Stabilized pseudo-emulsions and their preparation process

Details Stabilized pseudo-emulsions and their preparation process Stabilized pseudo-emulsions and their preparation process

1997-11-21

2000-04-25

Dodson, Shelley A.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

424 59, 424 7803, 514777, 514781, 514786, 514787, 514844, 514937, A61K 700, A61K 742, A61K 3174, A61K 4700

Patent

active

060541385

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to new formulations of heterogeneous galenic compositions which can be employed especially in dermatology and in cosmetology.
Heterogeneous galenic forms constitute the ultimate degree of complexity, because of the presence of compounds which are both lipophilic and hydrophilic: their purpose is to clean, treat, protect and beautify the skin with concern for the care, comfort and pleasure of the user.
The art of galenics has always found its letters patent of nobility in the production of emulsions.
This art has essentially always consisted of the research and/or the development of emulsifying or surface-active substances which can produce a stable suspension of oil and water, which are renowned for being immiscible.
These emulsifiers are always of various origins: synthetic for the most part or natural, such as, for example, lecithins.
Regardless of their origins and of the strength of their emulsifying power, the part played by an emulsifier can be likened to that of the detergents which are known for their reactivity both on textile fibers and on cutaneous tissues.
For reasons of industrial manufacture and of physical stabilities in time, all cosmetic emulsions contain emulsifiers the nature of which may be nonionic (e.g. optionally oxyethylenated derivatives of sorbitol, sucrose derivatives), anionic (fatty acid salts) or cationic (quaternary ammonium derivatives) nevertheless the least frequently employed because they are classed among the most reactive and more recently emulsifying polymers known by the name of Pemulen.RTM..
However, even when chosen among the best ones, these emulsifiers remain dangerous to the skin for a number of reasons.
The skin is covered with a protective film, called hydrolipid surface film (HLSF) and consisting predominantly of fatty substances excreted by the sebaceous glands and of lipids originating from the degradation of the cells during the keratinization phase of the corneous cells.
When spread onto the skin, the emulsion is dissociated and the outer aqueous phase evaporates off leaving in place the emulsifier which exhibits an affinity for the oils or fatty substances of the (HLSF); it thus facilitates the subsequent removal of this film from the surface of the epidermis.
This film will thus be impoverished day after day. Only fatty skins, extensively provided with sebumsecreting sebaceous glands will be able to compensate for this destruction. However, the phenomenon of reactional seborrhoea is nevertheless known, caused by the use of surfactants which are too reactive for daily cleaning.
As for dry skins, these are already disadvantaged by a deficient HLSF.
In addition, the lipid cement binding the corneous cells is disorganized and no longer plays its part as a barrier and on some categories of weakened skins known as sensitive, elderly people, atopic young children, some reactions will be able to occur more easily.
It is known, furthermore, that the impoverishment of this barrier effect increases the frequency of so-called orthoergic irritant reactions and that the repeated application of products on skin of this type can in the long term result in reactions of sensitization to one of the constituents--so-called allergic reactions.
In addition, emulsifiers act as adjuvants of transcutaneous entry; as such, they reveal the irritant or allergy-inducing effect of various other substances present in the formulation, which would be completely tolerated in their absence.
They have a cytotoxic effect in vitro in cell culture. This toxicity illustrates the direct action which some emulsifiers can exert according to their--nature and their concentration--on epidermic cells devoid of their weakened natural protection and then finally smoothed down because of the gradual damage suffered by the cytoplasmic membrane.
All the present emulsions contain emulsifiers in application of a fundamental principle of formulation which is definitively accepted; the formulator's role therefore consists in choosing an emulsifier and in determining its concentr

REFERENCES:
patent: 4963656 (1990-10-01), Mitani
patent: 5075113 (1991-12-01), DuBois
patent: 5478555 (1995-12-01), Bara et al.
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patent: 5833951 (1998-11-01), Atrz et al.
patent: 5874092 (1999-02-01), Roulier et al.
The Merck Index, p. 5452 and 5453 at 5452 Lecithin, 1996.

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