U.S. patent application number 11/680306 was filed with the patent office on 2007-08-16 for stabilized photoprotective composition.
This patent application is currently assigned to Schering-Plough Healthcare Products, Inc.. Invention is credited to Donathan G. Beasley, Thomas A. Meyer.
Application Number | 20070189993 11/680306 |
Document ID | / |
Family ID | 32110076 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070189993 |
Kind Code |
A1 |
Meyer; Thomas A. ; et
al. |
August 16, 2007 |
STABILIZED PHOTOPROTECTIVE COMPOSITION
Abstract
Sunscreen compositions contain the active ingredients
avobenzone, zinc oxide and phenylbenzimidazole sutfonic acid. The
phenylbenzimidazole sulfonic acid protects avobenzone against
photodegradation.
Inventors: |
Meyer; Thomas A.;
(Germantown, TN) ; Beasley; Donathan G.; (Memphis,
TN) |
Correspondence
Address: |
SCHERING-PLOUGH CORPORATION;PATENT DEPARTMENT (K-6-1, 1990)
2000 GALLOPING HILL ROAD
KENILWORTH
NJ
07033-0530
US
|
Assignee: |
Schering-Plough Healthcare
Products, Inc.
|
Family ID: |
32110076 |
Appl. No.: |
11/680306 |
Filed: |
February 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10645253 |
Aug 21, 2003 |
|
|
|
11680306 |
Feb 28, 2007 |
|
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|
60405404 |
Aug 22, 2002 |
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Current U.S.
Class: |
424/59 |
Current CPC
Class: |
A61K 8/4946 20130101;
A61K 8/35 20130101; A61Q 17/04 20130101; A61K 8/27 20130101 |
Class at
Publication: |
424/059 |
International
Class: |
A61Q 17/04 20060101
A61Q017/04; A61K 8/18 20060101 A61K008/18 |
Claims
1-16. (canceled)
17. A sunscreen composition comprising avobenzone and sufficient
phenylbenzimidazole sulfonic acid to stabilize the avobenzone
against photodegradation, wherein the composition does not contain
a diester or polyester of a naphthalene dicarboxylic acid.
18. The composition of claim 17, wherein the concentration of
avobenzone is about 1 to about 3 weight percent, and the
concentration of phenylbenzimidazole sulfonic acid is about 0.5 to
about 4 weight percent.
19. The composition of claim 17, further containing zinc oxide
20. The composition of claim 17, wherein in the zinc oxide is
present in an amount of about 3 weight percent.
21. The composition of claim 17, wherein the concentration of
phenylbenzimidazole sulfonic acid is about 1 weight percent.
22. The composition of claim 17, which is in the form of an
emulsion.
23. The composition of claim 22, wherein the emulsion is an
oil-in-water emulsion.
24. A method for protecting the skin against ultraviolet radiation,
comprising applying to the skin an effective amount of the
composition of claim 17.
25. A method for protecting the skin against ultraviolet radiation,
comprising applying to the skin an effective amount of the
composition of claim 19.
26. A method for increasing the SPF value of a sunscreen
composition comprising avobenzone, the method comprising adding to
the composition an amount of phenylbenzimidazole sulfonic acid
sufficient to photostabilize avobenzone, thereby increasing the SPF
value, wherein the composition does not contain a diester or
polyester of a naphthalene dicarboxylic acid.
27. The method of claim 26, wherein the composition further
comprises zinc oxide.
28. The method of claim 27, wherein zinc oxide is present in the
composition in an amount of about 3 weight percent.
29. The method of claim 26, wherein the concentration of avobenzone
is about 1 to about 3 weight percent, and the concentration of
phenylbenzimidazole sulfonic acid is about 0.5 to about 4 weight
percent.
30. The method of claim 26 wherein the amount of
phenylbenzimidazole sutfonic acid is about 1 weight percent.
31. A method for improving the photostability of avobenzone in a
sunscreen composition, the method comprising adding to the
composition an amount of phenylbenzimidazole sulfonic acid
sufficient to photostabilize avobenzone, wherein the composition
does not contain a diester or polyester of a naphthalene
dicarboxylic acid.
32. The method of claim 3 1, wherein the composition further
comprises zinc oxide.
33. The method of claim 32, wherein zinc oxide is present in the
composition in an amount of about 3 weight percent.
34. The method of claim 31, wherein the concentration of avobenzone
is about 1 to about 3 weight percent, and the concentration of
phenylbenzimidazole sulfonic acid is about 0.5 to about 4 weight
percent.
35. The method of claim 31, wherein the amount of
phenylbenzimidazole sulfonic acid is about 1 weight percent.
Description
[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.
[0022] The foregoing emulsifying agents are mentioned only by way
of example. Many other compounds and mixtures are useful, as will
be readily appreciated by those skilled in the art.
[0023] During preparation of the emulsion, an acid or a base may be
added to adjust the pH of one or more ingredients, e.g. to adjust
the viscosity of a polymeric thickener, prior to its inclusion in
the sunscreen composition. For example, triethanolamine, a base,
can be used to increase the pH of the water phase and consequently,
modify the desired viscosity of the emulsion. The sunscreen can
have a pH of about 6.5 to about 8, preferably from about 6.5 to
about 7.5, more preferably the pH of the sunscreen is neutral, i.e.
about 7.0. When present together in a composition, certain
ingredients such as triethanolamine and stearic acid can form an
emulsifier. As is well known, inorganic salts such as sodium
chloride also are frequently included in emulsion compositions to
obtain desired product stability and other physical properties.
[0024] Conveniently, one or more emulsifiers can be used in the
compositions of the present invention in amounts ranging from about
0.05 to about 20 weight percent of the emulsion, preferably from
about 0.1 to about 15%, more preferably from about 5 to about
10%.
Water
[0025] Water is employed in amounts effective to form the emulsion.
For hydrophilic or water-loving ingredients, the amount of water
should be sufficient to at least solubilize these ingredients. For
hydrophobic or water-repelling ingredients, the water should be
employed in amounts to serve as the continuous phase of an oil-in
water emulsion. Thus, amount of water in the emulsion or
composition can range from about 2 to 95 weight %, preferably from
50 to 85%. It frequently is desirable to use purified water, to
enhance the predictability of product characteristics.
Emollients
[0026] An emollient is an oleaginous or oily substance which helps
to smooth and soften the skin, and may also reduce its roughness,
cracking or irritation. Typical suitable emollients include
mineral, oil, having a viscosity in the range of 50 to 500
centipoise (cps), lanolin oil, coconut oil, cocoa butter, olive
oil, almond oil, macadamia nut oil, aloe extracts such as aloe vera
lipoquinone, synthetic jojoba oils, natural sonora jojoba oils,
safflower oil, corn oil, liquid lanolin, cottonseed oil and peanut
oil.
[0027] Other suitable emollients include squalane, castor oil,
polybutene, odorless mineral spirits, sweet almond oil, avocado
oil, calophyllum oil, ricin oil, vitamin E acetate, olive oil,
silicone oils such as dimethylopolysiloxane and cyclomethicone,
linolenic alcohol, oleyl alcohol, the oil of cereal germs such as
the oil of wheat germ, isopropyl palmitate, octyl palmitate which
is commercially available as Lexol EHP, tradename of Inolex Co. of
Philadelphia, Pa. U.S.A., isopropyl myristate, hexadecyl stearate,
butyl stearate, decyl oleate, acetyl glycerides, the octanoates and
benzoates of (C.sub.12-C.sub.15) alcohols, the octanoates and
decanoates of alcohols and polyalcohols such as those of glycol and
glycerol, ricinoleates of alcohols and polyalcohols such as those
of isopropyl adipate, hexyl laurate and octyl dodecanoate.
[0028] Other suitable emollients which are solids or semi-solids at
ambient temperatures may be used in amounts sufficient to provide
liquid topical compositions. Such solid or semi-solid cosmetic
emollients include hydrogenated lanolin, hydroxylated lanolin,
acetylated lanolin, petrolatum, isopropyl lanolate, butyl
myristate, cetyl myristate, myristyl myristate, myristyl lactate,
cetyl alcohol, isostearyl alcohol and isocetyl lanolate. One or
more emollients can optionally be included in the sunscreen
emulsion in an amount ranging from about 10 to about 50 weight %,
preferably about 20 to about 40%.
Humectants
[0029] A humectant is a moistening agent that promotes retention of
water due to its hygroscopic properties. Suitable humectants
include urea, glycerin, polymeric glycols such as poyethylene
glycol and polypropylene glycol, and sorbitols. One or more
humectants can optionally be included in the in the sunscreen in
amounts from about 1 to 10 weight %.
Dry-Feel Modifiers
[0030] A dry-eel modifier is an agent which, when incorporated in
an emulsion, imparts a "dry feel" to the skin when the emulsion
dries. Dry-feel modifiers may also reduce sunscreen migration on
the skin. Dry feel modifiers can include starches, talc, kaolin,
chalk, zinc oxide, silicone fluids, inorganic salts such as barium
sulfate and sodium chloride, C.sub.6 to C.sub.12 alcohols such as
octanol; sulfonated oils; surface treated silica, precipitated
silica, fumed silica such as is Aerosil.RTM. available from the
Degussa Inc. of New York, N.Y. U.S.A. or mixtures thereof
dimethicone, a mixture of mixture of methylated linear siloxane
polymers, available as DC200 fluid, tradename of Dow Corning,
Midland, Mich. U.S.A. One or more dry-feel modifiers can optionally
be included in the sunscreen in amounts ranging from 0.01 to about
20 weight %, more preferably 20 from about 0.5 to about 6 weight
%.
Waterproofing Agents
[0031] A waterproofing agent is a hydrophobic material that imparts
film forming and waterproofing characteristics to an emulsion.
Typical suitable waterproofing agents include copolymers derived
from polymerization of octadecene-1 and maleic anhydride in
accordance with the published procedures such as those in U.S. Pat.
No. 3,860,700 and Reissue No. 28,475. A preferred waterproofing
agent is a polyanhydride resin, also known as PA-18, tradename of
the Chevron Chemicals Co., San Francisco, Calif. U.S.A. Another
preferred waterproofing agent is a copolymer of vinyl pyrollidone
and eicosene monomers such as Ganex Polymer, tradename of ISP Inc.
of Wayne, N.J. U.S.A.
[0032] By the term "waterproofing effective amount of at least one
waterproofing agent" means the waterproofing agent(s) is used in
amounts effective to allow the sunscreen to remain on the skin
after exposure to circulating water for at least 80 minutes using
the procedures described in "Sunscreen Drug Products for OTC Human
Use", Federal Register, Vol. 43, Aug. 25, 1978, Part 2, pp
38206-38269. One or more waterproofing agents can optionally be
included in the sunscreen composition in an amount ranging from
about 0.01 to about 10.0 weight percent, preferably about 10 to
about 10.0 percent.
Antimicrobial Preservatives
[0033] An antimicrobial preservative is a substance or preparation
which destroys, prevents or inhibits the multiplication/growth of
microorganisms in the sunscreen composition and may offer
protection from oxidation. Preservatives are used to make
self-sterilizing, aqueous based products such as emulsions. This is
done to prevent the development of microorganisms that may be in
the product during manufacturing and distribution, and during use
by consumers who may inadvertently contaminate the products.
Typical preservatives include the lower alkyl esters of
para-hydroxybenzoates (parabens) especially, methylparaben,
propylparaben, isobutylparaben and mixtures thereof, benzyl alcohol
and benzoic acid. One or more antimicrobial preservatives can
optionally be included in the sunscreen composition in an amount
ranging from about 0.001 to about 10 weight percent, more
preferably about 0.05 to about 2 percent.
Antioxidants
[0034] An antioxidant is a natural or synthetic substance added to
the sunscreen to protect from or delay its deterioration due to the
action of oxygen from the air, or to protect the skin against
damage from free radicals that form due to the action of
ultraviolet radiation. Typical suitable antioxidants include
propyl, octyl and dodecyl esters of garlic acid, butylated
hydroxyanisole (BHA) which is usually as a mixture of ortho and
meta isomers, butylated hydroxytoluene (BHT), nordihydroguaiaretic
acid, vitamin E, vitamin E acetate, vitamin C and alkylated
parabens such as methylparaben and propylparaben. One or more
antioxidants can optionally be included in the sunscreen
composition in an amount ranging from about 0.001 to about 5 weight
percent, preferably about 0.05 to about 2 percent.
Chelating Agents
[0035] Chelating agents are substances used to complex or bind
metallic ions in a frequently heterocylic ring structure so that
the ion is held by chemical bonds from members of the ring.
Suitable chelating agents include ethylene diaminetetraacetic acid
(EDTA), EDTA disodium, calcium disodium edetate, EDTA trisodium,
EDTA tetrasodium and EDTA dipotassium. One or more chelating agents
can optionally be included in the sunscreen in amounts ranging from
about 0.001 to about 0.1 weight percent.
Fragrances
[0036] Fragrances are aromatic compounds which can impart an
aesthetically pleasing aroma to the sunscreen composition. Typical
fragrances include aromatic materials extracted from botanical
sources (i.e. rose petals, gardenia blossoms, jasmine flowers,
etc.) which can be used alone or in any combination to create
essential oils. Alternatively, alcoholic extracts may be prepared
for compounding fragrances. One or more fragrances can optionally
be included in the sunscreen composition in an amount ranging from
about 0.001 to about 10 weight percent, preferably about 0.05 to
about 5 percent.
Insect Repellents
[0037] It frequently is desirable to provide protection against
biting and stinging insects, since sunscreens are used in outdoor
environments. Useful insect repelling ingredients include synthetic
agents such as N,N-diethyl-m-toluamide, also commonly known as
"DEET," and natural plant extracts such as citronella, geraniol and
others.
Dispensers
[0038] The sunscreen emulsions of the present invention can be
stored or dispensed in any container suitable for convenient
delivery, for example pouring or spraying. Such containers can
include, but are not limited to, jars and bottles which permit
pouring of the contents, bottles having lotion pumps, pump spray
bottles and pressurized aerosol canisters.
[0039] Certain aspects of the invention will be further described
in the following example, which is not intended to limit the scope
of the invention as defined by the appended claims.
EXAMPLE
[0040] Comparative photoprotective lotion "A" is prepared using the
following ingredients: TABLE-US-00001 Component Wt. Percent Sodium
cetearyl sulfate 0.5 *PEG-30 dipolyhydroxystearate 0.3 *Cetearyl
glucoside 1 *Cetearyl alcohol 1 *Octyl palmitate 5 *Avobenzone 2
*Octyl salicylate 5 *Octocrylene 1.5 *Homosalate 12 *Isopropyl
laurate 5 *Propyl paraben 0.1 Benzyl alcohol 1 Xanthan gum 0.35
Magnesium aluminum silicate 1 Disodium EDTA 0.01 Methyl paraben 0.2
Polyethylene glycol 400 4 Water q.s. to total 100%
[0041] Modifications of this lotion are prepared to additionally
include 3, 6 and 10 wt percent of a hydrophobic silicone-coated
zinc oxide, which is the commercial product sold using the
trademark Z-COTE HP1 by BASF Corporation of Mount Olive, N.J.
U.S.A. These modified lotions are identified below, respectively,
as "A1," "A2" and "A3."
[0042] According to an aspect of the present invention,
photoprotective lotion "B" is prepared using the following
ingredients: TABLE-US-00002 Component Wt. Percent Sodium cetearyl
sulfate 0.5 *PEG-30 dipolyhydroxystearate 0.3 *Cetearyl glucoside 1
*Cetearyl alcohol 1 *Octyl palmitate 8.5 *Avobenzone 2 *Octyl
salicylate 5 *Octocrylene 1.5 *Homosalate 5 *Isopropyl laurate 8.5
*Propyl paraben 0.1 Benzyl alcohol 1 Xanthan gum 0.35 Magnesium
aluminum silicate 1 Disodium EDTA 0.01 Methyl paraben 0.2
Polyethylene glycol 400 4 Triethanolamine 0.8 Phenylbenzimidazole
sulfonic acid 1 Water q.s. to total 100%
[0043] Modifications of this base lotion are prepared to
additionally include 3, 6 and 10 wt. percent of the
above-identified Z-COTE HPI zinc oxide. These modified lotions are
identified below, respectively, as "B1," "B2" and "B3."
[0044] All lotions are prepared using the following procedure:
[0045] (1) the ingredients identified above with an asterisk are
combined with mixing and heated to about 65.degree. C. then, after
a homogenous mixture is obtained, the zinc oxide (if required) is
added; [0046] (2) the water, disodium EDTA, polyethylene glycol,
triethanolamine (if required) and phenylbenzimidazole sulfonic acid
(if required) are combined and mixed to obtain homogeneity,
magnesium aluminum silicate and xanthan gum are added and the
combination is mixed and heated to about 65.degree. C., then the
methylparaben and sodium cetearyl sulfate are added; [0047] (3) the
heated combination of (1) is added to the heated combination of
(2), with continuous mixing to form an emulsion, and the emulsion
is homogenized by passing through a commercial homogenizer for 5
minutes; [0048] (4) under continuous mixing, the emulsion is
allowed to cool to less than about 40.degree. C., then the benzyl
alcohol is added and the mixture continues to cool to room
temperature; and [0049] (5) additional water is added, with mixing,
as needed to compensate for evaporative losses occurring during the
procedure.
[0050] The various lotions have the following properties:
TABLE-US-00003 Lotion SPF Value Lotion pH A 23.3 5.41 A1 24.3 A2
36.7 A3 42.9 7.11 B 26.5 B1 27.5 B2 38.9 B3 44 7.57
[0051] The lotions are tested to determine photostability by
weighing up to 20 milligram portions (the target being 15
milligrams) of each lotion onto glass microscope slides having a
surface area of 12.5 cm.sup.2 and spreading the lotion evenly over
the upper surface of the slides. Samples are allowed to air-dry in
the dark for at least 30 minutes and then are placed on a rotating
turntable and irradiated using a WG 320 filtered 1000-watt xenon
arc solar simulator (Kratos Analytical, Model LH-1 53, currently
being sold by Spectral Energy Corp., Westwood, N.J. U.S.A.)
delivering 30 joules of energy over a period of about 60
minutes.
[0052] The avobenzone content of irradiated lotion samples,
selected to have had 13-17 milligrams of lotion applied to a slide,
and non-irradiated control lotions (having similar amounts spread
onto slides and dried as described above) is analyzed by
ultraviolet absorption spectrophotometry at a wavelength of 360
nanometers. Each slide is placed into 50 milliliters of isopropanol
in a glass jar, the dried sunscreen coating is disrupted from the
slide by rubbing with a rubber finger cot-covered finger, the jar
is closed and vigorously shaken to solubilize the sunscreen active
ingredients and then samples of the alcohol solution are analyzed
in the spectrophotometer. Absorbance values for samples are
compared to curves obtained from isopropanol solutions of standard
sunscreen preparations that contain known amounts of avobenzone The
following results are obtained: TABLE-US-00004 % of original
Avobenzone % of original Avobenzone Lotion before exposure after
exposure A 100.8 .+-. 1.0 81.5 .+-. 6.6 A1 99.0 .+-. 0.5 76.8 .+-.
0.9 A2 96.6 .+-. 7.5 72.9 .+-. 1.1 A3 101.6 .+-. 3.3 66.8 .+-. 4.3
B 98.6 .+-. 1.6 89.1 .+-. 2.7 B1 97.8 .+-. 1.6 89.2 .+-. 3.8 B2
100.9 .+-. 0.6 91.1 .+-. 1.7 B3 101.0 .+-. 3.2 87.2 .+-. 5.2
[0053] These results show that avobenzone photostability is
enhanced when phenylbenzimidazole sulfonic acid is present in
sunscreen compositions. Zinc oxide does not adequately protect
avobenzone against photodegradation, and photostability is improved
by also including phenylbenzimidazole sulfonic acid in the
composition.
* * * * *