Surgery – Controlled release therapeutic device or system
Reexamination Certificate
2001-03-02
2003-05-27
Huson, Gregory L. (Department: 3751)
Surgery
Controlled release therapeutic device or system
C604S892100, C424S422000, C424S472000
Reexamination Certificate
active
06569152
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to delivery systems that allow for sustained release of one or more solutes. In particular, the present invention relates to devices for delivering substances to the body of an animal or into other environments requiring a constant delivery and to methods of delivering these substances in a constant, sustained-release fashion.
BACKGROUND OF THE INVENTION
Drug delivery classically has been via oral dosage forms that release the drug as they dissolve in the gastrointestinal tract. These delivery systems typically provide for rapid release of the active substance, which leads to the presence of maximal concentrations of the drug in the blood followed by a rapid decrease in concentration as the drug is metabolized and cleared. At these maximal concentrations, many drugs are highly toxic. Furthermore, if the concentration decreases rapidly in the body, then the time during which there is a therapeutically-effective level is short, and therapeutic efficacy requires administration of multiple doses. In addition, if release of a substance in the body cannot be controlled, then it may not be effectively delivered to the site of the body requiring treatment.
Other solutes also benefit from devices that allow for their sustained release. For example, dosing of swimming pools with chlorine or hot tubs with bromine as anti-microbial agents currently requires adding these substances to the water on a fairly regular basis. Furthermore, if the concentration is not controlled and becomes too high upon addition, then the water may not be safe or pleasant for bathers until the concentration stabilizes at lower values. Other uses for sustained-release delivery systems include, for example, delivery of food or insecticides to plants, delivery of vaccines, antibiotics, anti-parasitic agents, growth promotants or other drugs to livestock, delivery of sanitizing agents or perfumes to toilets or septic tanks, delivery antibiotics or other drugs to companion animals, delivery of dyes, bleaches or other substances in the processing of textiles, delivery of algicides to water towers or ponds, delivery of food to fish in aquaria or ponds, and delivery of any substance requiring constant delivery in an industrial manufacturing process.
Various sustained release delivery devices have been described, including those in which a solute is contained within an impermeable housing with one or more openings from which solute egresses by diffusion. Such devices purport to deliver solute at a constant (zero-order) rate; however, many deviate significantly from zero order or linear delivery. In addition, such devices often are limited in the amount of total dose deliverable, as well as by fixed parameters that make it difficult or impossible to adjust the delivery kinetics. A common feature of such prior art devices is that their release kinetics are characterized by an initial burst of solute release prior to a period of relatively constant rate of release, and the relatively constant rate of release often only crudely approximates zero order. For several reasons, such an initial burst is undesirable, as it temporarily delivers a dose in excess of the desired, effective dose, thus wasting solute, and moreover, may deliver an amount of solute which is toxic or otherwise damaging in the particular application. In addition, the initial release of a large amount of solute reduces the total amount of solute subsequently available for prolonged release by the device, thus shortening the duration of relative constant delivery, reducing its effective life and requiring more frequent replacement.
The devices and methods of the present invention overcome the disadvantages of current devices and methods for the delivery of solutes by providing for reliable and adjustable sustained release of solutes in aqueous and non-aqueous environments. In addition to exhibiting adjustable, nearly-constant release rates over suitably prolonged periods of time, the devices and methods of the invention provide for modulation or suppression of the aforementioned initial burst. The devices and methods of the invention may be applied to any of the prior-art devices relying on a fenestration or orifice and a fluid- and solute-impervious coating, to provide prolonged and near zero-order release.
Discussion or citation of a reference herein shall not be construed as an admission that such reference is prior art to the present invention.
SUMMARY OF THE INVENTION
In a first embodiment, the present invention relates to a device for the continuous, linear, sustained release of one or more solutes. The device comprises at least one dispenser, each dispenser comprising at least one solute reservoir element, the solute reservoir element defined by a fluid-impervious and solute-impervious wall and having at least one orifice therein referred to as a source element, each source element being in fluid registry with a gradient-forming element, the gradient-forming element having a release orifice. The gradient-forming element is provided for preventing unwanted initial burst and release of solute while promoting controlled, prolonged near-zero-order release.
The solute reservoir element may have a shape such as but not limited to a hemisphere, sphere, pyramid, cylinder, tetrahedron, parallelepiped, or polyhedron. A hemisphere- or pyramid-shaped solute reservoir element is preferred. A hemispherical solute reservoir element is most preferred. Preferably, the ratio of the radius of a hemisphere or portion thereof representing the maximum internal diffusion surface of the solute reservoir element, to the radius of the source element, is equal to or greater than about two, and more preferably, the ratio is greater than or equal to about five. Most preferably, the ratio is equal to or greater than about ten.
The source element is an opening or passageway between the solute reservoir element and the gradient-forming element. It preferably has a circular cross-section but is not so limiting, and may have any shape.
The gradient-forming element may have a shape such as but not limited to a hemisphere, sphere, pyramid, cylinder, tetrahedron, parallelepiped, or polyhedron. Preferably, the gradient-modifying element is a pyramid, the most preferable pyramid a truncated right circular cone (a frustum). More preferred is a right circular cone with a vertex angle of between about 10° and about 135°, and even more preferred is a vertex angle of about 60° to about 120°. Preferably, the relationship among the dimension of the gradient-forming element extending from the source element to the release orifice (referred to herein as the height of the gradient-forming element) and the radii of the release orifice and the source element are such that the height of the gradient-forming element is less than about four times the ratio of the square of the radius of the source element to the radius of the release orifice. More preferably, the height of the gradient-forming element is less than about two times the aforementioned ratio, and most preferably, the height of the gradient-forming element is less than two times the aforesaid ratio but greater than one-tenth the aforementioned ratio.
In another preferred embodiment of the present invention, the foregoing device has a cylindrical gradient-forming element, one end of the cylinder in fluid registry with the source element, and the other end providing the release orifice. Preferably, the ratio of the radius of the hemisphere comprising the solute reservoir element to the radius of the source element is equal to or greater than about two, more preferably equal to or greater than five, and most preferably equal to or greater than ten. The height of the cylinder is preferably less than about four times its radius, more preferably less than about two times its radius, and most preferably 0.1 to 2 times its radius. Such devices are particularly useful for oral delivery of a therapeutic agent, although it is not so limiting.
In another embodiment, the device of the present invention m
Brines Michael
Cerami Anthony
Wuerth Jean-Paul
Farrington Pharmaceuticals, LLC
Huson Gregory L.
Klauber & Jackson
Ramana Anuradha
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