Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1999-05-13
2004-08-31
Page, Thurman K. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C118S013000, C118S015000, C118S020000, C118S035000, C118S037000, C118S106000, C118S123000, C118S621000, C424S439000, C427S154000, C427S289000, C427S355000, C427S372200, C427S375000, C427S458000, C427S470000, C427S472000, C427S474000, C427S475000, C427S482000, C427S487000
Reexamination Certificate
active
06783768
ABSTRACT:
The present invention relates to methods of coating by substrates, to apparatus for coating substrates and to coated substrates for pharmaceutical use. In particular, but not exclusively, the invention relates to the coating of pharmaceutical substrates to produce solid dosage forms.
BACKGROUND OF THE INVENTION
It is to be understood that the term “solid dosage form” is to be interpreted in a broad sense as covering a wide variety of pharmaceutical products. Thus the term covers pharmaceutical products to be taken orally, for example, pharmaceutical tablets of conventional shape as well as capsules and spherules and tablets of unconventional shape. The term also covers pharmaceutical products not taken orally, for example, a pessary, a bougie, a suppository or a patch for application to the skin. Also, where reference is made to “pharmaceutical substrate” it is to be understood that the term covers the substrates of the solid dosage forms indicated above. The term “solid dosage form” does not, however, include pharmaceutical products such as small pellets and granules, for example small pellets which are filled into capsule shells for administration and granules which are compressed to form tablets; such pellets or granules are not themselves each solid dosage forms but rather, when combined together in a capsule or tablet, define in combination a solid dosage form.
It will be understood that the term “active material” and “active component” used throughout the specification includes material which is biologically active and will comprise one or a mixture of pharmaceutical materials. The pharmaceutical materials include those materials which are administered for the prevention and/or treatment of disease.
Active materials are conventionally administered in the form of tablets.
In a conventional method of producing a pharmaceutical tablet, a mixture containing the biologically active ingredient together with diluents such as lactose and other ingredients is mixed and portions of the mixture are formed into discrete tablets by, for example, pressing samples of the mixture.
A problem with the method of producing tablets described above is that, due to inhomogeneity of the mixture from which the tablet cores are made, the amount of active ingredient in the resulting tablet cores varies from one tablet to the next. While that is a problem for all types of tablet core produced in that way, it is a particularly serious problem when the amount of active ingredient in each core is low, for example for active compounds of high activity. In that case a small absolute variation in the percentage amount of active ingredient in the cores corresponds to a significant variation in the dose contained in each tablet which is clearly most undesirable.
In one known method, a coating solution containing active material is applied to the surfaces of small beads using conventional spray coating techniques, for example by spraying the coating solution towards the beads as they are tumbled in a revolving drum. The coated beads are filled into capsule shells for administration. Such a method is not appropriate for use where accuracy in the amount of the active material applied to the cores is required because there is little control over the amount of coating material applied to each core using that method.
Active components are often administered in tablet form. As indicated above, conventional tablets include a small amount of active component and a large amount of diluent such as lactose so that the tablet is a convenient size. The tablet is a convenient way for the active component to be administered because each tablet contains a predetermined metered dose of the active material.
However, some patients find the taking of tablets difficult, for example because of their size or because of the presence of the other ingredients in the tablet composition. Thus an alternative dosage form would be desirable.
GB 1 561 100 describes the coating of a web with material containing an active ingredient. The coated web is processed to internalize the active coating by, for example, lamination and winding to provide a dosage form.
It is an object of the invention to overcome or mitigate one or more of the above mentioned disadvantages.
In accordance with the invention, there is provided a method of coating a substrate, the method including the steps of applying an active coating material to the substrate to form an active coating layer, the active coating material comprising biologically active material, wherein the active coating layer is removable from the substrate.
In accordance with the invention, the active material is applied as a coating to a substrate from which it can be removed.
In one alternative embodiment of the invention, the coating material is applied directly onto a surface of the coating apparatus, the coating formed in the process being removed from the apparatus as a wafer containing the active material.
In a second alternative embodiment of the invention, the coating material is applied onto a substrate, the coating being removed from the substrate as a wafer, for example by a patient prior to the administration of the material. The substrate may be, for example, a sheet comprising plastics material, for example low adhesion plastics material.
The surface of the substrate may be precoated with one or more coating layers.
Preferably, the active coating material is applied electrostatically. There are various advantages in applying coating materials electrostatically, for example, reduction in waste of coating material, improved coating efficiency and improved coating weight uniformity.
In one alternative of the invention, the active coating material is applied in the form of a dry powder.
Advantageously, at least 90% by weight of the particles of the active coating material have a particle size less than 200 &mgr;m.
Advantageously, at least 90% by weight of the particles of the active coating material have a particle size between from 1 to 200 &mgr;m. Preferably, at least 90% by weight of the particles of the active coating material have a particle size between from 1 &mgr;m to 100 &mgr;m. The term “particle size” refers to the equivalent particle diameter of the particles and may be measured using, for example, laser light diffraction. The particle size of the powder is an important factor in powder coating techniques. If the particles of the powder are very small, the powder will often be too cohesive for successful powder application using many powder coating techniques. However, large particles can be disadvantageous because they are often more difficult to coat onto a surface and, if the coating material is to be fused after application to the surface, longer fusing times may be required, leading to increased risk of damage to the substrate and to the active component.
Where reference is made to by weight of particles, for example the by weight of particles having a particular size, the particles will also preferably have that by volume of particles of that size.
Alternatively, the coating material may be applied in the form of a liquid.
Advantageously, the active coating material further includes one or more excipients. The formulation will usually consist of the active component and a mixture of excipients that will aid in the coating of the material. The formulation may also include other components, for example, colorants and/or flavourings and/or agents to control the rate of release of the active component.
Advantageously, the substrate is conveyed through a region adjacent to a source of the active coating material. That allows the method to be continuous.
In one advantageous embodiment of the invention, the method comprises supporting the substrate adjacent to the source of the active coating material with a surface of the substrate maintained at such a different electric potential from that of the active coating material that the application of the electric potential causes the active coating material to move from the source of the active coating material towards the substrate
Brown Steven R.
Reeves Linda A.
Staniforth John N.
Choi Frank
Nixon & Vanderhye
Page Thurman K.
Phoqus Pharmaceuticals Limited
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