Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Capsules
Patent
1997-06-05
1999-09-28
Levy, Neil S.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Capsules
424456, 424485, A61K 0948
Patent
active
059584505
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
THIS INVENTION relates to a method of drug delivery and coated oral dosage forms such as capsules for use in the method.
BACKGROUND OF THE INVENTION
In order to deliver drugs which may include medicines, vitamins and other substances directly to the intestines by oral means, such active substances are usually coated with gelatin based materials such as capsules or caplets. This is due to the fact that if such substances are not coated with a protective coating, such substances would be broken down in the highly acidic environment of the stomach.
Capsules are usually made in rigid or soft form wherein powders or granules of a drug or other active ingredient are enclosed in a rigid gelatin shell or in soft gelatin shell which soft shell may also contain glycerol as well as gelatin to maintain plasticity of the outer shell. Powder semi-solids or liquids that do not soften or dissolve the gelatin shell can be enclosed. Powder and semi-solids can be encapsulated in a two part shell i.e. cap and body whereas liquids may be encapsulated in a capsule that is formed, fitted and heat sealed all in one operation using especially designed apparatus.
In addition to inert polymers that control drug diffusion, polymers can be designed to dissolve, swell, or degrade in a controlled manner, thereby releasing the incorporated drug. It is, however, necessary that the polymer be transformed into a water-soluble product that evokes no limiting toxic response if the spent product is not to be reclaimed. The drug is locked into a polymer matrix (i.e. a drug reservoir) before its transformation. The surface area of the polymer-drug mass, the drug concentration and solubility characteristics, and the rate of polymer transformation affect the rate at which the drug is delivered. The polymer structure undergoes a phase change during which it or its by-products are removed or eliminated from the body, either during drug release or when most of the drug is deployed.
The polymers investigated for such systems include polyesters, polyorthoesters, polyacids, hydrogels, celluloses, polypeptides, polyaminotriazoles, and albumin beads. Therapeutic agents investigated for delivery from polymeric matrices include narcotic antagonists (naloxone), steroids, antimalarials, insulin, enzymes, antibacterials, ophthalmic agents, vitamins and anticarcinogens.
Encapsulation with liposomes promotes the passage of drugs across cell-membrane barriers, prolongs plasma lifetime of drugs with short biological half-lives, and directs drug disposition. The aqueous compartments bounded by bimolecular lipid layers carry the drug-containing platform closer to the target site, thus providing higher concentrations than the usual systemic therapy. The quantity of the drug or agent administered can, therefore, be reduced considerably.
Active ingredients which are required to be released in different parts of the alimentary tract may be coated or packaged in materials which react differently with body fluids having varying pH values in different parts of the alimentary tract.
Coatings which resist the action of gastric acids but dissolve under the less acidic conditions in the duodenum and intestines are generically known as enteric coatings and are applied to capsules as well as tablets.
Although enteric capsules have been known since the end of the 19th century their development has not paralleled that of enteric-coated tablets. This has been mainly due to the difficulties in making enteric capsules completely resistant to gastric acids.
Gelatin-based capsules, however, may be made acid resistant by treating them with formaldehyde. This process has a disadvantage in that the chemical cross linkage changes to the gelatin as a result of the formaldehyde treatment can continue during a storage period resulting in an undesirable hardening of the capsules.
Furthermore, trace amounts of formaldehyde in foods and pharmaceuticals because of the toxic properties of this substance also raises problems with food and drug administration authorities.
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Behrens et al Tropical Doctor vol. 22 No. 3 pp. 107-108 1992.
News Release Aug. 21, 1987 p.1 Bepex Introduces New Food Grade Sodium Alginates.
Derwent Abstract No. 89-228916, JP 01-228916, "Seaweed-Filled Sheet", Satomitsu Kitamura, dated Sep. 12, 1989.
Levy Neil S.
Phillip Peatey & Gunter Pauli
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