Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Tablets – lozenges – or pills
Reexamination Certificate
1999-07-27
2001-05-29
Spear, James M. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Tablets, lozenges, or pills
C424S468000, C424S469000, C424S474000
Reexamination Certificate
active
06238698
ABSTRACT:
The invention relates to an oral preparation, comprising at least one pharmaceutical active compound in a matrix which is swellable in aqueous medium, which is released from the matrix into the aqueous medium in a delayed manner, while the matrix remains largely resistant to disintegration.
The delayed release of active compound from oral administration forms serves to avoid undesired plasma level variations. The construction variants with which delayed active compound release can be achieved also include layered tablets, in particular those in which the surface of the active compound-containing layer enlarges in the course of the release, whereby the release rate can be controlled in such a way that it remains largely constant. Depending on the design and the formulation of the layered tablet, this surface layer enlargement can result from the continuous erosion of one or more adjacent layers or from the swelling of the active compound-containing layer. The first-mentioned principle was described in the documents P 43 41 442.7 and P 44 16 926.4, the second, for example, in U.S. Pat. No. 5,422,123.
In the study of commercially available layered tablets having a swellable matrix layer, it was recognized as essential that a satisfactory surface enlargement due to swelling can only be achieved if mechanical stress on the tablet is largely avoided. If, to be precise, swelling takes place on entry of aqueous medium, a semi-solid gel of comparatively low mechanical stability results with increase in volume. Even the carrying-out of the disintegration test according to GP 10 using applied Plexiglass discs leads to a serious loss of shape of the swollen tablets.
The cause of the lack of mechanical stability of such matrix layers in the swollen state is the use of swellable polymers producing a swelling. They are mainly strongly hydrophilic polymers which, however, are insoluble or slowly soluble due to crosslinking, due to formation of crystalline fields or due to their large chain length. Examples of these types of polymers are croscarmellose, polyvinyl alcohol with a high degree of hydrolysis and high molecular weight hydroxypropylmethylcellulose. These very highly swellable polymers are also employed as disintegration accelerators or disintegrant in tablet formulations on account of this property (Sucker et. al., Pharmazeutische Technologie, Thieme Verlag, 1991, pp 174 et seq.). The preparation of swellable matrices which simultaneously remain mechanically stable when adequately swollen in aqueous medium is extremely problematical using the polymers mentioned, since their swelling-promoting properties cannot be separated from disintegration-promoting properties.
REFERENCES:
patent: 5422123 (1995-06-01), Conte et al.
patent: 5603956 (1997-02-01), Mateescu et al.
patent: 43 41 442 C2 (1993-12-01), None
patent: 44 16 926 A1 (1994-05-01), None
patent: 94 02121 (1994-02-01), None
patent: 94 21236 (1994-09-01), None
patent: 0795 324 A2 (1997-09-01), None
Lenaerts, et al., “Controlled Release of Theophylline from cross-linked amylose tablets”,Journ. Of Controlled Release1991 15; 39-46.
Sucker, Fuchs and Speiser,Pharm. Techn.2, Auflage Jan. 1991.
Jordan and Hamburg LLP
LTS Lohmann Therapie-Systeme GmbH
Spear James M.
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