Surgery – Controlled release therapeutic device or system
Reexamination Certificate
2000-12-20
2003-10-14
Mendez, Manuel (Department: 3763)
Surgery
Controlled release therapeutic device or system
Reexamination Certificate
active
06632216
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Priority is claimed to Great Britain patent application No. 9930000.6 filed on Dec. 21, 1999.
BACKGROUND TO THE INVENTION
The present invention relates to an ingestible device. In particular the invention relates to such a device in the form of a capsule that is intended to release a controlled quantity of a substance, such as a pharmaceutically active compound, foodstuff, dye, radiolabelled marker, vaccine, physiological marker or diagnostic agent at a chosen location in the gastrointestinal (GI) tract of a mammal. Such a capsule is sometimes referred to as a “Site-Specific Delivery Capsule”, or SSDC.
SSDC 's have numerous uses. One use of particular interest to the pharmaceutical industry involves assessing the absorption rate and/or efficacy of a compound under investigation, at various locations in the GI tract. Pharmaceutical companies can use data obtained from such investigations, e.g. to improve commercially produced products.
Several designs of SSDC are known. One design of capsule intended for use in the GI tract of a mammal is disclosed in “Autonomous Telemetric Capsule to Explore the Small Bowel”, Lambert et al, Medical & Biological Engineering and Computing, March 1991. The capsule shown therein exhibits several features usually found in such devices, namely:
a reservoir for a substance to be discharged into the GI tract;
an on-board energy source;
a mechanism, operable under power from the energy source, for initiating discharge of the substance from the reservoir;
a switch, operable remotely from outside the body of the mammal, for initiating the discharge; and
a telemetry device for transmitting data indicative of the status, location
and/or orientation of the capsule.
Also, of course, the dimensions of the capsule are such as to permit its ingestion via the oesophagus; and the external components of the capsule are such as to be biocompatible for the residence time of the capsule within the body.
The capsule disclosed by Lambert et al suffers several disadvantages. Principal amongst these is the complexity of the device. This means that the capsule is expensive to manufacture. Also the complexity means that the capsule is prone to malfunction.
For example, the capsule disclosed by Lambert et al includes a telemetry device that is initially retracted within a smooth outer housing, to permit swallowing of the capsule via the oesophagus. Once the capsule reaches the stomach, gastric juice destroys a gelatin seal retaining the telemetry device within the housing. The telemetry device then extends from the housing and presents a rotatable star wheel that engages the wall of the GI tract. Rotations of the star wheel generate signals that are transmitted externally of the capsule by means of an on-board RF transmitter powered by a battery within the capsule housing.
This arrangement may become unreliable when used in mammals whose GI motility is poor or whose gastric juice composition is abnormal.
There is a risk of malfunction of the rotating part of the telemetry device, and the method of operation of the capsule is generally complex.
The space needed to house the telemetry device within the capsule during swallowing/ingestion is unusable for any other purpose when the telemetry device is extended. Therefore the Lambert et al capsule is not space-efficient. This is a serious drawback when considering the requirement for the capsule to be as small as possible to aid ingestion.
Also the Lambert et al disclosure details the use of a high frequency (>100 MHz) radio transmitter for remotely triggering the release of the substance from the capsule into the GI tract. The use of such high frequencies is associated with disadvantages, as follows:
When power is transmitted to the capsule whilst it is inside the GI tract the energy must pass through the tissue of the mammal that has swallowed the capsule. The transmission of this power through the body of the mammal may result in possible interactions with the tissue which at some power levels may lead to potential damage to that tissue.
The higher the frequency of energy transmission the higher the coupled power for a given field strength. However, as the frequency is increased the absorption of the energy by the body tissue also increases. The guidelines for the exposure of humans to static and time varying electromagnetic fields and radiation for the UK are given in the National Radiological Protection Board (NRPB) publication “Occupational Exposure to Electromagnetic fields: Practical Application of NRPB Guidance” NRPB-R301. This describes two mechanisms of interaction: induced currents and direct heating measured in terms of the SAR (specific energy absorption rate). In general terms the induced current dominates up to 2 MHz above which the SAR effects take over.
SUMMARY OF THE INVENTION
An ingestible device for delivering a substance to a chosen location in the GI tract of a mammal includes a receiver of electromagnetic radiation for powering an openable part of the device to an opened position for dispensing of the substance. The receiver includes a coiled wire that couples the energy field, the wire having an air or ferrite core.
In a further embodiment the invention includes an apparatus for generating the electromagnetic radiation, the apparatus including one or more pairs of field coils supported in a housing.
The device optionally includes a latch defined by a heating resistor and a fusible restraint. The device may also include a flexible member that may serve one or both the functions of activating a transmitter circuit to indicate dispensing of the substance; and restraining of a piston used for expelling the substance.
According to a first aspect of the invention, there is provided an ingestible device for delivering a substance to a chosen or identifiable location in the alimentary canal of a human or animal, comprising an openable reservoir, for the substance, that is sealable against leakage of the substance; an actuator mechanism for opening the reservoir; an energy source, operatively connected for powering the actuator mechanism; a releasable latch for controllably switching the application of power to the actuator from the energy source; and a receiver of electromagnetic radiation, for operating the latch when the receiver detects radiation within a predetermined characteristic range, the receiver including an air core having coiled therearound a wire; characterised in that the coiled wire lies on or is embedded in an outer wall of the device.
This arrangement advantageously permits the use of an oscillating magnetic field as an external energy source for remotely triggering e.g. the release of a compound from the capsule. For reasons discussed below, a magnetic field offers advantages over a field including radio waves.
Preferably the housing defined ingestible device for delivering a substance to a chosen or indentifiable location in the alimentary canal of a human or animal, comprising an openable reservoir, an actuator mechanism, an energy source, a releasable latch and a receiver of electromagnetic radiation is cylindrical. Other, non-circular section housings e.g. polygonal cross sections are possible.
Preferably the dimensions of the coil are in the range of 8-12 mm and its length is in the range of 10-20 mm. Such dimensions advantageously permit the coil to form part of a capsule whose exterior is smooth and appropriately shaped and sized for ready ingestion. The use of an antenna as claimed is believed to obviate at least some of the space-inefficiency disadvantages of the Lambert et al capsule.
According to a second aspect of the invention there is provided an ingestible device delivering a substance to a chosen or identifiable location in the alimentary canal of a human or animal, comprising an openable reservoir, for the substance, that is sealable against leakage of the substance; an actuator mechanism for opening the reservoir; an energy source, operatively connected for powering the actuator mechanism; a releasable latch for controllably sw
Hirst Peter H.
Houzego Peter J.
Morgan Peter N.
Westland Duncan J.
Wilding Ian R.
Holland & Knight LLP
Mendez Manuel
Phaeton Research Ltd.
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