Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2000-07-26
2002-07-16
Dees, Jose′ G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S059000, C424S062000, C424S450000, C424S489000
Reexamination Certificate
active
06419938
ABSTRACT:
The present invention relates to cosmetic and dermatological emulsions, in particular skincare cosmetic and dermatological emulsions. In a preferred embodiment, the present invention relates to a use which permits the stability of electrolyte-containing preparations, in particular emulsions, preferably of O/W emulsions, to be increased.
The skin is the largest human organ. Amongst its many functions (for example for temperature regulation and as a sensory organ) the barrier function, which prevents the skin (and ultimately the entire organism) from drying out, is by far the most important. At the same time, the skin acts as a protective device against the penetration and absorption of external substances. This barrier function is effected by the epidermis, which, as the outermost layer, forms the actual protective sheath against the environment. Being about one tenth of the total thickness, it is also the thinnest layer of the skin.
The epidermis is a stratified tissue in which the outer layer, the horny layer (Stratum corneum), is the part which is of significance for the barrier function. The Elias skin model, which is currently recognized in the specialist field (P. M. Elias, Structure and Function of the Stratum Corneum Permeability Barrier,
Drug Dev. Res.
13, 1988, 97-105), describes the horny layer as a two-component system, similar to a brick wall (bricks and mortar model). In this model, the horny cells (corneocytes) correspond to the bricks, and the lipid membrane in the intercellular spaces, which is of complex composition, corresponds to the mortar. This system is essentially a physical barrier to hydrophilic substances, but, because of its narrow and multilayered structure, can equally, however, also be passed by lipophilic substances only with difficulty.
The present invention relates, in a particular embodiment, to cosmetic or pharmaceutical preparations having a reduced feel of stickiness, to processes for their preparation, and the use of active ingredients for reducing the feel of stickiness of cosmetic preparations.
Apart from its barrier action against external chemical and physical influences, the epidermal lipids also contribute to the holding together of the horny layer and have an effect on the smoothness of the skin. In contrast to the sebaceous gland lipids, which do not form a continuous film on the skin, the epidermal lipids are distributed over the entire horny layer.
The extremely complex interaction of the moisture-binding substances and of the lipids of the upper layers of the skin is very important for the regulation of skin moisture. For this reason, cosmetics generally comprise, in addition to balanced lipid mixtures and water, water-binding substances.
As well as the chemical composition, however, the physical behavour of these substances is also of importance. The development of very biocompatible emulsifiers and surfactants is therefore desirable. Products formulated therewith aid the liquid-crystalline organization of the intercellular lipids of the Stratum corneum, thereby improving the barrier properties of the horny layer. It is particularly advantageous if their molecular constituents consist of substances which are naturally occurring in the epidermis.
Cosmetic skin care primarily means that the natural function of the skin as a barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of endogenous substances (e.g. water, natural fats, electrolytes) is strengthened or rebuilt.
If this function is impaired, increased resorption of toxic or allergenic substances or attack by microorganisms may result, leading to toxic or allergic skin reactions.
Another aim of skin care is to compensate for the loss by the skin of lipids and water caused by daily washing. This is particularly important when the natural regeneration ability is insufficient. Furthermore, skincare products should protect against environmental influences, in particular against sun and wind, and delay skin ageing.
Medicinal topical compositions generally comprise one or more medicaments in an effective concentration. For the sake of simplicity, in order to distinguish clearly between cosmetic and medicinal use and corresponding products, reference is made to the legal provisions in the Federal Republic of Germany (e.g. Cosmetics Directive, Foods and Drugs Act).
Customary cosmetic forms of application are emulsions. This term generally means a heterogeneous system of two liquids which are immiscible or miscible only to a limited extent with one another, which are usually referred to as phases. One is in the form of droplets (disperse or internal phase), whilst the other liquid forms a continuous (coherent or internal) phase. Less common forms of application are multiple emulsions, i.e. those which, in the droplets of the dispersed (or discontinuous) phase, comprise for their part droplets of a further dispersed phase, e.g. W/O/W emulsions and O/W/O emulsions.
More recent findings have recently led to a better understanding of cosmetic emulsions which are of relevance in practice. Here, it is assumed that the emulsifier mixtures used in excess form lamellar liquid-crystalline phases or crystalline gel phases. In the gel network theory, stability and physicochemical properties of such emulsions are attributed to the formation of viscoelastic gel networks.
In order to be able to ensure the metastability of emulsions, interface-active substances, i.e. emulsifiers, are usually necessary. The use per se of customary cosmetic emulsifiers is entirely acceptable. Nevertheless, emulsifiers, as ultimately any chemical substance, may in certain cases cause allergic reactions or reactions based on oversensitivity of the user. For example, it is known that in some particularly sensitive people, certain light dermatoses are triggered by certain emulsifiers and simultaneous action of sunlight.
It is possible to prepare emulsifier-free preparations which, for example, have, in an aqueous phase, dispersed oil droplets, similar to an O/W emulsion. A prerequisite for this may be that the continuous aqueous phase has a gel framework which stabilizes the dispersed phase, and other conditions besides. Such systems are sometimes called hydrodispersions or oleodispersions depending on which is the disperse phase and which is the continuous phase.
For cosmetic technology, it is, however, neither necessary nor possible to dispense with emulsifiers altogether, especially since there is a certain choice of particularly mild emulsifiers. However, the prior art lacks a satisfactorily broad range of such emulsifiers which would then also significantly broaden the application spectrum of correspondingly mild cosmetic preparations which are tolerated by the skin.
An object of the present invention was therefore to provide cosmetic and dermatological preparations having excellent skincare properties.
A disadvantage, in particular of O/W emulsions, is often their inadequate stability to relatively high electrolyte concentrations, which manifests itself in phase separation. This can indeed sometimes lead to problems, even in the case of W/O emulsions, although this is by no means as important here as in the case of O/W systems. Although these can often be remedied to a certain extent through appropriate choice of the emulsifier system, other disadvantages, however, arise just as often.
On the other hand, it is often desireable to use certain electrolytes in order to be able to utilize their other physical, chemical or physiological properties.
The concentrations of all of the constituents of a cosmetic or dermatological preparation are usually chosen in units such as % by weight, mol % and the like. In view of their greater or lesser dissociation into cations and anions, often in several dissociation stages, it sometimes appears more advantageous for the description of the present invention and its technical background, to start from the ionic strength of a given electrolyte in its solution.
The ionic strength I of an electrolyte solution is defined as
I
=
1
2
Bleckmann Andreas
Hamer Gunhild
Riedel Heidi
Schneider Günther
Beiersdorf AG
Dees Jose′ G.
Haghighatian Mina
Norris & McLaughlin & Marcus
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