Drug – bio-affecting and body treating compositions – Live hair or scalp treating compositions – Shaving preparation
Reexamination Certificate
1999-12-22
2001-09-11
Spear, James M. (Department: 1615)
Drug, bio-affecting and body treating compositions
Live hair or scalp treating compositions
Shaving preparation
C606S009000
Reexamination Certificate
active
06287549
ABSTRACT:
The invention relates to a method for preventing the regrowth of hairs and/or for eliminating hairs using a composition which is intended to be applied to the skin before a laser treatment and comprises microparticles of specific size comprising at least one chromophore.
It is known to use the laser technique in order to remove hairs. For example, U.S. Pat. Nos. 3,538,919 and 4,617,926 describe depilation methods using the light energy which is emitted by a laser and is transmitted by an optical fibre, which targets and eliminates the hairs one by one. Furthermore, U.S. Pat. No. 5,059,919 describes a depilation method using a laser placed at the orifice of the pilosebaceous unit whose light energy is absorbed by the melanin situated in the dermic papilla. These methods are time-consuming and may cause discomfort to the subject being treated, in particular due to the slowness of the method and the possible tugging on the hairs when they are put in place in order to be irradiated.
In order to solve the problem of the slowness of the methods described above, U.S. Pat. No. 5,425,728 then proposed irradiating a large area of the skin with a laser after application to this part of the skin of a composition comprising a chromophore exhibiting significant absorbence at the wavelength of the light emitted by the laser. This chromophore is more particularly carbon particles of average size between 10 and 20 nm. However, this method has certain drawbacks: the small size of these particles does not allow the pilosebaceous units to be penetrated deeply and selectively. This is because these particles may end up in the pores of the skins or alternatively in wrinkles, which causes an undesired lesion of parts of the skin during the irradiation. Furthermore, in spite of the use of ultrasound or prolonged massage, the carbon particles do not reach deeply into the pilosebaceous units. In order to increase the depth and the selectivity of the penetration of the particles in the pilosebaceous unit, the same author proposes, in Patent CA 2 131 750, a similar method using particles of carbon (graphite) of larger size (1 &mgr;m). In this method, the author describes the need to fracture the 1 &mgr;m carbon particles in order to allow them to penetrate to the bottom of the pilosebaceous units. In order to do this, it is necessary to apply 10 to 15 successive laser shots. Therefore, compared with the method described in U.S. Pat. No. 5,425,728, this method (described in Patent CA 2 131 750) improves the penetration in depth of the carbon particles into the pilosebaceous units, but has a major drawback: the fracture of a 1 &mgr;m carbon particle into two particles of smaller size is accompanied by the emission of a shockwave that propagates through the tissue. The need to apply 10 to 15 successive laser shots entails the emission of 10 to 15 shockwaves. However, a large number of shockwaves significantly increases the risks of irreversible lesions in the pilosebaceous units, as well as in the surrounding tissues (undesired effect). Furthermore, these methods only describe use of a Q switch-type laser (with emission time less than 50 &mgr;s), which implies that only the mechanical effect generated by the laser is used.
The object of the present invention is therefore to provide a depilation method which overcomes the drawbacks described above.
Its object is to provide a depilation method which makes it possible to target the pilosebaceous unit with particles:
that can be ionized in a small number of laser shots in the case of using a laser radiation of emission time less than 50 &mgr;s, which reduces the risks of irreversible lesions of the perifollicular tissues, that is to say those surrounding the follicle, while making it possible to damage and/or kill the cells responsible for the growth of the hair;
and/or
can convert the light energy of the laser radiation into heat energy, in the case of using a laser radiation of emission time longer than 50 &mgr;s, which reduces the risks of irreversible lesions of the perifollicular tissues, that is to say those surrounding the follicle, while making it possible to damage and/or kill the cells responsible for the growth of the hair.
These and other objects are achieved by the present invention, which relates to a method for preventing the regrowth of hairs and/or of eliminating hairs, characterized in that it comprises the following steps:
(1) a composition comprising, in a physiologically acceptable medium, microparticles of which at least 80% by weight have a diameter of between 3 &mgr;m and 10 &mgr;m, comprising chromophores, is applied to a surface of the skin, where the hairs are situated,
(2) the composition applied in (1) which is still on the surface of the skin is removed,
(3) optionally, a composition comprising a solvent which dissolves the chromophores used in step (1) is applied to the said surface of the skin,
(4) at least one laser radiation is applied to the said surface of the skin in one or more shots, the emitted wavelength of which is absorbed by the chromophores of the composition applied in step (1) and the light energy and the emission duration of which are sufficient to damage and/or kill the cells responsible for the growth of the hair.
The diameter of the microparticles can be measured by scattering of light (Coulter counter) or by microscopy followed by image analysis.
The microparticles of determined diameters thus penetrate into the hair follicle but little through the corneal layer. This phenomenon is described in Patent EP 0375520. The microparticles selectively and progressively reach the follicular channel where the chromophores contained in these microparticles are ready to absorb the light emitted by the laser.
The microparticles may be of any kind and obtained by any known method.
They may be formed by polymers. In this case, they may be obtained after polymerization of monomers or after dispersion of synthetic or natural preformed polymers. The synthetic polymers that can be used may advantageously be selected from: polymers based on styrene, polyamides, polymers based on &bgr;-alanine, polymers derived from acrylic or methacrylic acid, polyesters derived from lactic and/or glycolic acid. The natural polymers may be selected from proteins (gelatin, albumin, casein, etc.) and polysaccharides (alginates, chitosan, etc.).
Mention may thus be made of the microparticles described in U.S. Pat. No. 4690825, WO 88/01164, EP 0391833, FR 2530250 and FR 2619385. More particularly, mention may be made of the Orgasol 2002 UD Nat Cos (Atochem) polyamide microparticles with particle size distribution centred on 5 &mgr;m (±1.5 &mgr;m) or the hollow Micropearl polymethyl methacrylate microcapsules of the company Seppic.
The microparticles used for the present invention may be formed by fatty substances. The fatty substances that can be used may advantageously be selected from derivatives of alcohols and of fatty acids, such as tristearin, semi-synthetic triglycerides or glycerol monostearate, and fatty alcohols such as cetyl alcohol. They preferably have a melting point above or equal to 50° C.
Vesicular microparticles may also be used as liposomes and, preferably, polymerized liposomes whether reverse or forward.
The methods for obtaining these microparticles (emulsifying, atomizing, microionizing in the case of chromophore particles etc.) may be adapted in order to obtain the desired particle size distribution by appropriately controlling their manufacturing process or by carrying out screening when the size distribution is broad. It is, for example, possible to adjust the size of the microparticles by selecting the polymerization solvent, the crosslinking agent or by modifying the stirring speed or time of the reaction medium. These various modifications belong to the prior art and/or are within the scope of the person skilled in the art.
The chromophores contained in the microparticles may be on the inside and/or on the surface of the microparticles, so long as their presence does not generate microparticles with a particle siz
Bouclier Martine
Buffard Karine
Mordon Serge
Pitre Frank
Sumian Chryslain
Burns Doane Swecker & Mathis L.L.P.
Centre International de Recherche Dermatologiques Galderma (C.I.
Spear James M.
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