea, it is to be understood that the drugs carrier by drug release capsule300and released into the recipient in the manner described above may also provide general benefits or benefits to other parts of the recipient's body remote from cochlea115.

As depicted inFIG. 4A, in some embodiments of the present invention, the interior walls of electrode carrier member220that define lumen224may have one or more tabs402A,402B configured to receive and securely retain drug release capsule300inserted into lumen224. For example, in one embodiment, drug release capsule300is securely retained in the lumen between tabs402due to the respective dimensions of the tabs and capsule. Alternatively, drug release capsule300is securely retained in lumen224due to a compression fit. Alternatively, a recess, rough edges, and the link may be formed in lumen224to facilitate retaining capsule300in a desired position in lumen224. In such embodiments the drugs carried by drug release capsule300interact with body fluids and/or temperature so that the drugs are carried out through various portholes240. Inserting drug release capsules300so as to be positioned securely at a desired location within recesses208inside lumen224of electrode carrier member220may be beneficial for keeping lumen24free of any objects while allowing drugs to escape from lumen224, through ports240.

In other embodiments of the present invention, ports240may be dimensioned and/or arranged along electrode carrier member220to attain a desired outcome with or without a specialized drug release capsule configuration. For example, ports240disposed closer to drug release capsule300, when drug release capsule300is inserted into lumen224, may be configured to be smaller than ports240that will be further from the implanted position of drug release capsule300. Such a configuration may beneficially direct the same amount of drugs to escape from those ports240that are further away from drug release capsule300as would escape from ports240that are closer to drug release capsule300. Alternatively, by dimensioning all portholes along electrode carrier member220to be of the same size, more drugs may be delivered to ports240that are nearer to drug release capsule300as compared to ports240that are further from drug release capsule300. Additionally, ports240may generally be designed to be smaller in one embodiment of drug release system200than in other embodiments of the present invention for the purpose of reducing the amount of drugs released from drug release system200, as described above. For example, as part of a miniaturization effort for making these implantable devices more sophisticated or smaller for better suited for implantation in a recipient, drug release capsule300is highly concentrated with the drugs disposed thereon. Depending on the amount or rate of discharge desired, portholes204may be configured to have larger or smaller openings, as shown inFIG. 5D, or to have thicker or thinner sidewall thicknesses, which will impact the rate, volume or type of interaction permitted between drug release capsule300and body fluids or heat energy, in order to achieve the desired amount or rate of discharge from drug release system200.

In certain embodiments of the present invention, drug release capsule300is maintained in place after being inserted into lumen224by retention tab402, as shown inFIGS. 4A and 4B.FIG. 4Ais a partial view of an embodiment in which retention tabs402A and402B maintain drug release capsule300in place inside electrode assembly200.FIG. 4Bis a cross-sectional view of electrode assembly200taken along section line4B-4B showing retention tab402B. Drug release capsule300is shown inserted through lumen opening404into lumen224of electrode assembly200. Retention tab402B projects inwardly into lumen224from electrode assembly140and prevents drug release capsule300from further entering lumen224by interfering with that path of travel. Retention tab402B also projects inwardly into lumen224from electrode assembly140and prevents drug release capsule300from escaping out of electrode assembly140through lumen opening404. Retention tabs402A,402B may be integrally formed with electrode assembly140, or may be separately formed attached to electrode assembly, and may be resilient to some degree. Drug release capsule300is inserted into lumen224through lumen opening205. During insertion, when sufficient force is applied to drug release capsule300, resiliently formed interference tab402B compresses or bends sufficiently to permit the continued insertion of drug release capsule300into lumen224towards interference tab402A. When fully inserted, drug release capsule300may be positioned in lumen224aligned with either or both interference tabs402A and402B such that one or both are compressed by drug release capsule300. Alternatively, interference tabs402A and402B may be positioned apart from one another such that drug release component202is situated between and apart from both interference tabs402A and402B.

Although an interference retention is described above with regard toFIGS. 4A and 4B, it is to be understood that other types of retention are possible to maintain the position of drug release capsule300when inserted into lumen224. For example, a compression retention, bonded retention, sutures, screws, clips, a combination of the above, or others may be used for such a purpose. In a compression retention, drug release capsule300is manufactured to be resilient to some degree and slightly larger than lumen224along at least a portion of lumen224. Alternatively, drug capsule300may be manufactured to be rigid and electrode assembly140having lumen224therein may be manufactured to be resilient to some degree. When inserted into lumen224, drug release component202will compress, electrode assembly140will expand, or a combination of the two will occur, so that a compression force is created between drug release capsule300and electrode assembly140, thereby securely retaining drug release capsule300in that position.

In another embodiment, the drug release capsule may be configured to be bonded into the corresponding lumen of the implantable medical device thereby eliminating the need for a non-bonded retention means (e.g., compression retention, interference retention) between the drug release capsule and the lumen of the medical device. In one embodiment, such bonding is performed in a sterile field immediately prior to surgery, for example by inserting a ring-shaped drug release capsule around a stylet that has yet to be removed from an electrode array. Alternatively, such bonding is performed after the medical device is implanted in the patient. In another embodiment, such bonding is performed during manufacturing, such as one of the last few steps of manufacturing.

In one embodiment, the above bonding is performed by disposing a glue layer on the lumen so that the drug release capsule may be pressed in prior to surgery. This may be performed manually or with a simple press-tool that aligns the two components and presses them together with a predefined amount of pressure. Alternatively, a liquid glue may be applied between the lumen surface and the drug release capsule. In one preferred embodiment, the liquid glue sets and/or cures rapidly. In another embodiment, a UV-cured glue is pre-applied to the component, or applied as a liquid, or is a separate component that is inserted between the drug release capsule and the lumen within the implantable medical device. In one embodiment, a liquid perfluoropol polymer such as that described in International Application WO 2007/021620 A2 may be utilized. International Application WO 2007/021620 A2 is hereby incorporated by reference herein. Other adhesives include, but are not limited to, fibrin glues, cyanoacrylates, polyurethane adhesives, silicone adhesives, and UC-cured acrylics. In another embodiment, chemical surface modification may be utilized to attain a desired bonding. For example, in one embodiment, covalently bonded proteins, or sulfonation may be performed to increase the wetability of the surface.

It may be desirable for embodiments of the drug release capsule of the present invention to be constructed of a resorbable material, so that while drugs are being absorbed from the lumen, or after they are absorbed, the drug release capsule may be partially or completely resorbed by the tissue surrounding the implant site. In certain embodiments, the drug release capsule is comprised of a resorbable material that partially or completely degrades over time through interaction with various body fluids. In other embodiments, the drug release capsule is comprised of a resorbable material that partially or completely degrades over time through exposure to body temperatures.

However, it may also be desirable for the drug release capsule to be constructed of a non-resorbable material. The use of a non-resorbable material may offer different benefits from the use of a resorbable material, such as the continued provision of a flush and gapless surface on one or more sides of the implantable medical device or tissue. For example, the drug release capsule may be made of a polymeric material configured to enable drugs to be embedded within the structure of the polymeric material, and to release the drugs either naturally or through the interaction of body fluids or body heat which may permeate the capsule. Furthermore, the drug release capsule may have micro-surface geometry, such as those possible through advances in nano-technologies, which may limit or inhibit bacteria growth.

It should also be appreciated that the drug release capsules described above may be formed by one or more layers or sub-parts. In other words, each drug release capsule may be a composite of multiple layers or sub-parts. Each such layer or sub-part may serve a different function, for example, being configured to carry a different drug, releasing the same or different drug at the same or different rate, or having different concentrations of a drug across one or more portions of the drug release capsule.

Furthermore, it is to be understood that drugs may be disposed on just a portion of a drug release capsule depending on the particular application. For example, it may be beneficial for a drug release capsule to have a drug disposed on only a portion of the capsule, with the remaining portion of the capsule configured merely as a carrier or supporting member for the medicated portion of the drug release capsule.

According to a further embodiment of the present invention, the drug release capsule may be constructed of a polymeric material, in which molecules or other components of a drug are disposed within the chemical structure of the drug release capsule. One example of a polymeric material which may be used to construct an embodiment of a drug release capsule of the present invention is silicone. Drugs may be disposed within the silicone drug release capsule such that the drug is released from the drug release capsule.

According to another embodiment of the present invention, the surface of the drug release capsule may be constructed to have microsurface geometry. Such a microsurface geometry may be constructed using nano-technologies, or may be constructed using other technologies presently known or developed in the future. Having a microsurface geometry may enable the drug release capsule to be useful in partially or completely inhibiting growth of bacteria and other biological organisms adjacent to the drug release capsule.

According to yet another embodiment of the present invention, drug release capsule300may be formed to be resilient to some degree, for use in situations where it is desirable to insert a soft or flexible capsule into an implanted medical device. For example, where the medical device a cochlear implant comprising electrode array144, it may be desirable to advance drug release capsule300past the first curved portion inside cochlea115. In that case, having a resilient capsule300may be useful or even necessary for such an insertion such that the outer shape of electrode array144is not deformed or otherwise unacceptably altered so as to negatively impact the operation or durability of the electrode array144and surrounding anatomy.

Conversely, drug release capsule300may be formed as a rigid capsule and used to provide or supplement the structural integrity of lumen224. For example, rigid drug release capsule300having a straight or other shape may be inserted into lumen224so that drug release capsule300provides or reinforces the shape of electrode array144surrounding lumen224through rigid drug release capsule300.

Although various embodiments of the present invention have been described herein as a single capsule, it is to be understood that embodiments in which the drug release capsule202comprise multiple components, some of which may be drug release capsules and some of which may serve other functions, are also considered a part of the present invention. Examples include, but are not limited to, a drug release capsule component carrying drugs which promote tissue growth, for example to promote, cause or support the sealing of the cochleostomy region152or oval window110. Another example is a drug release capsule component carrying drugs which promote enhanced stimulation. These and other components may be inserted into lumen224of electrode array144as described above. Other embodiments may also have an additional lumen (not shown) disposed in a portion of electrode array144configured to remain outside cochlea115near cochleostomy region152into which a drug release capsule component which promotes tissue growth may be inserted. Other drug release capsule components in the same embodiment may be inserted inside cochlea115in lumen224to provide other therapeutic benefits such as promoting enhanced stimulation. Although the components of drug release capsule202are described above as being separate from one other, it is to be understood that in other embodiments, the various drug release components carrying different types of drugs may be joined or produced as a unitary body which is inserted into lumen224.

In other embodiments, various drug release capsule components may be inserted in lumen224together and in a specific sequence so as to direct the various drugs being carried by one or more of those drug release capsule components to different locations within cochlea115. For example, a component carrying a stimulation enhancing drug may be inserted into lumen224prior to a component carrying a tissue growth promoting drug so that each drug may be directed to deeper regions in cochlea115or to cochleostomy region152, respectively, to provide the various therapeutic benefits afforded by each component. Intermediate to inserting each component into lumen224, one or more inert or other component not carrying any drugs may be inserted, to provide one or more spaces between components carrying drugs. Furthermore, one or more of these inert or other components may provide a sealing function, in order to segregate fluids, drugs and other materials from passing the sealing component in lumen224. The sealing components may be manufactured of a hygroscopic material which swells soon after being exposed to liquid so as to provide a seal inside lumen224thereby segregating the inner regions of lumen224from the portion outside the seal inside lumen224. In other embodiments, a shape memory polymer material may be used to manufacture a seal component.

FIG. 3Ais a partial perspective view of cochlea115(FIG. 1) and an embodiment of electrode assembly140of cochlear implant120(FIG. 1). As noted, in this exemplary embodiment, electrode carrier member220has a lumen224with multiple portholes206disposed therein.

FIG. 3Bis the same perspective view of cochlea115and electrode assembly140as shown inFIG. 3A, with drug release capsule300positioned in lumen224of carrier member220.

FIG. 3Cis an enlarged cross-sectional view of a portion of cochlea115and electrode assembly140.

Similarly, in the exemplary application of a cochlear implant in which the implanted component that implements embodiments of the drug release system is a fully implanted component, it should be appreciated that the present invention may be implemented in implanted medical device components that are partially implanted. These alternative embodiments and applications of the present invention are described in greater detail below.

Further features and advantages of the present invention are described in U.S. patent application Ser. No. 10/416,634, filed on Nov. 10, 2003, entitled “Apparatus For Delivery of Pharmaceuticals To The Cochlear”, which is a National Phase Application of International Application No. PCT/AU01/01479, filed Nov. 14, 2001, entitled “Apparatus For Delivery of Pharmaceuticals To The Cochlear”, which claims priority from Australian Provisional Application No. PR 1484, filed Nov. 14, 2000. This application also claims priority from U.S. Provisional Patent Application No. 60/978,572, filed Oct. 9, 2007, entitled “Drug release Capsule For Implantation Into An Accessible Lumen Of An Implanted Medical Device. The above applications are hereby incorporated by reference herein.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. All patents and publications discussed herein are incorporated in their entirety by reference thereto.