| Osmotic pump with means for dissipating internal pressure -> Monitor Keywords |
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Osmotic pump with means for dissipating internal pressureRelated Patent Categories: Surgery, Controlled Release Therapeutic Device Or SystemOsmotic pump with means for dissipating internal pressure description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070191818, Osmotic pump with means for dissipating internal pressure. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of application Ser. No. 10/814,801, filed Mar. 31, 2004, pending, which claims the benefit of the filing date of provisional patent application Ser. No. 60/459,296, filed Mar. 31, 2003, for "Osmotic Pump With Means For Dissipating Internal Pressure." The disclosure of each of the previously referenced U.S. patent applications is hereby incorporated by reference in its entirety. FIELD OF THE INVENTION [0002] The present invention relates to implantable osmotic pumps providing sustained delivery of a drug. In particular, the present invention is directed to an implantable osmotic pump including a vent that allows gradual venting of osmotic material after the drug formulation included in the osmotic pump is delivered. BACKGROUND [0003] Implantable, controlled-release osmotic pumps (hereinafter "osmotic pumps") are known in the art. For example, U.S. Pat. Nos. 3,797,492, 3,987,790, 4,008,719, 4,865,845, 5,057,318, 5,059,423, 5,112,614, 5,137,727, 5,151,093, 5,234,692, 5,234,693, 5,279,608, 5,336,057, 5,728,396, 5,985,305, 5,997,527, 5,997,902, 6,113,938, 6,132,420, 6,217,906, 6,261,584, 6,270,787, and 6,375,978, which are assigned to ALZA Corporation of Mountain View, Calif., and are herein incorporated in their entirety by reference, describe various osmotic pumps. The osmotic pumps described in these references may be designed for implantation in a subject of choice and may be configured to deliver a range of drugs at various rates over predetermined periods of time. [0004] Osmotic pumps typically include a reservoir for containing an amount of drug formulation, an osmotic composition, a semipermeable membrane, a delivery orifice, and a piston separating the drug formulation from the osmotic composition. Upon administration to an environment of operation, water is drawn through the semipermeable membrane of the osmotic pump into the osmotic composition, causing the osmotic composition to swell. As the osmotic composition swells, the piston included in the osmotic pump is driven through its stroke, resulting in the expulsion of the drug formulation at a controlled rate through the delivery orifice. The rate of drug release from an osmotic pump may be adjusted by altering the composition or amount of the drug formulation or the osmotic composition included in the osmotic pump. Alternatively, the release rate of drug formulation provided by an osmotic pump may be adjusted by altering the composition or exposed surface area of the semipermeable membrane. Because they allow the controlled delivery of active agent over periods of weeks, months, or even years, osmotic pumps can advantageously provide long-term dosing of a desired drug without requiring frequent visits to a healthcare provider or repetitive self-medication. Therefore, osmotic pumps can work to provide increased patient compliance, reduced irritation at the site of administration, fewer occupational hazards for healthcare providers, reduced waste hazards, and increased therapeutic efficacy through enhanced dosing control. [0005] As drug formulation is delivered from an osmotic pump, the internal pressure generated by the osmotic composition within the pump generally remains relatively low. However, if an osmotic system is left within an environment of operation after the piston included in the osmotic pump reaches the end of its stroke within the reservoir (e.g., after substantially all the drug formulation has been delivered), the osmotic composition will continue to draw water in from the environment of operation. As water is drawn into the osmotic pump without expulsion of a corresponding amount of drug formulation, the pressure within the system may rise to such an extent that a component of the osmotic pump is compromised or physically separated. Where the semipermeable membrane included in an osmotic pump is held in place through a friction fit, such as is described in, for example, U.S. Pat. Nos. 5,985,305, 5,728,396, and 6,156,331, the semipermeable membrane is one of the components that is most likely to be separated from the osmotic pump if the internal pressure of the osmotic system increases well beyond normal operational pressures. [0006] It would, therefore, be an improvement in the art to provide an osmotic pump that allows the placement of a semipermeable membrane through a friction fit mechanism, yet works to prevent a pressure build-up within the pump that results in the dissociation of pump components, such as the semipermeable membrane. Though not likely to be harmful to a subject, the physical separation of one or more components of an implanted osmotic pump may complicate removal of the device from a subject. Moreover, the physical separation of the semipermeable membrane of an osmotic pump may allow a relatively sudden release of the material forming the osmotic composition, which may result in localized discomfort or inflammation. Thus, where an implantable osmotic pump is designed to dissipate internal pressure before such pressure reaches a level that could cause dissociation of one or more parts, the design of the osmotic pump would ideally allow pressure dissipation without causing a release of osmotic material that results in discomfort or inflammation. SUMMARY OF THE INVENTION [0007] The present invention is directed to an osmotic pump that includes a means for venting the osmotic composition included therein before the internal pressure of the pump has the opportunity to build to such an extent that the pump is structurally compromised, such as when one or more components of the pump are physically separated. The means for venting osmotic material included in an osmotic pump according to the present invention includes a vent that allows the material included in the osmotic composition of the pump to dissipate into an environment of operation, resulting in a reduction of the internal pressure [0008] The vent included in an osmotic pump of the present invention is formed through the reservoir of the osmotic pump and is positioned such that the vent is sealed from the osmotic composition under normal operating conditions. However, the vent is also positioned in the reservoir such that, if the pressure within the osmotic pump reaches a magnitude that results in displacement of one or more components, the vent is opened or exposed to the materials forming the osmotic composition, which allows release of materials forming the osmotic composition into the environment of operation and results in the dissipation of the internal pressure before one or more components of the osmotic pump fails or is separated from the device. In addition, because an osmotic pump according to the present invention can be designed without compressive elements, the maximum rate of material expulsion from the vent will typically match the targeted release rate of the osmotic pump. Therefore, an osmotic pump according to the present invention can be easily designed to allow venting of the osmotic composition, while reducing or minimizing the likelihood that such venting will result in discomfort or irritation to the subject. [0009] In a preferred embodiment, an osmotic pump includes a vent that is sealed by the semipermeable membrane of the osmotic pump during normal operating conditions. The semipermeable membrane of such an embodiment is friction fit within the reservoir and is designed to allow progressive displacement of the semipermeable membrane once a threshold pressure is reached within the osmotic pump. The vent included in this embodiment of the present invention is positioned such that, if the internal pressure reaches the threshold pressure and the semipermeable membrane begins to be displaced relative to the reservoir, the vent is exposed well before the semipermeable membrane is separated from the device. Once the vent is exposed, the osmotic materials included in the osmotic composition may be expelled from the osmotic pump, resulting in a decrease in pressure within the pump and preventing separation of the semipermeable membrane. BRIEF DESCRIPTION OF THE DRAWINGS [0010] The present invention is described with reference to the accompanying drawings in which like elements bear like reference numerals, and wherein: [0011] FIG. 1 provides a schematic illustration of one embodiment of an osmotic pump according to the present invention. [0012] FIG. 2 provides a schematic illustration of the osmotic pump shown in FIG. 1 as the pump functions to deliver drug formulation to an environment of operation. [0013] FIG. 3 provides a schematic illustration of the osmotic pump shown in FIG. 1 and FIG. 2 as delivery of the drug formulation is completed and the piston included in the osmotic pump reaches the end of its stroke within the reservoir. [0014] FIG. 4 provides a schematic illustration of the osmotic pump shown in FIG. 1 through FIG. 3 after the internal pressure of the osmotic pump has caused displacement of the semipermeable membrane, the vent has been exposed, and the osmotic composition is venting into the environment of operation. DETAILED DESCRIPTION OF THE INVENTION [0015] An osmotic pump 10 according to the present invention is illustrated in FIG. 1. As can be seen by reference to these figures, an osmotic pump 10 according to the present invention includes a reservoir 12, a drug formulation 14, an osmotic composition 16, a piston 18, a semipermeable membrane 22, a delivery orifice 24, and a vent 26 formed through the wall 20 of the reservoir 12. However, the configuration of the osmotic pump 10 illustrated in FIG. 1 provides only one example of an osmotic pump according to the present invention and is not to be construed as limiting the present invention. The present invention is generally applicable to osmotic pumps, and an osmotic pump according to the present invention may be designed to conform to a wide range of desired sizes or shapes. Moreover, an osmotic pump according to the present invention may be designed for application in various environments or administration by various routes, such as by oral administration, ruminal administration, or implantation. [0016] The reservoir 12 of the osmotic pump 10 of the present invention may be sized and shaped as desired to suit a desired application or to facilitate placement of the osmotic pump 10 in a desired environment of operation. Materials suitable for forming the reservoir 12 must be sufficiently strong to ensure that the reservoir 12 does not leak, crack, break, or significantly distort under stresses to which it is subjected to during administration and operation of the osmotic pump 10. In particular, the reservoir 12 is formed of a material that is sufficiently rigid to withstand expansion of the osmotic composition 16 without undergoing substantial changes to the size or shape of the reservoir 12. The material used to form the reservoir 12 is also chosen to be largely impermeable to fluids from the environment of operation and to the material constituents included in the drug formulation 14 and the osmotic composition 16. As it is used herein the term "largely impermeable" indicates that the migration of materials into or out of the osmotic pump through the material forming the reservoir 12 is so low that any such migration of materials has substantially no adverse impact on the function of the device. [0017] The material used to form the reservoir 12 of an osmotic pump 10 according to the present invention is preferably not a bioerodible material and will remain intact even after the drug formulation 14 has been delivered. Such a design facilitates recovery or passage of the osmotic pump 10 after the drug formulation 14 contained therein has been delivered to a subject. Typical materials suitable for the construction of the reservoir 12 of an osmotic pump 10 according to the present invention include, but are not limited to, nonreactive polymers and biocompatible metals and alloys. Specific examples of suitable polymers include, but are not limited to, polyimide, polysulfone, polycarbonate, polyethylene, polypropylene, polyvinylchloride-acrylic copolymer, polycarbonate-acrylonitrile-butadiene-styrene, polystyrene, acrylonitrile polymers, such as acrylonitrile-butadiene-styrene terpolymer and the like, halogenated polymers, such as polytetrafluoroethylene, polychlorotrifluoroethylene copolymer, tetrafluoroethylene and hexafluoropropylene. Metallic materials useful in forming the reservoir 12 include, but are not limited to, stainless steel, titanium, platinum, tantalum, gold, and their alloys, as well as gold-plated ferrous alloys, platinum-plated ferrous alloys, cobalt-chromium alloys, and titanium nitride coated stainless steel. [0018] The semipermeable membrane 22 included in an osmotic pump 10 of the present invention is formulated and prepared to be permeable to the passage of external liquids, such as water and biological liquids, but substantially impermeable to the passage of the drug, osmopolymers, osmagents, and the like that may be included in the osmotic pump 10. Suitable materials and methods for forming the semipermeable membrane 22 included in an osmotic pump 10 of the present invention are well known in the art and are detailed in, for example, U.S. Pat. Nos. 3,797,492, 3,987,790, 4,008,719, 4,865,845, 4,874,388, 5,057,318, 5,059,423, 5,112,614, 5,137,727, 5,151,093, 5,234,692, 5,234,693, 5,279,608, 5,336,057, 5,728,396, 5,985,305, 5,997,527, 5,997,902, 6,113,938, 6,132,420, 6,217,906, 6,261,584, 6,270,787, and 6,375,978, the contents of which are herein incorporated in their entirety by this reference. Such possible semipermeable materials from which the semipermeable membrane 22 can be made include, but are not limited to, for example, Hytrel polyester elastomers (DuPont), cellulose esters, cellulose ethers, and cellulose ester-ethers, water flux enhanced ethylene-vinyl acetate copolymers, semipermeable membranes made by blending a rigid polymer with water-soluble low molecular weight compounds, and other semipermeable materials well known in the art. The above cellulosic polymers have a degree of substitution, D.S., on the anhydroglucose unit, from greater than 0 up to 3 inclusive. By "degree of substitution," or "D.S.," is meant the average number of hydroxyl groups originally present on the anhydroglucose unit comprising the cellulose polymer that is replaced by a substituting group. Representative materials include, but are not limited to, one selected from the group consisting of cellulose acylate, cellulose diacylate, cellulose triacylate, cellulose acetate, cellulose diacetate, cellulose triacetate, mono-, di-, and tricellulose alkanylates, mono-, di-, and tricellulose aroylates, and the like. Exemplary cellulosic polymers include cellulose acetate having a D.S. up to 1 and an acetyl content up to 21%; cellulose acetate having a D.S. of 1 to 2 and an acetyl content of 21% to 35%; cellulose acetate having a D.S. of 2 to 3 and an acetyl content of 35% to 44.8%, and the like. More specific cellulosic polymers include cellulose propionate having a D.S. of 1.8 and a propionyl content of 39.2% to 45% and a hydroxyl content of 2.8% to 5.4%; cellulose acetate butyrate having a D.S. of 1.8 and an acetyl content of 13% to 15% and a butyryl content of 34% to 39%; cellulose acetate butyrate having an acetyl content of 2% to 29%, a butyryl content of 17% to 53%, and a hydroxyl content of 0.5% to 4.7%; cellulose acetate butyrate having a D.S. of 1.8, an acetyl content of 4% average weight percent, and a butyryl content of 51%; cellulose triacylates having a D.S. of 2.9 to 3 such as cellulose trivalerate, cellulose trilaurate, cellulose tripalmitate, cellulose trisuccinate, and cellulose trioctanoate; cellulose diacylates having a D.S. of 2.2 to 2.6 such as cellulose disuccinate, cellulose dipalmitate, cellulose dioctanoate, cellulose dipentate; coesters of cellulose, such as cellulose acetate butyrate and cellulose, cellulose acetate propionate, and the like. Other materials that may be used to prepare a semipermeable membrane 22 useful in the osmotic pump 10 of the present invention include polyurethane, polyetherblockamide (PEBAX, commercially available from ELF ATOCHEM, Inc.), and injection-moldable thermoplastic polymers with some hydrophilicity such as ethylene vinyl alcohol (EVA). Continue reading about Osmotic pump with means for dissipating internal pressure... Full patent description for Osmotic pump with means for dissipating internal pressure Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Osmotic pump with means for dissipating internal pressure patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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