Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Patent
1999-07-15
2000-07-11
Azpuru, Carlos A.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
424425, 424426, A61F 200
Patent
active
060869089
DESCRIPTION:
BRIEF SUMMARY
The invention relates to novel implants for the release of pharmaceutical substance. These allow the same pharmaceutical substance to be released in two or more phases or two or more pharmaceutical substances to be released in a chronologically predetermined sequence. The implants consist of layers of biodegradable polymers which erode completely within a few weeks in the body.
Research in the field of controlled release of pharmaceutical substance originally concentrated on releasing pharmaceutical substances at a constant rate in order to achieve constant plasma or tissue levels. However, it was recognized that the discontinuous release of pharmaceutical substances can also be very advantageous. By this means, for example, the development of tolerances can be prevented and in immunization higher immune responses can be achieved. A further field of application for pharmaceutical forms having discontinuous release is tumour therapy. Tumour cells tend to develop resistances if the same active compound is administered continuously. Implants which release pharmaceutical substances discontinuously or sequentially could counteract this development. An example of the potential use of such implants is the treatment of tumours in the area of the central nervous system. It is therefore desirable to have available locally implantable pharmaceutical release systems which make possible a phasewise release of different pharmaceutical substances or the same pharmaceutical substance at different concentrations.
It has now been found that implants having a multilayer structure of pharmaceutical substance-containing layers allow a phasewise release of pharmaceutical substance if the pharmaceutical substance-containing areas of these implants consist of surface-eroding biodegradable polymer materials.
The invention thus relates to implants with phasewise release of pharmaceutical substance, which consist of a core and layers arranged concentrically around it, the core and at least one of the layers comprising different pharmaceutical substances or the same pharmaceutical substance in different doses, which are characterized in that the pharmaceutical substance-containing areas of the implants consist of surface-eroding biodegradable polymer materials.
The implants according to the invention consist of a core and one or more layers of surface-eroding biodegradable polymer materials arranged around it concentrically, which can have different erosion rates.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the schematic structure of a two-layer implant in cross-section. The core 1 is surrounded by a coating layer 2. Core 1 and coating layer 2 consist of surface-eroding biodegradable polymer materials and contain the respective pharmaceutical substance.
FIG. 2 shows the schematic structure of a four-layer implant in cross-section. Here, a core 1 is surrounded by two intermediate layers 2 and 3. A jacket layer 4 is arranged around them. Core 1 and jacket layer 4 consist of surface-eroding biodegradable polymer materials and contain the respective pharmaceutical substance. The intermediate layers 2 and 3 likewise consist of biodegradable polymer materials and are free of pharmaceutical substance.
FIG. 3 shows the release from implants, in which first Carboxyfluorescein and then Brilliant Blue are released.
FIG. 4 shows the release of Brilliant blue from implants having a core 1 and layers 2, 3, and 4 as shown in Example 2.
In the simplest embodiment according to FIG. 1, the implant consists of a pharmaceutical substance-containing core and a pharmaceutical substance-containing coating layer. By appropriate choice of the polymer materials, whose biodegradability in the body is surface erosion-controlled, it is guaranteed that the respective pharmaceutical substance is released phasewise exclusively from the surface corresponding to the degradation of the polymer material. The chronological duration and the release profile can be controlled by selection of the polymer materials according to differing degradability. Depending on the
REFERENCES:
patent: 4450150 (1984-05-01), Sidman
Achim Goepferich
Azpuru Carlos A.
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