Drug – bio-affecting and body treating compositions – Anti-perspirants or perspiration deodorants
Reexamination Certificate
2002-09-16
2003-11-18
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Anti-perspirants or perspiration deodorants
C424S066000, C424S068000, C424S400000, C424S401000
Reexamination Certificate
active
06649153
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a novel skin friendly antiperspirant composition in which the modifying component comprises a polyhydric alcohol, preferably glycerin, is substantially complexed within the antiperspirant. The invention is applicable to the types of activated or nonactivated aluminum or aluminum/zirconium salts that are commonly considered antiperspirant active materials and are covered by FDA OTC Tentative Final Monograph as Category I.
It is desirable for an antiperspirant product to provide aesthetics (pleasing skin feel) in addition to excellent antiperspirancy. Appearance and feel of the skin is a major concern to the consumer as well as to the cosmetic industry. In order to understand how to control skin feel and appearance it is necessary to gain a better understanding of biological/biophysical factors affecting stratum corneum (SC), the outermost layer of the skin.
The structure and function of the stratum corneum has been the subject of intensive investigation over the past three decades. Its structure in the published literature of L. D. Rheim, etal, “Development of Stratum Corneum Lipid Model to Study the Cutaneous Moisture Barrier Properties” Colloids and Surfaces, 48 (1990) 1-11 Elseiver Science Publishers, has been likened to brick wall, with the bricks representing corneocytes themselves and the ‘mortar’ representing the highly specialized intercellular lipids. The intercellular lipids are composed primarily of ceramides, cholesterol and fatty acids together with smaller amounts of phospholipids and glucosylceramides. These lipids form the major permeability barrier to the loss of water from the underlying epidermis and also from the part of the intercellular cement which helps to maintain the integrity of the tissue.
Human stratum corneum contains 15 such corneocyte/lipid layers. The corneocytes contain mainly the structural protein keratin.
A major function of the stratum corneum is to provide a barrier to evaporation of water. If this layer is removed from the skin e.g., by tape stripping, a fifty (50) fold increase in the rate of water loss ensues. Moisturization capacity of the SC is a major concern to the cosmetic industry since consumers are highly concerned about dry skin and moisture replenishment. Additionally dry skin can result in increased incidence of cuts during shaving.
The intercellular lipids are thought to play a major role in preventing water loss through the stratum corneum. To better understand the barrier function of the intercellular lipids and their role in regulating moisture loss from skin, numerous researchers are probing the structural organization of stratum corneum lipids and trying to understand what is the mechanism through which polyols and especially glycerin, mediate its effect on alleviating skin xerosis in vivo.
It has been shown that glycerin does not exhibit humectant properties at or below 6% RH (relative humidity) that is, neat glycerin samples exposed to 6% RH did not gain water over time. Thus, in low relative humidity climates it is unlikely that glycerin improves dry skin by humectancy. Rheim, et al. found that by incorporating glycerin into lipid model (at 10% levels) it prevented the formation of solid crystals and maintained a largely liquid crystalline state for the lipid/glycerin system. It was therefore concluded that in dry atmosphere glycerin may act as a moisturizer by inhibiting the lipid phase transitions from liquid to solid crystals. Maintaining the lipid in a liquid crystalline state with only small amounts of solid crystals may be the key for optimal barrier function.
Using in vitro stratum corneum extensibility model, Rawling, et al (“The effect of glycerol and humidity on desmosome degradation in stratum corneum”, Arch. Dermatol Res. 1995 287: 437-464) have consistently found glycerin to be superior to all other humectants and polyols in skin xerosis and their effect of inhibiting lipid crystallinity.
It has also been reported that enzymatic activity, and thereby desmosome degradation occurs only above a certain water content in the stratum corneum. When the stratum corneum lipid structure is disturbed, the resulting reduction in stratum corneum hydration leads to the retention of corneocytes on the skin's surface and the manifestation of skin xerosis due to reduced desmosome degradation. If, therefore, stratum corneum moisturization and water barrier function can be restarted by the topical use of a suitable moisturizer, the desquamatory process can be restored by the topical use of an ideal moisturizer and xeratic skin conditions may be treated more effectively. One compound that meets all these requirements is glycerin. The action of glycerin has been explained in terms of its occlusive, humectant and lipid phase modulating properties, all of which translate into moisturization and barrier improvements for the stratum corneum. More recently, it has been shown that glycerin aids enzyme layers of desmosomes in the stratum corneum. All of this represents an alternate, more likely molecular mechanism of action for skin moisturizing by glycerin.
Glycerin is not the only material that has been shown to condition the skin without hydrating it. The effects of another nonhygroscopic skin softener, a modified triglyceride known as glyceridacid was reported by R. S. Summers, et al, “The effect of lipids, with and without humectant, on skin xerosis. J. Soc. Cosmetic Chemist Vol. 47; 27-39”, as exerting skin softening effects via interaction with the stratum corneum lipids. Recently another class of compounds known as &agr; hydroxyacids have been investigated and these compounds which, are non humectants have been found to plasticize the stratum corneum even under conditions of low relative humidity (20% RH). Fraebe, et al , “Prevention of Stratum Corneum lipid phase transitions in vitro by glycerol—an alternative mechanism for skin moisturization”. J. Mattai, J. Soc. Cosmetic Chemist Vol. 41, 51-65 reported that &agr; hydroxy acids, particularly the longer chains (C
10
, C
12
) species may enable these compounds to penetrate the fatty acid chains of the bilayer, interrupting the close packing of these chains and thereby enhancing the fluidity of the membrane.
As pointed out by P. Thau (“Glycerin Current Insights into the Functional Properties of Classic Cosmetic Raw Material”, J. Cosmetic Sci. Vol. 53, 229-236”) studies conducted within the past twenty to twenty five years have enabled us to gain significant understanding of the complex interactions of glycerin with the epidermis. Results of these studies in the form of interaction of glycerin with the epidermis are listed below.
1. increases the extensibility of the stratum corneum
2. increases the water gradient in the skin
3. reduces surface roughness (may not be caused solely by moisturization)
4. penetrates into the phospholipid bilayers
5. maintains the intercellular lipid cement in a fluid liquid crystal state, particularly under conditions of low temperature and low RH
6. accelerates recovery of barrier function in vivo
7. serves to accelerate wound healing
8. aids in the digestion of desmosomes
9. provides a skin protection function
10. enhances corneocyte desquamation
11. does not interfere with biochemical processes in the skin
The preservation of skin structure and function with concomittant mildness and metabolic inactivity truly makes glycerin the quintessential cosmetic ingredient. However, blending of glycerin with antiperspirant powder (basic aluminum halides, nitrate, or aluminum/zirconium complexes as identified in OTC monograph) in a typical antiperspirant stick formulation results in agglomeration and formation of gritty particles requiring use of flow enhancers such as silica and talc. In general, colloidal silica in amounts up to about 1% by weight by the total composition and preferably about 0.05 to 0.5% is used. However, silica and talc present dusting and health related problems and the finished product does not provide excellent skin feel as they tend to increase drag.
Besides health concer
Li Zijun
Parekh Jawahar C.
Dodson Shelley A.
Plantamura Arthur J.
Reheis Inc.
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