Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1993-11-02
1998-10-27
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
424 7817, 424 7818, 424 7827, 5153328, 5153329, 5153331, 5153332, 515342, 515379, C08F 800
Patent
active
058279253
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to oral drug delivery systems for site specific drug delivery. More particularly, the present invention relates to drug delivery systems wherein a drug is covalently bound to a polymeric material for site specific delivery of the drug based upon the pH of the site wherein the drug is to be delivered. The present invention is especially directed to a delivery system for delivering a drug in an environment exhibiting a pH of up to about 7 such as can be found in the gastric system.
2. Prior Art
Various approaches are disclosed in the prior art for achieving controlled oral delivery of drugs. The majority of such approaches are directed to sustained release in vivo and utilize a polymeric material as a carrier, coating or rate-limiting barrier such as a membrane. One sustained release delivery system utilizes chemical bonds to control release. Ferruti et al, U.S. Pat. No. 4,228,152, disclose a polymeric sustained release prostaglandin delivery system wherein a prostaglandin is directly bonded or bonded through an oxyalkylenic, aminoalkylenic, or oxyaminoalkylenic chain to a polyacrylic or polymethacrylic backbone. Upon entry into the body, the prostaglandins are reported to be gradually hydrolyzed causing release thereof into the body over sustained time intervals.
Few systems, however, are directed at localized drug delivery wherein the delivery of a drug is confined to a particular tissue or organ. One such system is disclosed by Saffron, in U.S. Pat. No. 4,663,308. Saffron discloses a polymeric drug delivery system for localized drug delivery wherein a drug is coated with a polymer which is crosslinked with an azo compound. The azo bonds are reported to be reduced by azo reductases existing in the large intestine causing the polymer coating to degrade, thereby releasing the drug into the large intestine. Another of such systems is disclosed by Siegel et al in J. Controlled Release, 8, 179-182 (1988). Siegel et al disclose hydrophobic polyamine hydrogels useful for regional drug delivery at nonneutral pH values.
SUMMARY OF THE INVENTION
The present invention is directed to localized drug delivery through oral administration of an acidic pH-dependent drug delivery system. One aspect of the subject drug delivery system involves release of a drug in an acidic environment such as in a gastric environment which typically has a pH value ranging from about 1 to about 4. In this system, the drug can be covalently bonded to the polymer backbone or to a pendant functional group on the polymer backbone and can be released from the polymer by hydrolytic cleavage of the covalent bond at a pH below about 7. The drug can be incorporated into the polymer by way of a pH-sensitive linker to which the drug can be covalently bonded which covalent bond is cleaved at pH values of less than about 7 but not at higher pH values. Thereby release of the drug at such higher pH values, such as about 7 or higher, is inhibited. In another aspect, the present drug delivery system involves methods of covalently bonding drugs to polymeric materials by way of chemical linkers, and particularly involves methods for incorporating drugs into polymers by way of acid-sensitive linkers.
In another aspect of the invention herein, the polymeric material can be adapted to swell at pH values of about 1-7 to enhance release of an effective amount of the drug. The drug can be covalently bonded to the polymer as described above through a pH-sensitive linker such that when the polymer swells upon exposure to the acid environment, the release of the drug into the gastric environment is facilitated.
More particularly, the invention herein is directed to a delivery system for releasing an active ingredient at pH values up to about 7 and for inhibiting release of the active ingredient at pH values above 7. The delivery system includes a polymeric material covalently bonded to the active ingredient through a silyl bond that is pH sensitive and capable of being cleaved at pH values
REFERENCES:
patent: 4489056 (1984-12-01), Himmelstein et al.
patent: 4764364 (1988-08-01), Heller et al.
patent: 5474767 (1995-12-01), Tremont
Collins Paul Waddell
Jones Peter Hadley
Perkins William Eldredge
Tremont Samuel J.
Lipman Bernard
Monsanto Company
Williams Roger A.
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