Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2000-12-21
2003-08-12
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S405000
Reexamination Certificate
active
06605289
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved stannous fluoride composition for the treatment of epidermal irritations and infections.
BACKGROUND OF THE INVENTION
Stannous fluoride has been used in dentistry since the 1950's to prevent dental cavities. Norman Tinanoff outlines 40 years of human and animal studies with some studies having greater efficacy than others in “Review of the Antimicrobial Action of Stannous Fluoride” (The Journal of Clinical Dentistry Vol. II 1990). U.S. Pat. No. 4,097,590 “Methods and Compositions for Treatment of Bacteria and Fungus infections of the skin” discloses treatment for vulgaris and athletes foot with a soluble fluoride salt. The present inventor previously determined that stannous fluoride can be used for treating diseases having viral etiology. (U.S. Pat. No. 5,098,716 to Embro).
Both the shelf life and antimicrobial effect of a stannous fluoride product depend on stability of the active stannous ion (Sn+2). Products formulated for home use achieve stability of the stannous ion by adding glycerin or other water-insoluble materials to reduce hydrolysis and oxidation. Aqueous formulations employed chelating agents which bind stannous fluoride and create a stannous reservoir that acts both as a supply of stannous ions and an antioxidant. Majeti et. al. (U.S. Pat. No. 5,004,597), developed a dentifrice stabilization system for stannous fluoride by utilizing stannous chloride as an antioxidant with stannous reservoir and sodium gluconate as a chelating agent to protect stannous fluoride from hydrolysis. Other chemicals used in stannous fluoride stabilization include polyvinyl alcohol (PVA), tripolyphosphates, copolymers of vinyl-methylether and maleic anhydride. However, the use of these and other complexing agents for stannous fluoride stabilization can limit the bioavailability of stannous ions for a therapeutic effect.
In view of the foregoing, there is a need to provide improved stannous fluoride compositions.
SUMMARY OF THE INVENTION
The present invention relates to an improved stannous fluoride composition comprising stannous fluoride and at least one zinc containing compound. The inventor has shown that the improved composition is more stable and less toxic than a stannous fluoride composition that does not contain a zinc compound. The inventor has also shown that the improved composition of the invention allows one to decrease the dose of stannous fluoride required to achieve a therapeutic effect.
The inventor has demonstrated that the improved composition of the invention is effective in treating epidermal irritations and infections and their symptoms. Accordingly, the present invention also provides a method of treating an epidermal irritation or infection comprising administering an effective amount of a composition comprising stannous fluoride and at least one zinc containing compound to an animal in need thereof.
Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
DETAILED DESCRIPTION OF THE INVENTION COMPOSITIONS OF THE INVENTION
The present invention relates to an improved stannous fluoride composition comprising stannous fluoride and at least one zinc containing compound. This composition may be referred to herein as “the composition of the invention”.
The composition of the invention is markedly improved over a composition containing stannous fluoride without any zinc compounds in several respects. Firstly, stannous fluoride undergoes hydrolysis and oxidation in aqueous environments which results in the loss of stannous bioavailability due to the precipitation of stannous hydroxide. The zinc containing compounds stabilize the stannous fluoride by preventing the oxidation and hydrolysis of the stannous ion. Zinc ions have a greater affinity than stannous ions for hydroxides and other anions in aqueous solutions. As a result the zinc in the composition of the invention will complex the hydroxides and inhibit hydrolysis and precipitation of the stannous ions. In particular, the inventor has demonstrated that a stannous fluoride solution containing zinc gluconate remained stable, without precipitation, for at least 3 months. In contrast, a stannous fluoride solution without zinc gluconate extensively precipitated. Secondly, the zinc compounds buffer the hydrogen ion which promotes an elevated pH. This makes the composition more suitable for topical use as more acidic formulations can irritate or cause a burning sensation of the skin. Thirdly, the present inventor has unexpectedly found that the zinc compounds act synergistically with and potentiate the activity of the stannous fluoride. In particular, the present inventor has demonstrated that in the composition of the invention the stannous fluoride works better than when twice the dose is used in a composition that does not contain the zinc compounds. Consequently, the dose of the stannous fluoride can be significantly lowered in the composition of the invention resulting in a less toxic composition.
As mentioned above, inclusion of zinc compounds in the composition of the present invention stabilizes and enhances the efficacy of the stannous fluoride. Using zinc containing compounds in the composition also has additional advantages in that zinc is widely recognized as having medicinal and healing properties. In particular, 1) zinc is essential for life; 2) zinc is necessary for over 100 enzymes (i.e., alcohol dehydrogenase carboxypeptidase); 3) zinc maintains body levels of Vitamin A; 4) zinc is important in sex organ function and reproduction; 5) zinc is important for DNA/RNA synthesis; 6) zinc can improve cell-mediated immunity; and 7) zinc is incorporated in hundreds of dermatological formulas to help maintain healthy skin cells. Using stannous compounds with the stannous fluoride will not provide the added benefits that zinc does as stannous is not essential for life and is not necessary for enzyme function.
The zinc containing compound can be any compound containing zinc including zinc carboxylates and zinc salts. The zinc carboxylate is preferably selected from one or more of zinc gluconate, zinc tartrate, zinc malate, zinc propionate, zinc citrate and zinc acetate. More preferably, the zinc carboxylate is zinc gluconate. The zinc salt is preferably selected from zinc chloride, zinc sulfate, zinc phosphate, zinc pyrophosphate, zinc oxide or zinc thiocynate. Preferably, the zinc salt is zinc chloride.
The composition of the invention preferably comprises stannous fluoride in a concentration ranging from about 0.01 wt % to about 10.0 wt % and one or more zinc containing compound in an amount from about 0.05 wt % to about 20.0 wt %.
In a preferred embodiment, the composition comprises stannous fluoride and zinc gluconate. The inventor has shown that a composition comprising stannous fluoride and zinc gluconate provides significantly greater efficacy in the treatment of a viral, bacterial and fungal infections as compared to a stannous fluoride composition alone. In particular, the inventor has demonstrated that with the improved composition one can use one half the amount of stannous fluoride as is used in a composition containing stannous fluoride alone with improved results.
Preferably, the stannous fluoride is provided in a concentration ranging from about 0.1 wt. % to about 8.0 wt. % and zinc gluconate is provided in concentration ranging from about 0.5 wt. % to about 10.0 wt. %. Most preferably, the composition comprises 0.20 % stannous fluoride and 1.5% zinc gluconate, in a non-aqueous medium such as glycerin.
The composition may additionally contain zinc chloride in a concentration ranging from about 0.5 wt. % to about 5.0 wt.
Embro Research Company, LLC.
Fulbright & Jaworski L.L.P.
Page Thurman K.
Ware Todd D
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