Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Patent
1993-02-24
1996-04-09
Webman, Edward J.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
424461, 424456, A61K 914, A61K 962
Patent
active
055059660
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel colon selective pharmaceutical composition as well as to a process for its preparation.
The conventionally used pharmaceutical compositions for oral delivery of drugs which are to exert their activity locally in the colon are not quite satisfactory. For example, they release a considerable amount of the active component already on their way to the colon tract and/or the release of the active component is too slow once the composition has reached the colon.
The present invention aims at overcoming the deficiencies of the prior art compositions by providing an improved colon selective composition which substantially retains the drug within the composition matrix until it reaches the colon, at which time the drug is quickly and efficiently released, as well as a process for the preparation of such a composition.
According to a first basic concept of the present invention, a pharmaceutical composition for oral delivery of a therapeutically active substance has the latter dispersed in a matrix material core, at least a substantial part of which is selectively degradable by the enzymes normally occurring in the colon, thereby providing for rapid decomposition of the matrix and momentary release of the active substance(s) dispersed therein once the composition has reached the colon.
According to a second basic concept of the invention, the matrix core is provided with a protective cover layer having no therapeutically active substance dispersed therein, which protective cover layer also is selectively degradable in the colon. Such a cover layer will serve as a protective or wear layer during the transport of the composition through the gastro-intestinal tract and prevent leakage of the active substance(s) from the matrix core into the surrounding medium.
Thus, in one aspect the present invention provides a colon selective pharmaceutical composition for oral delivery of one or more therapeutically active substances, comprising (i) a matrix core having the active substance(s) dispersed therein, and (ii) an outer cover layer without any active substance dispersed therein, said matrix core and cover layer being selectively degradable by enzymes normally occurring in the colon, such that the composition substantially will retain the active substance(s) therein until it reaches the colon, when the active substance(s) will be released.
In another aspect the present invention provides a method for the preparation of such a colon selective pharmaceutical composition for oral administration, comprising the steps of (i) mixing one or more therapeutically active substances with a matrix material to prepare a matrix core having the active substance(s) dispersed therein, and coating said matrix core with a material without any active substance dispersed therein to provide the matrix core with a drug-free protective cover layer, said matrix and cover layer materials being based upon substances selectively degradable by enzymes in the colon.
While a matrix core selectively degradable by colonic enzymes will efficiently release the active substance(s) once the composition has reached the colon, the provision of a drug-free cover layer non-permeable for the active substance(s) and which is also selectively enzymatically degradable in the colon but resistant to the conditions prevailing in the stomach and small intestine, will prevent leakage of active substance from the coacervate matrix, especially if the active substance is soluble in water, and also strengthen the matrix mechanically. Such coating will thus provide for protection against both physical and chemical activity in the passage of the composition form through the upper parts of the gastro-intestinal tract.
Preferably, the matrix, and advantageously also the cover layer, are based upon one or more polysaccharides selectively degradable by enzymes in the colon. By the term "based upon" as used herein in the present context is meant that the matrix contains sufficient degradable component for the coated matrix to be efficiently di
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Arne Kristensen
Bengt Wideholt
Edman Peter
Kabi Pharmacia AB
Webman Edward J.
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