Surgery – Controlled release therapeutic device or system – Osmotic or diffusion pumped device or system
Reexamination Certificate
1998-12-22
2001-09-04
Kennedy, Sharon (Department: 3763)
Surgery
Controlled release therapeutic device or system
Osmotic or diffusion pumped device or system
C424S423000
Reexamination Certificate
active
06283953
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an osmotic beneficial agent delivery system. More particularly, the invention relates to a noninvasive monitoring system for monitoring the release of a beneficial agent from an implanted osmotic drug delivery system.
BACKGROUND OF THE INVENTION
Many different types of delivery systems for delivering beneficial agents such as pharmaceuticals for the prevention, treatment, and diagnosis of disease are known in the art. One type of delivery system is the osmotic delivery system in which an osmotic pressure gradient is created to draw an aqueous fluid into a beneficial agent containing member causing the beneficial agent to be delivered. Osmotic delivery systems generally include an implantable member forming a chamber containing the beneficial agent and an osmotic agent which draws an aqueous fluid through the walls of the implantable member causing swelling of the osmotic agent and delivery of the beneficial agent.
Some osmotic delivery systems include a single compartment implantable member and contain both the beneficial agent and the osmotic agent within this single compartment. These devices release the beneficial agent by allowing fluid to be imbibed through the wall of the implantable member into the compartment at a rate determined by the permeability of the wall and the osmotic pressure gradient across the wall. The fluid imbibed into the device mixes with the beneficial agent to form an aqueous solution which is dispensed through an exit passageway of the device. Although these devices are effective for delivery of a beneficial agent which is stable and soluble in aqueous and biological fluids, the devices are ineffective for delivery of many types of beneficial agents which are not soluble or stable in aqueous fluids. Examples of osmotic delivery systems of this type include those described in U.S. Pat. Nos. 3,845,770 and 3,916,899.
Improvements in osmotic delivery systems are described in U.S. Pat. Nos. 4,111,202; 4,111,203; and 4,203,439. In these patents the delivery kinetics of the devices has been improved by allowing delivery of beneficial agents without the requirement for the beneficial agent to be soluble in an aqueous type fluid. These improved implantable osmotic devices include a first beneficial agent compartment separated by a film or piston from a second osmotic compartment. In these devices, the beneficial agent is delivered by imbibing fluid through the wall of the device into the osmotic compartment. As the osmotic compartment fills with fluid, the osmotic agent within the compartment swells and acts as a driving force causing the film or piston to move against the beneficial agent and deliver the beneficial agent through a delivery passageway.
The various osmotic delivery systems are designed to deliver a beneficial agent at a controlled rate which will vary depending on many factors including the osmotic material used, the permeability of the walls, and the physical configuration of the delivery device. Although osmotic delivery devices generally operate very reliably to dispense the desired amount of beneficial agent at the desired rate, it would be beneficial to be able to monitor the delivery of beneficial agent. For example, it would be desirable to be able to detect when the beneficial agent within the delivery device has been completely dispensed and a new device may be needed. It would also be beneficial to detect a malfunction of the device, for example, in some types of osmotic delivery devices employing a piston which separates the osmotic agent and the beneficial agent the piston may become frozen causing the device to malfunction. In a addition, monitoring of the delivery rate of the beneficial agent would be desirable to more accurately monitor and control treatment.
Some methods which have been contemplated for monitoring drug delivery from osmotic delivery systems include the measurement of residual amounts of delivered drug in the patient, or radiolabeling the drug composition for detection by X-ray. However, these monitoring methods involve a time delay.
Drug delivery rate s are generally determined f or a particular implantable osmotic device by testing the unimplanted drug delivery device and collecting and measuring the delivered drug in a collection vessel. However, these tests will not account for varying conditions which the drug delivery device will encounter when it is actually implanted within the patient. Therefore, monitoring of the operation of the implanted osmotic drug delivery device would be desirable.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a noninvasive monitoring system for osmotic drug delivery devices which can be used to determine the piston position and/or the drug delivery rate for an implanted osmotic dry delivery device.
In accordance with the present invention, an osmotic delivery device for delivery of a beneficial agent to an animal includes an implantable reservoir having at least one opening for delivery of beneficial agent contained within an interior of the reservoir to an organ of an animal, an osmotic engine causing the release of the beneficial agent contained within the reservoir to the animal, and means for noninvasively measuring the release of the beneficial agent from the reservoir from outside of tissue in which the delivery device is implanted.
In accordance with a more detailed aspect of the invention, the means for noninvasively measuring the release of the beneficial agent from the reservoir includes a first radiopaque marker on a portion of the reservoir and a second radiopaque marker on a movable piston positioned within the reservoir and separating the beneficial agent from the osmotic engine.
In accordance with another more detailed aspect of the invention, the means for noninvasively measuring the release of the beneficial agent from the reservoir includes a magnetic piston positioned within the implantable reservoir between the osmotic engine and the beneficial agent. A gauge is provided for determining the position of the magnetic piston from an exterior of the animal.
In accordance with a further more detailed aspect of the present invention, the means for noninvasively measuring the release of the beneficial agent from the reservoir includes a marker incorporated in the beneficial agent. The marker provides a detectable response which can be measured noninvasively in body fluids or by-products to monitor release of the beneficial agent within the animal.
In accordance with another aspect of the present invention, a method of monitoring performance of an osmotic drug delivery system includes implanting an osmotic drug delivery device having a movable piston in an animal and determining a position of the implanted movable piston within the osmotic drug delivery device from an exterior of the animal.
The present invention provides the advantage of noninvasive, real time monitoring of the performance of an implanted osmotic drug delivery system.
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Ayer Rupal
Berry Stephen A.
Eckenhoff Bonnie J.
Eckenhoff James B.
Jordan Scott D.
ALZA Corporation
Clarke Pauline A.
Eckenhoff Bonnie J.
Kennedy Sharon
Lynch Cindy A.
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