Surgery – Controlled release therapeutic device or system – Osmotic or diffusion pumped device or system
Reexamination Certificate
2001-04-19
2003-10-14
Casler, Brian L. (Department: 3763)
Surgery
Controlled release therapeutic device or system
Osmotic or diffusion pumped device or system
C604S891100
Reexamination Certificate
active
06632217
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 implantable osmotic pump systems.
2. Description of the Related Art
Since the beginning of modem 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 typically reduce the efficacy of medication by about 33%. Furthermore, oral medications must be administered by the patient. Patient compliance to the prescribed delivery profile is often poor. Studies suggest that 40% of patients do not comply with their oral medication consumption instructions. This causes two concerns. First, patients who do not take their medication as instructed are not maintaining blood drug levels within the therapeutic window and are therefore not receiving adequate therapy for their disease. A second, worse scenario than receiving too little medication occurs when the patient may be taking too much medication either by accident or purposefully in order to make up for a missed dose. Both of these patient-controlled scenarios can be dangerous to the patient, and at a minimum may prolong or aggravate their disease. Subcutaneous drug delivery and intravenous drug delivery have 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 if the therapy is intended to last longer than a few hours and the patient desires to be ambulatory. Subcutaneous drug delivery can be either partially implanted or totally implanted. Partially implanted systems rely on a percutaneous catheter or needle stick to deliver the medication, therefore, partially implanted systems have the same limitations as IV systems. Totally implanted systems have fewer maintenance requirements and are far less prone to infection than IV or partially implanted systems.
In the 1970s, a new approach toward sustained drug delivery was commercialized for animal use only. The driving force of such pumps was based upon a new approach utilizing the principle of osmosis. 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 right-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 semipermeable 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.
A limitation of the osmotic pump disclosed in the above-identified patent, however, is that its infusion rate cannot be adjusted once it is implanted. This is acceptable for medications that do not need rate adjustment, but often physicians desire to adjust the infusion rate based on the clinical status of the patient. One example of when a physician would want to increase the infusion rate is in the field of pain management. Osmotic pumps can be used to deliver medication to treat pain lasting over an extended period of time. Pain, however, often increases with time, and sometimes patients become tolerant to pain medications; therefore, more medication is needed to effectively treat the pain. The system disclosed in the above-identified patent does not allow a rate increase after implantation, so the physician must surgically remove the current implant and implant an additional pump to deliver the correct dosage. However, the prospect of yet another surgical procedure may cause many patients to forego the potential benefits of the larger dose and may also cause their physicians to advise against the initial procedure altogether.
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 right-cylindrical cavities in which to implant such devices in the patient, in an unobtrusive and comfortable manner.
What are needed, therefore, are improved osmotic pumps. What are also needed are improved 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 pumps for long term delivery of a pharmaceutical agent that do not rely upon a right-cylindrical pharmaceutical agent compartment and/or conventional cylindrical pistons. Also needed are implantable pumps that enable the physician to increase the dose of pharmaceutical agent delivered to the patient without, however, removing the pump from the implant site.
SUMMARY OF THE INVENTION
It is an object of the present invention, therefore, to provide improved pumps. Another object of the present invention is to provide improved implantable osmotic pumps that conform to the patient's anatomy and that more closely match the topology of the implant site. A still further object is to provide novel implantable osmotic pumps for long term delivery of a pharmaceutical agent that do not rely upon a right-cylindrical pharmaceutical agent compartment and/or conventional cylindrical pistons. Preferably, such improved pumps should enable the physician to increase the dose of pharmaceutical agent delivered to the patient without removing the pump from the implant site.
In accordance with the above-described objects and those that will be mentioned and will become apparent below, an implantable osmotic pump for delivering a pharmaceutical agent to a patient, according to an embodiment of the present invention, includes an osmotic engine; a substantially toroidal compartment adapted to store a pharmaceutical agent, and a piston disposed within the compartment, the osmotic engine being configured to cause the piston to travel within the compartment and deliver the pharmaceutical agent when the pump is implanted in the patient.
The pump may include a tube coiled at least partially around the osmotic engine, an inner lumen of the tube defining the pharmaceutical agent compartment. The tube may include or be formed of metals, polymers and/or polyimid, for example. The compartment may be disposed at least partially around the osmotic engine. The tube may be rigid and the osmotic engine may be disposed within the tube.
According to other embodiments, the osmotic engine may include a base, a cylindrical wall attached to the base and a free end opposite the base. The pump may include a housing configured to enclose at least the osmotic engine and the tube. The housing may include a first housing half and a second housing half that mates with the first housing half. Each of the first and second housing halves may define a saucer shape, for example. Each of the first and the second housing halves may be substantially circular in shape. The first housing half may define a substantially circular opening. The pump may further include a membrane enclosure, the membrane enclosure being partially surrounded by the osmotic engine and including an initial dose semipermeable membrane that is configured to allow water from the patient to reach the osmotic engine when the pump is implanted. The pump may be configured to deliver an initial dose of the pharm
Harper Derek J.
Milo Charles F.
Casler Brian L.
Lam Ann Y.
MicroSolutions, Inc.
Young Law Firm P.C.
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