Surgery – Controlled release therapeutic device or system – Osmotic or diffusion pumped device or system
Reexamination Certificate
2000-02-15
2002-10-15
Jacyna, J. Casimer (Department: 3751)
Surgery
Controlled release therapeutic device or system
Osmotic or diffusion pumped device or system
C604S891100
Reexamination Certificate
active
06464688
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of drug delivery systems. In particular, the present invention relates to osmotic pump systems.
2. Description of the Related Art
Since the beginning of modern medicine, drugs have been administered orally. Patients have taken pills as recommended by their physician. The pills must pass through the digestive system and then the liver before they reach their intended delivery site (e.g., the vascular system). The actions of the digestive tract and the liver often reduce the efficacy of medication; furthermore, medications delivered systemically sometimes cause undesirable side effects. Over the course of the past few decades, drug delivery technology and administration has evolved from oral delivery to site-specific delivery. In addition to the oral route of administration, drugs are also routinely administered via the vascular system (intravenous or IV). Intravenous drug delivery has the advantage of bypassing the acidic and enzymatic action of the digestive system. Unfortunately, IV administration requires the use of a percutaneous catheter or needle to deliver the drug to the vein. The percutaneous site requires extra cleanliness and maintenance to minimize the risk of infection. Infection is such a significant risk that IV administration is often limited to a number of weeks, at most. In addition, the patient must wear an external pump connected to the percutaneous catheter.
The next step in the evolution of drug delivery was the implanted pump. The implanted pump is a device that is completely implanted under the skin of a patient, thereby negating the need for a percutaneous catheter. These implanted pumps provide the patient with a drug at a constant or a programmed delivery rate. Constant rate or programmable rate pumps are based on either phase-change or peristaltic technology. When a constant, unchanging delivery rate is required, a constant-rate pump is well suited for long-term implanted drug delivery. If changes to the infusion rate are expected, a programmable pump may be used in place of the constant rate pump. Fully implanted constant rate and programmable rate infusion pumps have been sold in the United States for human use since the late 1970s and early 1980s, respectively. Two problems associated with such 1970s and 1980s vintage constant rate and programmable rate infusion pumps relate to their size and their cost. Current implantable constant rate and programmable pumps are about the size and shape of hockey pucks, and they typically are sold to the hospital for $5,000-$9,000. The current implantable pumps must be implanted in the Operating Room under general anesthesia, which further increases costs, as well as the risk, and discomfort to the patient. The size and cost of such pumps has proven to be a substantial barrier to their use, and they are rarely used to deliver medication. An added drawback of phase-change and peristaltic pumps is that they must be refilled with drug every 3-8 weeks. Refills constitute an added burden to the caregiver, and add further costs to an already overburdened healthcare system. The burden associated with such refills, therefore, further limits the use of phase-change and peristaltic pumps.
In the 1970s, a new approach toward implanted pump design was commercialized for animal use only. The driving force of the pumps based upon this new approach utilized the principle of osmosis. Osmotic pumps may be much smaller than other constant rate or programmable pumps, because their infusion rate can be very low. A recent example of such a pump is described listed in U.S. Pat. No. 5,728,396. This patent discloses an implantable osmotic pump that achieves a sustained delivery of leuprolide. The pump includes a cylindrical impermeable reservoir that is divided into a water-swellable agent chamber and a drug chamber, the two chambers being divided by a movable piston. Fluid from the body is imbibed through a semi permeable membrane into the water-swellable agent chamber. As the water-swellable agent in the water-swellable agent chamber expands in volume, it pushes on the movable piston, which correspondingly decreases the volume of the drug chamber and causes the drug to be released through a diffusion outlet at a substantially constant rate.
The aspect ratio of such cylindrical osmotic pump delivery devices is large, and often not compatible with the human body. Indeed, the human body does not have naturally-formed cylindrical cavities in which to implant such devices in the patient, in an unobtrusive and comfortable manner. The principal reason for the cylindrical designs of conventional osmotic pump drug delivery systems is that they rely upon a movable piston design to push out a volume of drug from the drug chamber as the osmotic water-swellable agent expands. Pistons, however, must be cylindrical to avoid binding the pump housing as the piston moves. This problem is exacerbated by the fact that the water-swellable agent within the water-swellable agent compartment often does not expand evenly, which may exert localized increased pressure on the piston, causing the piston to bind within the pump housing. In turn, this binding may affect the delivery rate of the device and reduce the therapeutic benefits of the implantable pump.
What are needed, therefore, are non-cylindrical implantable osmotic pumps. What are also needed are implantable osmotic pumps that conform to the patient's anatomy and that more closely match the topology of the implant site. Also needed are novel implantable osmotic pump designs that do not rely upon a piston to infuse a drug or drugs into the patient.
SUMMARY OF THE INVENTION
It is an object of the present invention, therefore, to provide non-cylindrical implantable osmotic pumps. It is also an object of the present invention to provide implantable osmotic pumps that conform to the patient's anatomy and that more closely match the topology of the implant site. Another object of the present invention is to provide novel implantable osmotic pump designs that do not rely upon a piston to infuse a drug or drugs into the patient.
In accordance with the above-described objects and those that will be mentioned and will become apparent below, an implantable osmotic pump system, according to an embodiment of the present invention, includes a rigid pump housing defining an opening; at least one membrane assembly fitted to the pump housing; an osmotic engine within the rigid pump housing, and a flexible pharmaceutical agent compartment disposed within the rigid pump housing, the flexible pharmaceutical agent compartment being in fluid communication with the opening.
According to further embodiments, the membrane assembly may include a semipermeable membrane and may include an impermeable membrane initially sealing the semipermeable membrane, the impermeable membrane being adapted to be breached by a lancet. The impermeable membrane may be disposed away from the semipermeable membrane to define a fluid tight compartment therewith, which compartment may enclose a volume of saturated saline solution. The impermeable membrane may include a biologically inert material that is impermeable to water and that may be radiopaque. The impermeable membrane may include titanium, steel, polyethylene, polyethylene teraphthalate (PET), PETG and/or PETE. The impermeable membrane may include or be coated with a layer of gold, silver, platinum and/or platinum-iridium, for example.
The osmotic engine may include a “conventional” osmotic engine. Instead of a “salt block”, the osmotic engine may include a “salt wafer”. The osmotic engine may be a hygroscopic salt and/or may include an absorbent polymer. The absorbent polymer may include a material selected from a group including poly(acrylic acid), potassium salt; poly(acrylic acid), sodium salt; poly(acrylic acid-co-acrylamide), potassium salt; poly(acrylic acid), sodium salt-graft-poly(ethylene oxide); poly (2-hydroxethyl methacrylate); poly(2-hydroxypropyl methacrylate)
Harper Derek J.
Milo Charles F.
Jacyna J. Casimer
MicroSolutions, Inc.
Young Law Firm P.C.
LandOfFree
Osmotic pump delivery system with flexible drug compartment does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Osmotic pump delivery system with flexible drug compartment, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Osmotic pump delivery system with flexible drug compartment will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3000399