阅读说明：本技术 可生物侵蚀的药物递送装置 (Bioerodible drug delivery device ) 是由 H·郭 J·B·陈 于 2018-06-12 设计创作，主要内容包括：本发明涉及一种可生物侵蚀的药物递送装置,所述可生物侵蚀的药物递送装置能够植入患者体内需要治疗的区域处或其附近。所述可生物侵蚀的药物递送装置能够用于递送各种各样不同的药物活性剂,并且能够以受控的速率并在延长的时间段内进行所述递送。所述可生物侵蚀的药物递送装置包括可生物侵蚀的聚合物外壳与用于递送其中所含的所述药物活性剂的一个或多个递送端口。用作所述可生物侵蚀的聚合物外壳的聚合物在所述可生物侵蚀的药物递送装置中的所述药物活性剂的给药期间基本上是不降解的。本发明还提供了制造所述可生物侵蚀的药物递送装置的方法,以及使用所述可生物侵蚀的药物递送装置来治疗疾病和病症的方法。(The present invention relates to a bioerodible drug delivery device that is implantable in or near an area of a patient's body in need of treatment. The bioerodible drug delivery device can be used to deliver a wide variety of different pharmaceutically active agents, and can do so at a controlled rate and over an extended period of time. The bioerodible drug delivery device includes a bioerodible polymeric housing and one or more delivery ports for delivery of the pharmaceutically active agent contained therein. The polymer used as the bioerodible polymeric shell is substantially non-degrading during administration of the pharmaceutically active agent in the bioerodible drug delivery device. The invention also provides methods of making the bioerodible drug delivery device, and methods of using the bioerodible drug delivery device to treat diseases and conditions.)

1. An implantable bioerodible drug delivery device comprising

A drug core comprising a pharmaceutically active agent,

a bioerodible outer member including

A first bioerodible polymer substantially surrounding the drug core, wherein the first bioerodible polymer is impermeable to the pharmaceutically active agent after implantation of the device; and

at least one delivery port comprising a second bioerodible polymer that is permeable to the pharmaceutically active agent after implantation of the device; and is

Wherein the bioerodible outer member is configured to provide a substantially constant dosing rate of the pharmaceutically active agent over a predetermined treatment period after implantation.

2. The implantable bioerodible drug delivery device of claim 1 wherein the drug core comprises a third bioerodible polymer.

3. The implantable bioerodible drug delivery device of claim 1 wherein the bioerodible outer member comprises a polymer selected from the group consisting of: lactic-glycolic acid copolymers, polycaprolactone, polylactic acid, polyglycolic acid and polyvinyl alcohol and mixtures thereof.

4. The implantable bioerodible drug delivery device of claim 1 wherein the pharmaceutically active agent is selected from the group consisting of: anesthetic, anticancer agent, antifungal agent, antiviral agent, cell transport/migration preventing agent, anti-glaucoma agent, immune response modifier, peptide, protein, steroid, corticosteroid, antibacterial agent, neuroprotective agent, anti-inflammatory agent, antiallergic agent, anticholinesterase, mydriatic agent, and mydriatic agent.

5. The implantable bioerodible drug delivery device of any one of claims 1 to 4 wherein the bioerodible outer member is tubular.

6. The implantable bioerodible drug delivery device of claim 5 wherein each end of the tubular bioerodible outer member includes a delivery port.

7. The implantable bioerodible drug delivery device of claim 1 wherein the predetermined treatment period is in a range of 1 to 30 days.

8. The implantable bioerodible drug delivery device of claim 1 wherein the predetermined treatment period is in a range of one month to six months.

9. The implantable bioerodible drug delivery device of claim 1 wherein the predetermined treatment period is in a range of six months to one year.

10. The implantable bioerodible drug delivery device of claim 1 wherein the predetermined treatment period is in a range of one to three years.

11. The implantable bioerodible drug delivery device of claim 5 wherein the pharmaceutically active agent is a corticosteroid.

12. A method of treating a patient, the method comprising

Identifying a region of a patient in need of treatment;

implanting a bioerodible drug delivery device in sufficient proximity to the area in need of treatment to provide therapeutic relief, wherein the bioerodible drug delivery device comprises

A drug core comprising a pharmaceutically active agent,

a bioerodible outer member including

A first bioerodible polymer substantially surrounding the drug core, wherein the first bioerodible polymer is impermeable to the pharmaceutically active agent after implantation of the device; and

at least one delivery port comprising a second bioerodible polymer that is permeable to the pharmaceutically active agent after implantation of the device; and is

Wherein the bioerodible outer member is configured to provide a substantially constant dosing rate of the pharmaceutically active agent over a predetermined treatment period after implantation.

13. The method of treating a patient according to claim 12, wherein the drug core comprises a third bioerodible polymer.

14. The method of treating a patient according to claim 12, wherein the bioerodible outer member comprises a polymer selected from the group consisting of: lactic-glycolic acid copolymers, polycaprolactone, polylactic acid, polyglycolic acid and polyvinyl alcohol and mixtures thereof.

15. The method of treating a patient according to claim 12, wherein the pharmaceutically active agent is selected from the group consisting of: anesthetic, anticancer agent, antifungal agent, antiviral agent, cell transport/migration preventing agent, anti-glaucoma agent, immune response modifier, peptide, protein, steroid, corticosteroid, antibacterial agent, neuroprotective agent, anti-inflammatory agent, antiallergic agent, anticholinesterase, mydriatic agent, and mydriatic agent.

16. The method of treating a patient according to any one of claims 12 to 15, wherein the bioerodible outer member is tubular.

17. The method of treating a patient of claim 16, wherein each end of the tubular bioerodible outer member includes a delivery port.

18. The method of treating a patient according to claim 12, wherein the predetermined treatment period is in the range of 1 day to 30 days.

19. The method of treating a patient according to claim 12, wherein the predetermined treatment period is in the range of 1 day to 180 days.

20. The method of treating a patient according to claim 12, wherein the predetermined treatment period is in the range of six months to one year.

21. The method of treating a patient according to claim 12, wherein the predetermined treatment period is in the range of one year to three years.

22. The method of treating a patient according to claim 12, wherein the pharmaceutically active agent is a corticosteroid.

23. A method of manufacturing an implantable bioerodible drug delivery device, the method comprising

Combining a pharmaceutically active agent with a solution comprising a first bioerodible polymer to form a particulate composition;

extruding the particulate composition;

coating the extruded particulate composition with a second bioerodible polymer, wherein the second bioerodible polymer is impermeable to the pharmaceutically active agent after implantation of the device;

drying the coated extruded particulate composition;

applying a third bioerodible polymer to form one or more delivery ports, wherein the one or more delivery ports are permeable to the pharmaceutically active agent after implantation of the device.

24. The method of manufacturing according to claim 23, wherein the pharmaceutically active agent is selected from the group consisting of: anesthetic, anticancer agent, antifungal agent, antiviral agent, cell transport/migration preventing agent, anti-glaucoma agent, immune response modifier, peptide, protein, steroid, corticosteroid, antibacterial agent, neuroprotective agent, anti-inflammatory agent, antiallergic agent, anticholinesterase, mydriatic agent, and mydriatic agent.

25. The method of claim 23, wherein the implantable bioerodible drug delivery device is tubular.

26. The method of claim 25, wherein each end of the tubular implantable bioerodible drug delivery device comprises a delivery port.

27. The method of claim 25, wherein one end of the tubular implantable bioerodible drug delivery device is sealed with a polymer impermeable to the pharmaceutically active agent after implantation of the device and the other end comprises a delivery port.

28. The method of any one of claims 23 to 27, wherein the second bioerodible polymer comprises a polymer selected from the group consisting of: lactic-glycolic acid copolymers, polycaprolactone, polylactic acid, polyglycolic acid and polyvinyl alcohol and mixtures thereof.

Technical Field

The present invention relates to implantable bioerodible drug delivery devices for delivering a wide variety of pharmaceutically active agents. The invention also relates to methods of using such devices to treat patients in need of therapeutic relief, and methods of making such devices.

Background

Implantable drug delivery devices have certain advantages over conventional methods of administration, such as oral administration or injection. For example, in conventional methods of administration, the concentration of the drug may vary significantly, i.e., reach a maximum concentration (C) shortly after administration_{Maximum of}) And then drops sharply. In order to maintain therapeutic levels, it may also be necessary to administer drugs at such doses, although high doses may temporarily result in high concentrations that are actually toxic to the patient. Subsequently, the drug concentration may be reduced to safe therapeutic levels as the drug is metabolized or cleared in the body. When the drug level drops to a sub-therapeutic level, a subsequent dose may be administered and the cycle repeated accordingly. Thus, a problem with conventional administration is that for certain types of drugs, patients may be exposed to undesirably high levels of the drug for extended periods of time in the repeated cycles of administration required for treatment.

Implantable drug delivery devices can avoid many of these problems because implantation at or near the area requiring treatment reduces the need for high systemic concentrations of the drug for the purpose of achieving a therapeutic effect. However, achieving a constant dosing rate (so-called zero order release) can be challenging. In many systems, the release rate is time dependent and the amount of drug released is proportional to the square root of time (or Fickian). For example, implantable devices containing a drug dispersed within a matrix often do not exhibit zero order release. While drugs near the outer surface of the matrix may be released relatively easily, drugs located deep within the core of the device must diffuse through the depleted matrix for release. The net result is that the release rate is slow and Fickian release is trivial. For matrix systems, zero order release is difficult to achieve. The same principle applies to release in a gel.

Another problem with many implantable drug delivery devices is that the devices may be constructed of non-biodegradable materials that remain permanently within the patient's body even after all of the drug has been administered. This can be problematic in many different situations. For example, when implanting an implantable drug delivery device into an anatomical location having a small volume, the number of therapeutic treatments available through the implant for the patient may be limited due to an undesirable accumulation of non-biodegradable portions of the implantable drug delivery device. This is particularly true where the implantable drug delivery device is implanted in the eye to treat an ocular disease or disorder. Any non-biodegradable part of the device that would remain permanently in the eye risks interfering with the patient's vision. As another example, when an implantable drug delivery device is implanted into a joint to treat musculoskeletal disorders, the non-biodegradable portion of the device that remains in the joint may interfere with the full mobility of the joint.

In view of all of the above, there remains a need in the art for improved device designs and methods of making such devices that provide controlled and sustained release of a drug to a patient to achieve a desired local or systemic physiological or pharmacological effect.

Disclosure of Invention

In one aspect, the present invention provides an implantable bioerodible drug delivery device that includes a drug core comprising a pharmaceutically active agent. The device also has a bioerodible outer member comprising a first bioerodible polymer substantially surrounding the drug core. The first bioerodible polymer is impermeable to the pharmaceutically active agent after implantation of the device. The bioerodible outer member also has at least one delivery port comprising a second bioerodible polymer that is permeable to the pharmaceutically active agent after implantation of the device. The bioerodible outer member is configured to provide a substantially constant dosing rate of the pharmaceutically active agent over a predetermined treatment period after implantation.

In another aspect, the invention provides a method of treating a patient. The method comprises the following steps: identifying a region of a patient in need of treatment; and implanting a bioerodible drug delivery device sufficiently close to the area in need of treatment to provide therapeutic relief. The bioerodible drug delivery device includes a drug core comprising a pharmaceutically active agent. The bioerodible drug delivery device also has a bioerodible outer member that substantially surrounds the drug core and is impermeable to the pharmaceutically active agent after implantation of the device. The bioerodible outer member also has at least one delivery port comprising a second bioerodible polymer that is permeable to the pharmaceutically active agent after implantation of the device. The bioerodible outer member is configured to provide a substantially constant dosing rate of the pharmaceutically active agent over a predetermined treatment period after implantation.

In another aspect, the present invention provides a method of manufacturing an implantable bioerodible drug delivery device. The method comprises the following steps: the pharmaceutically active agent is combined with a solution comprising a first bioerodible polymer to form a particulate composition. Extruding the particulate composition and then coating the particulate composition with a second bioerodible polymer that is impermeable to the pharmaceutically active agent when the device is implanted. The coated extruded particulate composition is then dried and a third bioerodible polymer is applied to form one or more delivery ports. These delivery ports are permeable to the pharmaceutically active agent after implantation of the device.

Drawings

FIG. 1: an exemplary implantable bioerodible drug delivery device according to one embodiment of the invention wherein the outer member comprises a single polymeric layer.

FIG. 2: an exemplary implantable bioerodible drug delivery device according to one embodiment of the invention wherein the outer member comprises two distinct polymeric layers.

FIG. 3: (a) an exemplary implantable bioerodible drug delivery device according to one embodiment of the invention, wherein one end of the device is sealed with a polymer that is impermeable to the pharmaceutically active agent in the drug core; (b) an exemplary implantable bioerodible drug delivery device according to one embodiment of the invention, wherein each end of the device comprises a delivery port comprising a polymer layer that is permeable to a pharmaceutically active agent contained in a drug core.

FIG. 4: (a) an exemplary implantable bioerodible drug delivery device according to one embodiment of the invention, wherein the bioerodible outer member comprises two polymer layers, and wherein one end of the device is sealed with a polymer that is impermeable to the pharmaceutically active agent in the drug core; (b) an exemplary implantable bioerodible drug delivery device according to one embodiment of the invention wherein the bioerodible outer member comprises two polymer layers and each end of the device comprises a delivery port comprising a polymer layer that is permeable to the pharmaceutically active agent contained in the drug core.

FIG. 5: an exemplary implantable drug delivery device according to one embodiment of the present invention, wherein the outer member includes two polymer layers, and the outermost polymer layer of the outer member also forms a portion of the delivery port.

FIG. 6: an exemplary implantable drug delivery device according to one embodiment of the present invention, wherein the outer member includes a plurality of delivery ports.

FIG. 7: a graph illustrating the release characteristics of a device according to an embodiment of the present invention.

FIG. 8: a graph illustrating the release characteristics of a device according to an embodiment of the present invention.

Detailed Description

In one aspect, the present invention provides an implantable bioerodible drug delivery device adapted to release a pharmaceutically active agent in a controlled and sustained manner to a patient in need thereof in order to obtain local or systemic therapeutic relief. As used herein, the terms "bioerodible" (and variations thereof) and "biodegradable" (and variations thereof) refer to the ability of a polymer or device to chemically break down (e.g., via a hydrolysis reaction) or dissolve, as the case may be, after the polymer or device has been implanted in the body. One advantage of the present invention is that the drug delivery device does not need to be removed after administration of the pharmaceutically active agent is complete. Rather, the drug delivery device may be left in the body, where it slowly biodegrades over time to form harmless byproducts that are cleared by normal metabolic processes. Another advantage of the present invention is that a drug delivery device can be used to deliver a pharmaceutically active agent at a constant rate over a predetermined period of time.

In general, the implantable bioerodible drug delivery device of the invention includes at least one drug core comprising one or more pharmaceutically active agents. In many embodiments of the invention, the implantable bioerodible drug delivery device of the invention comprises exactly one drug core, but the invention expressly encompasses devices having two or more drug cores that may comprise the same or different pharmaceutically active agents. In certain embodiments, the drug core comprises a pharmaceutically active agent without any other additives. Typically, this type of core is used where the pharmaceutically active agent has a relatively low solubility in the body. However, if desired, the pharmaceutically active agent may be combined with a bioerodible polymer that acts as a bulking agent and/or controls the rate at which the pharmaceutically active agent will dissolve in vivo. In general, the bioerodible polymer selected will be chemically inert with respect to the pharmaceutically active agent during manufacture of the sustained release device, during subsequent storage, and after the sustained release device has been implanted into the area of the patient in need of treatment. Non-limiting examples of bioerodible polymers contemplated by the present invention include polyvinyl alcohol (PVA) and poly (lactic-co-glycolic acid) (PLGA). In preferred embodiments, the bioerodible polymer comprises about 1% to about 5%, about 1% to about 10%, about 1% to about 20%, about 1% to about 25%, about 1% to about 30%, about 1% to about 35%, about 1% to 40%, about 1% to about 45%, or about 1% to about 50% of the drug core by weight.

In certain embodiments, the drug core may be formed by: one or more pharmaceutically active agents in powder form are combined with a solution having a bioerodible polymer dissolved therein and mixed until the composition has a consistency of granules and/or paste. Such compositions may be further processed, if desired, by extruding the composition through a die. In certain embodiments, the extrudate has a generally cylindrical shape, although other shapes (e.g., cubes, discs, etc.) are expressly contemplated by the present invention. After extrusion, the extrudate is advantageously dried to remove the solvent of the bioerodible polymer solution. In certain embodiments, the extrudate is air dried at room temperature, but the present invention also specifically contemplates drying at elevated temperatures, preferably at temperatures that do not affect the stability of the one or more pharmaceutically active agents or any bioerodible polymer that has been added to the core.

The pharmaceutically active agents encompassed by the present invention are not particularly limited and may include any pharmaceutically active agent that is sufficiently stable under the conditions of manufacture and storage and that is compatible with the materials used to fabricate the implantable bioerodible drug delivery device.

The following exemplary classes of agents may be incorporated into the devices of the present invention: anesthetics and analgesics such as lidocaine and related compounds and benzodiazepines and related compounds; anti-cancer agents such as 5-fluorouracil, doxorubicin and related compounds; antifungal agents, such as fluconazole and related compounds; antiviral agents such as trisodium phosphine-formate, trifluorothymidine, acyclovir, ganciclovir, DDI, DDC and AZT; cell transport/migration preventing agents such as colchicine, vincristine, cytochalasin B and related compounds; anti-glaucoma agents, such as beta-blockers: timolol, betaxolol, atenolol, and the like; immune response modifiers, such as muramyl dipeptide and related compounds; peptides and proteins such as cyclosporine, insulin, growth hormone, insulin-related growth factor, heat shock proteins and related compounds, and carbonic anhydrase inhibitors.

In certain embodiments, the pharmaceutically active agent is an anti-inflammatory agent. For example, the pharmaceutically active agent may be a steroid or corticosteroid, non-limiting examples of which include fluocinolone, hydrocortisone acetate, triamcinolone acetonide, methylprednisolone, dexamethasone, medrysone, methylprednisolone, prednisolone 21-phosphate, prednisolone acetate, fluorometholone, and betamethasone. The present invention also encompasses the use of non-steroidal anti-inflammatory drugs (NSAIDs). Non-limiting examples of NSAIDs include diclofenac, etodolac (etodolac), fenoprofen, flurbiprofen, ibuprofen, indoprofen, ketoprofen, ketorolac, lornoxicam, molelazone, naproxen, perisoxazole, pirprofen, pranoprofen, suprofen, succinoden, tropin (tropisin), jomoprofen, zaltoprofen, zileuton, and zomepirac. NSAIDs encompassed by the present invention also include COX-2 inhibitors, examples of which include valdecoxib, rofecoxib, and celecoxib. In addition to the aforementioned anti-inflammatory agents, the present invention also specifically encompasses the use of analogs, derivatives, pharmaceutically acceptable salts, esters, prodrugs, co-drugs, and protected forms thereof.

In addition to the above agents, other agents include neuroprotective agents such as nimodipine and related compounds; tyrosine kinase inhibitors such as bosutinib and dasatinib, antibiotics such as tetracycline, aureomycin, bacitracin, neomycin, polymyxin (polyrnyxin), gramicidin, oxytetracycline, chloramphenicol, gentamicin, and erythromycin; antibacterial agents such as sulfonamides, sulfacetamide, sulfamethoxazole, sulfisoxazole, nitrofurazone, and sodium propionate; antiviral agents, including idoxuridine; antiallergic agents such as antazoline, methamphetamine, chlorpheniramine, mepyramine and amiton; fibrinolytic agents (e.g., tissue plasminogen activator, streptokinase, and urokinase); decongestants such as phenylephrine, naphazoline, and tetrahydrozoline; mydriatics and anticholinesterases such as pilocarpine, physostigmine salicylate, carbachol, diisopropyl fluorophosphate, phosphorylcholine iodide and dimehypo bromide; mydriatics such as atropine sulfate, cyclopentadine, homatropine, scopolamine, tropicamide, eucalyptol and hydroxylamphetamine; sympathomimetic agents, such as epinephrine; and prodrugs such as those described in Design of produgs, edited by hans bundgaard, Elsevier Scientific Publishing co., Amsterdam, 1985. Again, reference may be made to any standard Pharmaceutical textbook, such as Remington's Pharmaceutical Sciences, to identify additional agents.

In certain embodiments, the pharmaceutically active agent is an antibiotic. In some embodiments, the antibiotic may be administered as the sole pharmaceutically active agent in the implantable bioerodible drug delivery device according to the invention. However, in other embodiments, the antibiotic is co-administered with another pharmaceutically active agent. For example, where an implantable bioerodible drug delivery device comprising an anti-inflammatory drug is surgically implanted to treat musculoskeletal disorders, antibiotics may be co-administered to reduce the likelihood of infection at the surgical wound. Administration of antibiotics in such cases may utilize separate sustained delivery devices that are co-implanted. Alternatively, antibiotics may be combined with anti-inflammatory drugs such that they are part of the same drug core. The type of antibiotic is not particularly limited and can be any antibiotic having the desired chemical stability to withstand the manufacturing process and subsequent storage conditions prior to use. Non-limiting examples of antibiotic compounds encompassed by the present invention include aminoglycosides (e.g., amikacin, gentamicin, kanamycin, neomycin, netilmicin, tobramycin, paromomycin, streptomycin, spectinomycin), carbapenems (e.g., meropenem, imipenem, doripenem), cephalosporins (e.g., cefixime, cefdinir, cefditoren, cefoperazone, cefotaxime, cefepime), glycopeptides (teicoplanin, vancomycin, telavancin, dalbavancin), lincosamides (clindamycin, lincomycin), and macrolides (e.g., azithromycin, erythromycin).

In addition to the drug core, the implantable drug delivery device according to the present invention includes a bioerodible outer member that houses the drug core. Typically, the bioerodible outer member comprises one or more bioerodible polymers that substantially cover or coat the drug core and that have a suitable composition and sufficient thickness to retain their shape during a predetermined treatment period and remain impermeable to the pharmaceutically active agent in the drug core. In general, the bioerodible polymer used to make the bioerodible outer member is not limited and can be any bioerodible polymer having the desired biocompatibility for use as an implant and impermeability during a predetermined treatment period. Non-limiting examples of bioerodible polymers suitable for implantable drug delivery devices of the present invention include lactic acid-glycolic acid copolymer, polylactic acid, polyglycolic acid, and polyvinyl alcohol, and mixtures thereof. For a given implantable drug delivery device, the bioerodible polymer and the desired predetermined treatment period, appropriate thickness to render the bioerodible shell impermeable, can be determined by diffusion cell studies performed under sink conditions as described herein. Useful wall thicknesses for the bioerodible shell can be, for example, in the range of about 40 μm to about 120 μm. In certain preferred embodiments, the bioerodible shell has a wall thickness of at least about 40 μm, but less than or equal to about 100100 μm.

The implantable drug delivery device of the present invention may be equipped with one or more delivery ports to permit delivery of the pharmaceutically active agent in the drug core. It will be appreciated that the size of the one or more delivery ports will control the rate of administration, with larger delivery ports leading to a greater degree of dissolution per unit time and hence a faster rate of administration. In certain implementations of the invention, the delivery port may simply be a void in the bioerodible outer member that permits the drug core to directly contact the patient's bodily fluids after implantation. In such implementations, direct contact between the drug core and body fluids can over time cause the pharmaceutically active agent of the drug core to dissolve and be released into the body fluids and surrounding tissues. This type of delivery port is particularly suitable where the drug core has low solubility in body fluids that contact the drug core after implantation. In such implementations, the size of the one or more pores preferably remains substantially unchanged during the predetermined treatment period so as to facilitate a substantially constant dosing rate. Further, the delivery port may be made by: pores are created in the bioerodible outer member and covered with a permeable bioerodible polymer. In such cases, the permeable bioerodible polymer may be used to modulate the diffusion rate of the pharmaceutically active agent of the drug core in the surrounding tissue after implantation. This may be achieved, for example, by selecting a permeable bioerodible polymer that has a permeability with a sufficiently slow degradation rate in vivo that is substantially unchanged during a predetermined treatment period. In this way, one can achieve a constant dosing rate (zero order release kinetics) over a predetermined treatment period, provided that the concentration of dissolved drug in the device remains constant over the predetermined treatment period. In certain preferred embodiments, the bioerodible polymer layer on the delivery port has a varying thickness, which can be adjusted by using different concentrations of bioerodible polymer solution (0.05% to 10%) or by the timing of the applied solution coating.

In a preferred embodiment, the implantable bioerodible drug delivery device of the invention releases the pharmaceutically active agent at a substantially constant rate (i.e., zero order drug release kinetics) over a predetermined time period following the initial transient period following implantation. It will be appreciated that in a preferred embodiment of the invention, the initial transient period is much less than the predetermined time period (e.g. less than 10%). Without wishing to be bound by theory, it is believed that the non-zero order release kinetics during the initial transient period are caused by changes (e.g., infiltration or diffusion phenomena) that occur as the implantable bioerodible drug delivery device gradually reaches steady state after implantation. Diffusion cell studies can be conducted under sink conditions to determine the rate at which a particular pharmaceutically active agent is released through a given permeable bioerodible polymer layer. In general, such studies involve monitoring the diffusion of a pharmaceutically active agent between two compartments: a donor region and a acceptor region. The concentration of the drug in the receptor zone is substantially zero when compared to the high concentration in the donor zone. Under these conditions, the drug release rate is given by:

where Q is the amount of pharmaceutically active agent released, t is time, D is the diffusion coefficient, K is the partition coefficient, a is the surface area, DC is the difference in concentration of the pharmaceutically active agent across the permeable bioerodible polymer layer, and h is the thickness of the permeable bioerodible polymer layer.

Under sink conditions, the value DC is substantially constant and equal to the concentration of the donor region if the release from the donor side is very slow. The release rate thus becomes dependent on the surface area (a), thickness (h) and diffusivity (D) of the bioerodible polymer layer. In the construction of the device of the present invention, the size (and thus the surface area) is primarily dependent on the size of the pharmaceutically active agent. Thus, the permeability of a given bioerodible polymer layer of interest can be obtained from the slope of the Q versus time plot. The permeability P can be related to the diffusion coefficient D by the following formula:

once the permeability rate is established for the permeable bioerodible polymer layer of interest relative to diffusion of the pharmaceutically active agent therein, appropriate device dimensions can be determined to achieve the desired administration and administration rate. As taught herein, device dimensions such as diameter and length can be adjusted along with diffusion port surface area to tailor the release rate and amount of the pharmaceutically active agent. It will be appreciated that in the implantable drug delivery device of the present invention comprising a permeable bioerodible polymer layer over the delivery pores, the pharmaceutically active agent diffuses in the direction of the lower chemical potential, i.e., towards the outer surface of the device. At the outer surface of the device, equilibrium is again established. When equilibrium is reached on both sides of the permeable bioerodible polymer layer of the delivery pore, the steady state flux of the effective agent will be established according to Fick's law of diffusion. Under such conditions, the drug concentration on both sides of the permeable bioerodible polymer layer remains unchanged with respect to time, but is clearly different. The rate of passage of a pharmaceutically active agent by diffusion through a permeable bioerodible polymer layer generally depends on the solubility of the drug therein and on the thickness of the layer. Thus, selection of appropriate materials and dimensions for the device (such as, but not limited to, thickness of the bioerodible polymer, inner diameter of the device, thickness of the polymer coating the end of the device, size of the delivery port) and active ingredient formulation all work synergistically together to achieve a desired release rate of the active agent and ensure that all or substantially all of the active agent has been delivered to the patient from the delivery port before the bioerodible polymer degrades to a level that exposes the drug core. Thus, the materials and device dimensions, as well as the active agent, are carefully selected to fabricate the device to achieve the intended and desired predetermined treatment period. Thus, for example, an implantable device may be designed to deliver pain control drugs at high doses over a short period of time (e.g., two weeks) to bring therapeutic relief, while the same size implantable device may be used to deliver anti-inflammatory drugs at much lower doses over six months.

The bioerodible outer member can be fabricated using different techniques in accordance with the invention. For example, in certain embodiments, the bioerodible outer member can be formed by dip coating the drug core of the invention in a solution comprising a bioerodible polymer, non-limiting examples of which include lactic-glycolic acid copolymer, polylactic acid, polyglycolic acid, polycaprolactone, and polyvinyl alcohol, and mixtures thereof. Non-limiting examples of suitable solutions include those comprising about 1% to about 20%, about 2% to about 18%, about 5% to about 15%, about 8% to about 12%, or about 10% w/w of the bioerodible polymer. If desired, the core may be dipped multiple times into the bioerodible polymer solution to increase the thickness of the bioerodible outer member. For example, a bioerodible outer member having a desired thickness can be formed by immersing the core in a solution comprising a bioerodible polymer and air drying a repeated cycle of the polymer coating around the core. In some embodiments, two or more different types of bioerodible polymers can be co-dissolved in the dip coating solution. In the alternative, the present invention also encompasses a continuous dip coating process, wherein the core is immersed in different polymer solutions. In such embodiments, the core may be dipped into each type of polymer solution one or more times as needed to achieve the desired coating for a given application.

When dip coating the core to form the impermeable bioerodible outer member, it is often the case that the entire core is completely covered by the impermeable bioerodible polymer coating. To form a delivery port in such cases, it is advantageous to create a corresponding opening in the impermeable bioerodible polymer layer for delivery of the pharmaceutically active agent. If desired, one can use mechanical means to create the delivery port, including piercing, grinding, or cutting the impermeable bioerodible polymer layer. In one non-limiting embodiment, a cylindrical core formed by extrusion and dip-coated with an impermeable bioerodible polymer layer is transversely cut to create a delivery port that is a cross-section of the exposed core. If desired, the exposed core may be coated with a bioerodible polymer that is permeable to the pharmaceutically active agent after implantation of the device to control the rate of delivery of the pharmaceutically active agent. While the foregoing description relates to a cylindrical implantable bioerodible drug delivery device having one delivery port, it is to be understood that the invention also specifically encompasses devices having two or more delivery ports. For example, a cylindrical core formed by extrusion and dip-coated with an impermeable bioerodible polymer layer can be transversely cut at both ends to form two delivery ports, which optionally can be coated with a permeable bioerodible polymer. If desired, the extruded core may be heat treated prior to dip coating, between dip coating steps, or after dip coating is completed to drive off any solvents that may have been used in the manufacturing process. Generally, the heat treatment is performed at a temperature that can safely drive off the solvent without causing undesirable degradation of the pharmaceutically active agent or undesirable side reactions. In addition, a heat treatment step may be performed to alter the permeability or in vivo degradation rate of the bioerodible polymer used to fabricate the implantable drug delivery device of the invention. For example, when the implantable drug delivery device of the present invention comprises a polyvinyl alcohol layer, the permeability and water solubility of the polyvinyl alcohol layer may be reduced by heat treatment.

In other embodiments, the bioerodible outer member is a rigid article into which the drug core is inserted or deposited during manufacture. For example, the bioerodible outer member can be a hollow rigid tubular member into which the drug core is inserted or extruded. In one non-limiting embodiment, the drug core is initially a composition having a viscosity sufficiently low such that the composition can be inserted or extruded into a rigid tubular bioerodible outer member by a plunger, push rod, or the like. In some cases, the pharmaceutically active agent may be combined with a solvent (and optionally a bioerodible polymer) such that the viscosity of the initial drug core composition is sufficiently low that the composition can be poured, injected, or sucked into a tube by vacuum. In such cases, it may be advantageous to heat the device to drive off substantially all of the residual solvent prior to implantation.

In certain preferred embodiments, the outer diameter of the tubular bioerodible outer member is selected such that the implantable drug delivery device of the invention can be implanted into a patient's eye using a needle having a gauge of 25 or larger (a smaller needle). One aspect of the present invention recognizes that when such a needle is used to inject an implantable drug delivery device into a patient's eye, the wall of the tubular bioerodible outer member must be thick enough to maintain both the structural integrity of the implantable drug delivery device during implantation and the desired zero order release kinetics over a predetermined treatment period. Thus, for example, when the tubular bioerodible outer member of such an implantable drug delivery device is manufactured using poly (lactic-co-glycolic acid) (PLGA), useful wall thicknesses fall within the range of 40 to 80 μm. By using a wall thickness in this range, the tubular PLGA bioerodible outer member causes the implantable bioerodible drug delivery device to exhibit substantially zero order release kinetics after implantation into the eye, but the tubular PLGA bioerodible member will still fully degrade over a time scale approximating the predetermined treatment period. In this way, implantable drug delivery devices of this type may be sequentially implanted into a patient's eye without more than one used device remaining in the eye for a predetermined treatment period.

In general, the shape of the implantable bioerodible drug delivery device is preferably cylindrical for ease of manufacture. However, other shapes are also explicitly contemplated, and regular shapes (e.g., cubes, discs, etc.) are particularly preferred. Where the bioerodible drug delivery device is cylindrical, the cross-section of such devices (not shown) tends to appear circular. While it is preferred to manufacture implantable bioerodible drug delivery devices as cylinders having circular cross-sections, it is within the scope of the invention to manufacture such devices as cylinders having cross-sections of different shapes, such as: oval, elliptical, rectangular (including square), triangular, and any other regular polygonal or irregular shape.

Turning now to the drawings, fig. 1 shows a longitudinal cross-sectional view of an implantable drug delivery device 100 according to one implementation of the present invention. The device 100 includes a drug core 105, the drug core 105 comprising one or more pharmaceutically active agents. One or more pharmaceutically active agents optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the rate of dissolution of the core in vivo. The device 100 further includes a bioerodible outer member 110, the bioerodible outer member 110 fabricated using a bioerodible polymer to create a shell that is substantially impermeable to the pharmaceutically active agent contained in the drug core 105 after implantation, at least during a predetermined treatment period. The device 100 also features two delivery ports 115, the two delivery ports 115 being located at opposite ends of the device 100. In this particular embodiment, delivery port 115 directly exposes drug core 105 to the surrounding environment, and it is expected that the pharmaceutically active agent contained in drug core 105 will be released from delivery port 115 as drug core 105 is dissolved by body fluids after implantation of device 100.

Fig. 2 illustrates a longitudinal cross-sectional view of an implantable drug delivery device 200 according to another implementation of the present invention. In fig. 2, the device 200 includes a drug core 205, the drug core 205 comprising one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the dissolution rate of the drug core in vivo. The device 200 also includes a bioerodible outer member 210, the bioerodible outer member 210 being a multi-layer structure comprised of a first bioerodible polymer layer 212 and a second bioerodible polymer layer 220. Although only two polymer layers 212, 220 are shown in fig. 2, it is to be understood that the present invention encompasses devices in which the bioerodible outer member includes three or more bioerodible polymer layers. Additionally, it should be noted that each polymer layer of the bioerodible outer member 110, 210 can independently comprise a copolymer (e.g., a block copolymer, an alternating copolymer, or a random copolymer). Drug delivery device 200 also includes two delivery ports 215, the two delivery ports 215 being located at opposite ends of device 200. As in the case of fig. 1, the delivery port 215 in fig. 2 directly exposes the drug core 205 to the ambient environment. As the drug core 205 is dissolved by body fluids after implantation of the device 200, the pharmaceutically active agent contained in the drug core 205 will be released from the delivery port 215.

Fig. 3(a) shows a longitudinal cross-sectional view of an implantable drug delivery device 301 according to another implementation of the present invention. The device 301 includes a drug core 305, the drug core 305 comprising one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the dissolution rate of the drug core in vivo. The device 301 also includes a bioerodible outer member 310 fabricated using a bioerodible polymer to create a shell that substantially covers the pharmaceutically active agent contained in the drug core 305. The bioerodible polymer is substantially impermeable to the pharmaceutically active agent contained in the drug core 305 for at least the predetermined treatment period. The device 301 features a delivery port 360, the delivery port 360 directly exposing the drug core 305 to the ambient environment. As the drug core 305 is dissolved by body fluids after implantation of the device 301, the pharmaceutically active agent contained in the drug core 305 will be released from the delivery port 360. At the other end of the device 301, a bioerodible polymeric cap 350 that is impermeable to the pharmaceutically active agent in the drug core 305 prevents the administration of such agents from the end of the device where the bioerodible polymeric cap 350 is located. While fig. 3(a) shows that the bioerodible polymeric cap 350 will be composed of a different polymer than the bioerodible outer member 310, it is to be understood that the bioerodible outer member and the bioerodible polymeric cap can be fabricated together as a single integral unit, if desired. Fig. 3(b) shows a longitudinal cross-sectional view of an implantable drug delivery device 302 according to another implementation of the present invention. In fig. 3(b), the device 302 includes a drug core 305, the drug core 305 including one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the dissolution rate of the drug core in vivo. The device 302 also includes a bioerodible outer member 310 that is fabricated using a bioerodible polymer to create a shell that substantially covers the pharmaceutically active agent contained in the drug core 305. The bioerodible polymer is substantially impermeable to the pharmaceutically active agent contained in the drug core 305 for at least the predetermined treatment period. The device 302 features two delivery ports with permeable bioerodible polymer layer 350 that permit diffusion therethrough of the pharmaceutically active agent contained in the drug core 305.

Figure 4 shows an additional embodiment of the present invention. Fig. 4(a) provides a longitudinal cross-sectional view of an implantable drug delivery device 401. The device 401 includes a drug core 405, the drug core 405 including one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the dissolution rate of the drug core in vivo. The device 401 further includes a bioerodible outer member 410, the bioerodible outer member 410 being a multilayer structure comprised of a first bioerodible polymer layer 412 and a second bioerodible polymer layer 420. Similar to the embodiment shown in fig. 2, the device 401 is not limited to a bioerodible outer member 410 having only two polymer layers 412, 420. Rather, it is understood that three or more bioerodible polymer layers can be used to form the bioerodible outer member 410. Additionally, it should be noted that each polymer layer of the bioerodible outer member 410 can include a copolymer (e.g., a block copolymer, an alternating copolymer, or a random copolymer). Drug delivery device 401 also includes a single delivery port 460 that directly exposes drug core 405 to the surrounding environment through delivery port 460. After implantation, the drug core 405 will gradually be dissolved by the body fluids and the pharmaceutically active agent contained in the drug core 405 will be released from the delivery port 460. A bioerodible polymeric cap 450 comprised of a polymer that is impermeable to the pharmaceutically active agent of the drug core 405 during a predetermined treatment period prevents release of the pharmaceutically active agent from the end of the device 401 opposite the delivery port 460. As in the case of fig. 3(a), it is understood that the bioerodible outer member and the bioerodible polymeric cover can be fabricated together as a unitary structure comprising the same material.

Fig. 4(b) provides a longitudinal cross-sectional view of the implantable drug delivery device 402. As in the case of the device 401 in fig. 4(a), the device 402 in fig. 4(b) includes a drug core 405, the drug core 405 including one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the rate of dissolution of the drug core in vivo. The device 402 also includes a bioerodible outer member 410, the bioerodible outer member 410 being a multilayer structure comprised of a first bioerodible polymer layer 412 and a second bioerodible polymer layer 420. Additional bioerodible polymer layers can be included if desired, depending on the desired application and/or the intended treatment period. Drug delivery device 402 also includes two delivery ports that include permeable bioerodible polymer layer 450. After implantation, the patient's body fluids penetrate the bioerodible polymer layer 450 to dissolve the drug core 405, thereby releasing the pharmaceutically active agent contained therein.

Fig. 5 provides a longitudinal cross-sectional view of an implantable drug delivery device 500 according to another embodiment of the present invention. The device 500 includes a drug core 505, the drug core 505 comprising one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the dissolution rate of the drug core in vivo. The device 500 further includes a bioerodible outer member 510, the bioerodible outer member 510 being fabricated using a bioerodible polymer that is impermeable to the pharmaceutically active agent contained in the drug core 505 at least during a predetermined treatment period. Encapsulating the entire device is a bioerodible polymer layer 520, the bioerodible polymer layer 520 being permeable to the pharmaceutically active agent contained in the drug core 505. After implantation, the drug core 505 is gradually dissolved by body fluids and the pharmaceutically active agent contained in the drug core 505 diffuses through the end region 550.

Fig. 6 provides a top view and a longitudinal cross-sectional view of an implantable drug delivery device 600 according to another embodiment of the present invention. In fig. 6, a drug delivery device 600 includes a drug core 605, the drug core 605 including one or more pharmaceutically active agents, which optionally may be mixed with at least one bioerodible polymer that acts as a bulking agent and/or controls the dissolution rate of the drug core in vivo. The device 600 further includes a bioerodible outer member 620, the bioerodible outer member 620 fabricated using a bioerodible polymer to create a shell that substantially covers the pharmaceutically active agent contained in the drug core 605. The bioerodible polymer is impermeable to the pharmaceutically active agent in the drug core 605 at least during the predetermined treatment period. As shown in fig. 6, device 600 features two delivery ports (650a, 650b) at respective ends of the device, and additional delivery ports (650c, 650d, and 650e) disposed along the length of device 600. It is contemplated that the pharmaceutically active agent contained in drug core 605 will be released from delivery ports 650a-650e as drug core 605 is dissolved by body fluids after implantation of device 600. Thus, the presence of an additional delivery port is particularly useful when more rapid delivery of the pharmaceutically active agent is desired after implantation of the device 600. In certain embodiments, it may be advantageous to have additional delivery ports 650c, 650d, and 650e located on the same side of device 600 for ease of manufacturing and handling. For example, additional delivery ports 650c, 650d, and 650e may be arranged co-linearly in a longitudinal direction along one side of device 600. This configuration is advantageous because it permits the device 600 to be anchored or attached to a body part via the longitudinal sides of the device opposite the longitudinal sides of the additional delivery ports 650c, 650d and 650e without affecting the drug administration rate. In other embodiments, the additional delivery ports 650c, 650d, and 650e are not on the same side of the device 600, which may result in a more spatially isotropic dosing profile. However, it should be understood that the number of delivery ports, the shape of the delivery ports, and the particular location of the delivery ports in fig. 6 are merely illustrative and are not intended to limit the present invention in any way. In a preferred embodiment and as shown in fig. 6, the delivery port includes a permeable bioerodible polymer layer through which the pharmaceutically active agent must diffuse after implantation in order to provide therapeutic relief. If desired, the permeability of such layers is selected such that diffusion of the pharmaceutically active agent through the layers is rate-limiting.

The invention further relates to a method of treating a mammalian organism to obtain a desired local or systemic physiological or pharmacological effect. The method comprises the following steps: administering an implantable bioerodible drug delivery device to a mammalian organism; and allowing diffusion of the pharmaceutically active agent from the device to produce a desired local or systemic effect. The term administering as used herein means positioning, inserting, injecting, implanting, anchoring, attaching or any other means for exposing the device to a mammalian organism, preferably a human. The route of administration depends on various factors including the type of response or treatment, the type of agent, and the preferred site of administration.

The devices are, in certain embodiments, adapted to provide controlled and sustained release of an agent effective to achieve at least a desired local or systemic physiological or pharmacological effect associated with the following fields: treating cancerous primary tumors (e.g., glioblastoma); inhibiting neovascularization, including ocular neovascularization; edema, including ocular edema; inflammation, including ocular inflammation; hormone deficiency, such as diabetes; musculoskeletal disorders, such as chronic pain; arthritis; rheumatism; and dwarfism; and modulating immune responses, such as in the prevention of transplant rejection and in the treatment of cancer. Many other disease states may also be prevented or treated using the drug delivery devices of the present invention. Such disease states are known to those of ordinary skill in the art. For persons not skilled in the art, reference may be made to: goodman and Gilman, the pharmacological Basis of Therapeutics, 8 th edition, Pergamon Press, N.Y., 1990; and Remington's Pharmaceutical Sciences, 18 th edition, Mack Publishing co., Easton, Pa., 1990; both of which are incorporated herein by reference.

The implantable bioerodible drug delivery device of the invention is particularly suitable for treating ocular diseases such as glaucoma, proliferative vitreoretinopathy, macular edema including diabetic macular edema, age-related macular degeneration, diabetic retinopathy, uveitis, ocular neovascularization, retinal vein occlusion, geographic atrophy, and ocular infections. The device is also particularly suitable for use as an ophthalmic device in the treatment of mammalian organisms (both for human and veterinary use) suffering from ocular histoplasmosis, wherein the device is surgically implanted into the vitreous of the eye.

In general, the implantable bioerodible drug delivery device of the invention is designed to provide a substantially zero-order release of one or more pharmaceutically active agents over a predetermined treatment period. The predetermined treatment period will vary depending on the disease or condition to be treated, the severity of the condition, and the duration of symptom relief desired. For example, in certain embodiments, the predetermined period lasts at least one month, two months, three months, four months, five months, six months, or 12 months, and is less than or equal to 48 months, 40 months, 36 months, 30 months, 24 months, or 18 months. In certain embodiments, the predetermined period is at least six months or at least twelve months. The present invention recognizes that in most cases, the more invasive the implantation method (e.g., surgical implantation), the more desirable it is to have a longer predetermined treatment period. In this way, the patient may minimize his or her exposure to the trauma associated with the implantation procedure. However, in some embodiments, the predetermined treatment period is relatively short (e.g., about three days, less than one week, about two weeks, or about three weeks). In some embodiments, the predetermined time is in a range of 1 day to 30 days, 1 day to 180 days, six months to twelve months, or one year to three years.

The present invention encompasses different methods of achieving a desired predetermined treatment period. For example, the duration of the predetermined treatment period may be adjusted by adjusting the physical length of the sustained release device, assuming that the sustained release device in question is administered at a rate proportional to the area of the drug core exposed to the body fluid of the patient. The duration of the predetermined treatment period may also be adjusted by appropriate selection of the bioerodible polymer to be mixed with the pharmaceutically active agent in the drug core. By way of non-limiting example, when the bioerodible polymer is polyvinyl alcohol, the polyvinyl alcohol can be heat treated to control or adjust the release rate of the pharmaceutically active agent. Typically, the heat treatment is performed after the pharmaceutically active agent is combined with the polyvinyl alcohol to form the intended matrix and/or diffusion port coating. However, the present invention also recognizes that in some instances, the core may be fully formed after the heat treatment, such that the polyvinyl alcohol coated film may be treated at higher temperatures to increase the polyvinyl alcohol crystallinity in order to further reduce the film permeability.

The above description of how to make the devices of the present invention is illustrative only and should not be construed as limiting the scope of the invention in any way, as the skilled person is familiar with the various compositions. In particular, the method of making the device depends on the identity of the active agent and polymer selected. One skilled in the art can readily manufacture the devices of the present invention using conventional coating techniques, taking into account the composition of the active agent and the polymer comprising the outer member and its delivery port.

A method of treating a mammalian organism to obtain a desired local or systemic physiological or pharmacological effect comprises: administering a sustained release drug delivery device of the present invention to a mammalian organism; and allowing the agent to pass through the device to directly contact the mammalian organism.

The drug delivery system of the present invention may be administered to a mammalian organism via any route of administration known in the art. Such routes of administration include intraocular, oral, subcutaneous, intramuscular, intraperitoneal, intravitreal, intracameral, intranasal, dermal, into the brain (including intracranial and epidural), into the joints (including ankle, knee, hip, shoulder, elbow, wrist), directly into tumors, and the like. Further, one or more devices may be administered at a time, or more than one agent may be included in the inner core or reservoir, or more than one reservoir may be provided in a single device.

The drug delivery system of the present invention is particularly suitable for direct implantation or injection into the vitreous of the eye, and for application to intraocular lenses.

These methods of administration, as well as techniques for their preparation, are well known to those of ordinary skill in the art. The preparation technology is described in Remington's Pharmaceutical Sciences.

The drug delivery system may be administered for a sufficient period of time and allow for the treatment of a disease state of interest under a variety of conditions.

For local drug delivery, the device may be surgically implanted at or near the site of action. This is the case where the device of the invention is used to treat eye disease, primary tumours, rheumatism and arthropathy, and chronic pain.

For systemic relief, the device may be implanted subcutaneously, intramuscularly, intra-arterially, intrathecally, or intraperitoneally. This is the case where the device will deliver sustained systemic levels and avoid premature metabolism. In addition, such devices may be administered orally.

In one embodiment of the present invention, ophthalmic devices may be prepared comprising as an effective agent a therapeutically effective amount of fluocinolone acetonide for reducing or preventing ocular neovascularization. Such devices can be used to effectively combat and inhibit undesirable ocular neovascularization, edema, or inflammation when surgically implanted into the vitreous of the eye. Preferred amounts of fluocinolone acetonide used in these devices range from about 0.01mg to about 40 mg. More preferably, such devices contain from about 0.1mg to about 6mg of fluocinolone acetonide. These preferred ranges can provide sustained release of fluocinolone acetonide over a period of hours to over five years.

When such devices are prepared for implantation within the vitreous of the eye, it is preferred that the device be no more than about 7 millimeters in any orientation so that the device can be inserted through an incision of less than 7 millimeters. Thus, the cylindrical device shown in the drawings preferably does not exceed 7 mm in height or 3 mm in diameter. The preferred size of the core is 3.5mm L

The preferred thickness of the bioerodible outer member ranges from 0.01mm to about 1.0 mm. Preferred thicknesses for the permeable bioerodible polymer layer used to make the delivery port range between about 0.01mm and about 1.0 mm. The preferred thickness of the wall of the outer layer ranges between about 0.01mm and 1.0 mm.