Surgery – Controlled release therapeutic device or system
Patent
1997-04-30
1999-11-09
Mendez, Manuel
Surgery
Controlled release therapeutic device or system
A61K 922
Patent
active
059805080
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to devices and methods for the administration of useful agents, for example bioactive agents, to humans, animals, plants, fish or birds (herein called "the patient"). It has particular, though by no means exclusive, application to the staged delivery of multiple doses of one or more agents at timed intervals over a prolonged period of time and/or to the continuous delivery of one or more agents over a prolonged period of time.
The uses of such methods, devices and capsules are many and varied. For example, controlled-release may be used to maintain the blood-level of a therapeutic agent substantially constant over an extended period of time; it may be used to achieve a predetermined time/concentration profile of an antigen in the blood, an anti-tumour agent in an organ, or an anthelmintic in the gut and/or blood of a patient; or, as required for the administration of some hormones which control reproduction or growth, and are required for the administration of many antigens (e.g. in vaccination), controlled release may be used to achieve pulsatory delivery where multiple doses of a drug are required at predetermined intervals or where an extended dose is to be delivered in a continuous or pulsatory fashion.
For convenience in this specification, the active agent to be delivered, whether it be a hormone, antibiotic, antigen, vitamin, anti-tumour drug, vaccine, cytokine, etc., will be termed a "drug", though it is by no means limited to pharmaceutical compounds, nor to the route of administration (e.g. subcutaneous, intra-muscular, sub-dermal, dermal, intravenous, intra-arterial, peritoneal, etc.).
BACKGROUND OF THE INVENTION
With the development of more and more types of extracted, synthetic or genetically engineered hormone-like substances which are effective at very low levels of concentration, the need for implantable or ingestable controlled-release capsules has grown considerably and many designs for such devices have been proposed. One convenient form of implantable device is an open-ended cylinder or tube of a few millimeters in diameter (so that it can be implanted by the use of a hypodermic syringe) formed from material which is biocompatible but generally impervious to body fluids.
If the sustained release of a single drug dose is desired, the drug is simply mixed with a suitable excipient, loaded into the device and implanted. Whereupon, the action of the body fluids gradually dissolves, disperses or penetrates the excipient and releases the drug over a period of time. If pulsatory delivery is required, the capsule cylinder may be loaded with a succession or `stack` of alternating `active` and `spacer` layers each comprising a suitable excipient, carrier or matrix. Each active layer contains a dose, or a relatively high concentration of the drug(s) to be delivered, while each spacer layer contains no drug(s) or a relatively low concentration thereof. Dissolution, leaching or erosion of each successive layer (by body fluids after implantation) provides the desired pulsatory drug delivery, while the formulation of the excipient of an active layer determines the profile of the corresponding dose, and the formulation of a spacer layer determines the time interval between the doses of the adjacent active layers.
Such known capsules may be divided into those which are `active` (or `swellable agent`) and those which are `passive` (or `un-swellable agent`). In the latter, the timing and rate of release of the drug doses represented by the active layer(s) depends upon the formulation of the excipient(s) and drug(s) employed, given a particular composition of surrounding body fluid. In the former, the layer-stack is pushed or extruded gradually from the open end of the capsule by a `swellable agent` located at the other--and closed--end of the capsule, so that one layer after another is ejected for dissolution into the body fluids. Thus, the interval between doses--and to some degree, the dose profile as well--is determined by the rate of extrusion as we
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Bentley Herbert William
Cardamone Michael
Controlled Release Technologies Pty Ltd
Mendez Manuel
Pauly Joan H.
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