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Stabilized photoprotective compositionRelated Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Topical Sun Or Radiation Screening, Or Tanning PreparationsStabilized photoprotective composition description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070189993, Stabilized photoprotective composition. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to compositions for skin application to protect against the harmful effects of ultraviolet radiation, particularly the effects of solar radiation. [0002] It is now generally accepted that ultraviolet radiation can be a serious health hazard. Even a limited exposure to the sun's rays which is incidental to daily life activities is known to cause chronic skin damage, including conditions such as skin aging, keratotic lesions and malignant cellular changes. Those who spend a very large amount of time in the outdoors, such as from career or recreational pursuits, have a greatly enhanced risk of developing such conditions, as well as suffering from acute adverse effects such as sunburn (erythema). Fortunately, numerous sunscreening products are commercially available at reasonable cost, for application to the skin as a protection against exposure to solar ultraviolet radiation. [0003] Sunscreening compositions take a number of forms, including lotions and creams, sticks, sprays and others. Their activity results from inclusion of one or more ultraviolet-absorbing or -scattering active ingredients, selected from lists of such ingredients that have been approved by governmental regulatory agencies in the various countries where the products are to be marketed. In the United States, sunscreening products are classified as nonprescription drugs and their approved active ingredients are listed in Title 21, Code of Federal Regulations, Part 352. [0004] The ultraviolet components of solar radiation which are known to cause skin damage include radiation having wavelengths in the range of 290-320 nanometers and generally referred to as "UV-B," as well as radiation having wavelengths in the range of 320400 nanometers and generally referred to as "UV-A..infin. "UV-C" radiation, having wavelengths in the range of 200-290 nanometers, is filtered out of solar radiation by the atmospheric ozone layer, so is not considered to be a serious threat in most of the world. Only UV-B radiation was initially considered to be of great importance, so historically the majority of approved sunscreen active ingredients are active in this range of wavelengths. However, the more recently developed products are formulated to absorb and/or scatter wavelengths in both UV-B and UV-A regions of the ultraviolet radiation spectrum. A very popular ingredient which absorbs in the UV-A range is known as "avobenzone" and has the INCI name Butyl methoxydibenzoylmethane; this substance is sold by Roche Vitamins Inc. of Parsippany, N.J. U.S.A. under the trademark PARSOL 1789. Since a particular organic molecule will exhibit its strongest absorption at a point within a range of wavelengths, and may not be very effective at some other points within that range, it is a very common practice to utilize a combination of ingredients in a product so that effective absorption over the majority of harmful wavelengths will be obtained. [0005] Although the typical sunscreening product uses one or more organic chemical active ingredients to absorb ultraviolet radiation, inorganic particulate physical sunblocking ingredients such as titanium dioxide and zinc oxide are becoming of increasing importance. These agents can provide a broad spectrum of protection, since the particles absorb, reflect and/or scatter radiation in a rather indiscriminate manner. By reducing the particle sizes to very small values, such as below about 400 nanometers, large amounts of particulate ingredients can be incorporated into a product without affecting the natural skin coloration when the product is applied. In addition, it has been discovered that product characteristics can be improved by providing the particles with coatings to modify the affinity for either water or water-insoluble formulation components. Products containing combinations of organic and particulate inorganic active ingredients, to provide protection against the full wavelength range of harmful ultraviolet radiation, have become common. [0006] Avobenzone is known to lack chemical stability in sunscreen products, and also exhibits a lack of photostability during prolonged exposure to ultraviolet radiation However, since it is a very desirable component of many sunscreening products, considerable effort has been devoted to studies of these instabilities. Combinations of some other sunscreening active agents with avobenzone have been reported to decrease the photostability of avobenzone, while combinations with certain other ingredients are reported to enhance avobenzone photostability. U.S. Pat. Nos. 5,576,354 and 5,587,150 to Deflandre et al. describe the photostabilization of avobenzone in sunscreen compositions by adding a diphenylacrylate sunscreen ingredient, such as octocrylene, in molar ratios of diphenylacrylate to avobenzone at least 0.8. U.S. Pat. 5,827,508 to Tanner et al. reports that avobenzone can be made to have improved chemical stability and photostability in a sunscreen product formulation by incorporation of surface-treated zinc oxide particles, silicone-treated zinc oxide being particularly useful for this purpose. U.S. Pat. No. 5,985,251 to Gonzenbach et al. teaches that stable sunscreen compositions can be prepared to contain avobenzone, a diphenylacrylate or benzylidene camphor derivative and a water-soluble p-methoxycinnamate. U.S. Pat. No. 5,989,528 to Tanner et al. reports that avobenzone can be made more stable by including in its formulations a diphenylacrylate derivative, when the molar ratio of diphenylacrylate to avobenzone is less than 0.8. U.S. Pat. No. 6,071,501 to Robinson states that combinations of dibenzoylmethane derivatives and octyl p-methoxycinnamate are not photostable, unless the molar ratio of the methoxycinnamate to the dibenzoylmethane is in the range of 0.15:1 to 1:1. U.S. Pat. No. 6,090,369 to Stewart proposes a stable sunscreen composition that contains avobenzone, octyl methoxycinnamate and either titanium dioxide or zinc oxide; octocrylene is an optional component. [0007] Prolonged protection against the UV-A radiation is very important, as evidenced by the numerous approaches that have been taken to improve avobenzone photostability. It is always desired to improve the performance characteristics of sunscreening products, and the present invention provides a further improvement over the current state of the art. SUMMARY OF THE INVENTION [0008] The invention includes a stable photoprotective composition containing the active ingredients avobenzone, zinc oxide and phenylbenzimidazole sulfonic acid. The phenylbenzimidazole sulfonic acid component provides ultraviolet-absorbing properties and acts to stabilize avobenzone against photodegradation. In general, the avobenzone will be present in amounts about 1 to about 3 weight percent, the zinc oxide will be present in amounts about 1 to about 25 weight percent and the phenylbenzimidazole sulfonic acid will be present in amounts about 0.5 to about 4 weight percent. When the photoprotective composition is in the form of an emulsion, other components will include water and an emulsifier. DETAILED DESCRIPTION [0009] In this document, chemical substances are wherever possible identified by either their chemical names or by adopted names taken from J. A. Wenninger et al., Eds., International Cosmeetic Ingredient Dictionary and Handbook, 8.sup.th Ed., The Cosmetic, Toiletry, and Fragrance Association, Washington, D.C., 1999. Percentages are intended to mean "weight percent," unless the context clearly indicates otherwise. [0010] Sunscreening compositions generally are permitted to contain only the active ingredients that have been approved by governmental authorities, and frequently those authorities also specify the amounts of each approved ingredient is that are permitted to be present in a product. The following active ingredients are currently listed in Title 21, Code of Federal Regulations, Section 352.10 as being approved for inclusion in products sold in the United States as non-prescription sunscreen drugs: aminobenzoic acid; avobenzone; cinoxate; dioxybenzone; homosalate; menthyl anthranilate; octocrylene; octyl methoxycinnamate; octyl salicylate; oxybenzone; Padimate O; phenylbenzimidazole sulfonic acid; sulisobenzone; titanium dioxide; trolamine salicylate; and zinc oxide. Section 352.20 of the same Title 21 describes the permitted combinations of ingredients; in general, each active ingredient in a permitted combination is required to be present in at least a sufficient amount to contribute an SPF value of 2, so an amount making this contribution is considered herein to be the minimum "sunscreening-effective" concentration of an active ingredient. The regulations prescribe maximum concentrations of 3 percent avobenzone, 25 percent zinc oxide and 4 percent phenylbenzimidazole sulfonic acid in a sunscreening product. Some countries allow the use of other active ingredients and these are also suitable for inclusion as components of the compositions of this invention, where their use is legally permitted; in addition, the permitted concentrations of active ingredients vary somewhat by country. [0011] Beginning in September 2002, the official adopted name in the United States for menthyl anthranilate will become "meradimate," the official name for octyl methoxycinnamate will become "octinoxate," the official name for octyl salicylate will become "octisalate" and the official name for phenylbenzimidazole sulfonic acid will become "ensulizole." [0012] Title 21, in Section 352.3, defines the term "Sun Protection Factor," typically abbreviated as "SPF," which is determined by testing unprotected and sunscreen-protected skin using standardized intensities and amounts of ultraviolet radiation. Protected skin for this testing has been treated by an application of a sunscreen product at the rate of 2 mg/cm.sup.2, and it is intended that the compositions of this invention will be applied by a user at that same rate to to achieve the rated protection levels. [0013] The present invention relates to zinc oxide and avobenzone-containing sunscreen compositions which are stabilized against avobenzone photodegradation by the inclusion of phenylbenzimidazole sulfonic acid. The avobenzone generally will be present in concentrations about 1 to about 3 percent by weight. The zinc oxide generally will be present in concentrations about 1 to about 25 percent by weight, more preferably about 5 to about 15 percent by weight. Useful concentrations of the phenylbenzimidazole sulfonic acid for providing photostability range from about 0.5 to about 4 weight percent, more preferably about 1 to about 3 weight percent. The specific amount of phenylbenzimidazole sulfonic acid that is required to be present in a particular composition to achieve acceptable photostability will depend upon the concentration of avobenzone and, possibly, also on the concentration of zinc oxide; those skilled in the art will be able to easily conduct testing for determining appropriate amounts for their purposes, such as by the method described in the example, infra. [0014] As will be shown, the photostability enhancement of avobenzone by phenylbenzimidazole sulfonic acid is greater at higher zinc oxide concentrations, so zinc oxide concentrations at least about 6 weight percent and up to about 25 weight percent are preferred for compositions of the invention. [0015] Useful sunscreen compositions according to the present invention can be prepared in the form of fluid suspensions, gels, sticks and others, utilizing formulation parameters known in the art. However, the compositions of the invention are more typically emulsions, such as lotions and creams. In many instances it will be preferred to prepare emulsions of the oil-in-water type, since these can appear to the skin as being aqueous in character and therefore give a more pleasant sensation while they are being applied. However, the water-in-oil type of emulsion is also useful since, after application, contained water evaporates; both types of emulsions will leave a nonaqueous residue on the skin. [0016] Emulsion compositions of the invention are required to contain, in addition to the active sunscreening agents, water and at least one emulsifier. One or more other types of components will frequently also be present, such as, without limitation, emulsion builders, emollients, humectants, dry-feel modifiers, waterproofing agents, antimicrobial preservatives, antioxidants, chelating agents, fragrances, colorants and insect repellents. Emulsions/Emulsifiers [0017] A stable emulsion is a mixture of two immiscible liquids, i.e. liquids that are not mutually soluble, but in the presence of an emulsifier, are mechanically agitated and shaken so thoroughly together that one liquid forms drops in the other one, giving the mixture the appearance of a homogeneous liquid. Liquids can include materials which are solid or solid-like at room temperature, but will liquify at a higher temperature during processing. The presence of an emulsifier enables one of the immiscible liquids to remain in a continuous form, while allowing the other immiscible liquid to remain in a dispersed droplet form. Thus, one function of an emulsifier, a stabilizing compound, is to assist in the production of a stable emulsion. A secondary function of emulsifiers is to provide a thickening or "bodying" to an emulsion. Typically, emulsifiers are molecules with non-polar and polar parts that are able to reside at the interface of the two immiscible liquids. As used herein in reference to the water-in-oil emulsifiers, the term "HLB value" means the hydrophilic/lipophilic balance. The HLB value has been used by those skilled in the emulsion art for selecting emulsifiers useful to prepare, inter alia, water-in-oil emulsions. See U.S. Pat. No. 4,177,259 and references cited therein. [0018] An oil-in-water (o/w) emulsion is a mixture where "oil," or water-insoluble liquid, droplets (the discontinuous phase) are dispersed in a continuous aqueous phase. A water-in-oil (w/o) emulsion is a mixture where aqueous phase droplets (the discontinuous phase) are dispersed in "oil" (a continuous water-insoluble phase). Preferably the composition of the present invention is an oil-in-water emulsion where the oil-soluble actives are combined to form the oil phase, prior to mixture with the water phase. The type of emulsion formed, oil-in-water (o/w) or water-in-oil (w/o), is sometimes determined by the volume ratio of the two liquids provided the ratio is sufficiently high. For example, with 5% water and 95% oil (an o/w phase ratio of 19), the emulsion likely will become w/o. For moderate phase ratios (generally <3), the type of emulsion is decided by several factors, such as order of addition or type of emulsifier. One liquid slowly added to a second liquid with agitation usually results in the second liquid being the continuous phase. Another factor is preferred solubility of the emulsifier, as the phase in which the emulsifier is more soluble will likely be continuous. [0019] More complex emulsions such as double emulsions are formed where an emulsion is dispersed in a continuous phase. For example, in an oil in-water-in oil (o/w/o) emulsion, the water in a continuous water phase containing dispersed oil droplets, is itself dispersed in a continuous oil phase. Similarly, in a water-in oil-in water (w/o/w) emulsion, the oil in a continuous phase containing dispersed water droplets, is itself dispersed in a continuous water phase. These more complex emulsions find use as a system for slow delivery, extraction, etc. [0020] Typical suitable emulsifiers having an HLB value about 1 to about 7 include sorbitan monooleate, sorbitan sesquioleate, sorbitan isostearate, sorbitan trioleate, PEG-22/dodecyl glycol copolymer, PEG45/dodecyl glycol copolymer, polyglyceryl-3-diisostearate, polyglycerol esters of oleic/isostearic acid, polyglyceryl-6 hexaricinolate, polyglyceryl-4 oleate, polyglyceryl-4 oleate/PEG-8 propylene glycol cocoate, oleamide DEA, sodium glyceryl oleate phosphate and hydrogenated vegetable glycerides phosphate. [0021] Other emulsifiers useful in the present invention may be non-ionic, liquid or solid at room temperature and preferably compatible, i.e., soluble and stable with emollients. Preferred emulsifiers have a HLB value of less than about 5, e.g., sorbitan sequioleate (HLB value is 3.7), sorbitan monooleate (HLB value is 4.3) and sorbitan trioleate (HLB value is 1.8). Other preferred emulsifiers include polymeric emulsifiers such as copolymers of C.sub.10-C.sub.30 alkyl acrylates and one or more monomers of acrylic acid or methacrylic acid, also known as Pemulen.RTM. TRI and TR2, trademark of B. F. Goodrich Inc., Cincinnati, Ohio U.S.A. Other emulsifiers include sorbitan esters such as sorbitan isostearate available as Crill 6, trademark of Croda Inc. of New York, N.Y. U.S.A.; polyglyceryl-3 distearate available as Cremophor, trademark of BASF, Parsippany N.J. U.S.A.; and carbomer, which is a homopolymer of acrylic acid crosslinked with an allyl ether of sucrose, available as Carbopol 941, trademark of B.F. Goodrich, s Cleveland, Ohio U.S.A.; surfactants such as such as DEA-cetyl phosphate, also known as Amphisol.RTM., trademark of Bernel Chemical Co., Englewood, N.J. U.S.A.; mixtures of arachidyl alcohol, behenyl alcohol and arachidyl glucoside, such as is sold by Seppic Inc. of Fairfield, N.J. U.S.A. using the trademark Montanov 202; and mixtures of cetearyl glucoside and cetearyl alcohol, such as is sold by Cognis Corporation of Cincinnatti, Ohio U.S.A. using the trademark Emulgade PL 68150. Continue reading about Stabilized photoprotective composition... Full patent description for Stabilized photoprotective composition Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Stabilized photoprotective composition patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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