Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
2000-06-12
2001-04-03
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S060000, C424S400000, C424S401000
Reexamination Certificate
active
06210658
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a stable sunscreen composition for topical application to human skin to protect the skin against UV radiation damage. More particularly, the present invention is directed to the use of a barium compound, particularly barium sulfate, that is surprisingly effective in stabilizing the combination of a UV-A dibenzoylmethane derivative, particularly butyl methoxydibenzoylmethane, and a methoxycinnamate derivative UV-B sunscreen compound, particularly ethylhexyl-p-methoxycinnamate or octyl methoxycinnamate, such that the sunscreen combination is a more effective sunscreen, having a surprisingly increased sunscreen protection factor (SPF) and such that both the dibenzoylmethane derivative and methoxycinnamate derivative are more effective over a longer period of time so that the sunscreen composition need not be applied to the skin as frequently.
BACKGROUND OF THE INVENTION AND PRIOR ART
It is well known that ultraviolet light having a wavelength between about 280 nm or 290 nm and 320 nm (UV-B) is harmful to human skin, causing burns that are detrimental to the development of a good sun tan. UV-A radiation, while producing tanning of the skin, also can cause damage, particularly to very lightly colored, sensitive skin, leading to reduction of skin elasticity and wrinkles. Therefore, a sunscreen composition should include both UV-A and UV-B filters to prevent most of the sunlight within the full range of about 280 nm to about 400 nm from damaging human skin.
The UV-B filters that are most widely used commercially in sunscreen compositions are paramethoxycinnamic acid esters, such as 2-ethylhexyl paramethoxycinnamate, commonly referred to as octyl methoxycinnamate (e.g., PARSOL MCX), octyl salicylate; homomenthyl salicylate, and others.
The UV-A filters most commonly used in commercial sunscreen compositions are the dibenzoylmethane derivatives, particularly butyl methoxybenzoylmethane (avobenzone), 4-isopropyl dibenzoylmethane (EUSOLEX 8020), and other dibenzoylmethane derivatives described in U.S. Pat. Nos. 4,489,057; 4,387,089 and 4,562,067, hereby incorporated by reference. It is also well known that some of the UV-A filters, or combinations of UV-A and UV-B filters, suffer in photochemical stability (see R. M. Sayre, J. C. Dowdy,
Photostability Testing of Avobenzone, Cosmetics
&
Toiletries Magazine
114, 85-91 (May, 1999); and N. Tarras-Wahlberg et al.,
Changes in Ultraviolet Absorption of Sunscreens After Ultraviolet Irradiation
, J. Invest. Derm. 113, 547-553 (1999)). Accordingly, when a UV-B filter, such as 2-ethylhexyl-p-methoxycinnamate (PARSOL MCX), is combined with a dibenzoylmethane derivative UV-A compound, such as PARSOL 1789, the combination becomes less photochemically stable necessitating repeated, frequent coatings over the skin for sufficient UV radiation protection (see Bonda, et al.
The Photochemistry of Sunscreen Photostability
, page 5).
In accordance with the principles of the present invention, it has been found, quite surprisingly, that by including a barium compound, such as barium sulfate, into a sunscreen formulation containing a combination of a UV-A dibenzoylmethane derivative, particularly avobenzone, and a methoxycinnamate derivative UV-B sunscreen agent, such as octyl methoxycinnamate, the sunscreen combination is photochemically stabilized so that the sunscreen composition is more effective for filtering out UV-A and UV-B radiation; the composition filters both UV-A and UV-B radiation for longer periods of time; and, therefore, the sunscreen formulation need not be applied to the skin as frequently while maintaining effective skin protection against UV-A and UV-B radiation.
By the addition of the barium compound, the cosmetic sunscreen formulation can maintain surprisingly effective skin protection against UV radiation both in the UV-A and UV-B range, with or without additional common sunscreen additives, such as benzophenone 3, octocrylene, and/or titanium dioxide. Preferably, the ratio of UV-A to UV-B filter compounds is in the range of about 0.1:1 to about 3:1, preferably about 0.1:1 to about 0.3:1, most preferably about 0.24:1.
SUMMARY OF THE INVENTION
In brief, the present invention is directed to sunscreen compositions containing a dibenzoylmethane derivative UV-A filter compound, such as butyl methoxydibenzoylmethane (avobenzone), together with a UV-B methoxycinnamate derivative, such as octyl methoxycinnamate, and a barium compound stabilizer for the combination of sunscreen agents.
Surprisingly, it has been found the barium compound, particularly barium sulfate, is quite effective in stabilizing the combination of avobenzone and ethylhexyl-p-methoxycinnamate compounds making them more effective; effective for longer periods of time; and, therefore, the sunscreen composition need not be reapplied as frequently to maintain effective UV radiation skin protection.
Accordingly, one aspect of the present invention is to provide a stable sunscreen composition that includes a barium stabilizer compound, particularly barium sulfate, capable of photostabilizing a combination of avobenzone and ethylhexyl-p-methoxycinnamate.
Another aspect of the present invention is to provide a sunscreen composition that includes a barium stabilizer compound for a combination of a dimethylbenzoyl derivative UV-A compound, particularly avobenzone; and a UV-B methoxycinnamate derivative, particularly octyl methoxycinnamate, capable of stabilizing the combination of sunscreen agents, and capable of increasing the sunscreen protection factor (SPF) achievable for the combination of sunscreen agents to an SPF of at least 10, particularly 15-25 SPF.
Another aspect of the present invention is to provide a stable sunscreen composition that has a SPF of at least 15, without a sunscreen composition additive selected from the group consisting of benzophenone 3, octocrylene or other substituted dialkylbenzalmalonates or substituted dialkylmalonates. However, in accordance with the present invention any two additional sunscreen agent(s) can be included with the combination of 2-ethylhexyl-p-methoxycinnamate, avobenzone and the barium compound stabilizer, e.g., barium sulfate.
Still another aspect of the present invention is to provide an improved, stable sunscreen composition containing barium sulfate in an amount of at least about 0.1%, preferably at least about 0.5% by weight, more preferably about 1% to about 3% by weight, that increases the effectiveness of a combination of 2-ethylhexyl-p-methoxycinnamate and avobenzone.
The above and other aspects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments.
REFERENCES:
patent: 4387089 (1983-06-01), De Polo
patent: 4489057 (1984-12-01), Welters et al.
patent: 4562067 (1985-12-01), Hopp et al.
patent: 5783173 (1998-07-01), Bonda et al.
patent: 5788954 (1998-08-01), Bonda et al.
patent: 5849273 (1998-12-01), Bonda et al.
patent: 5993789 (1999-11-01), Bonda et al.
patent: 6039935 (2000-03-01), Mohammadi
Sayre, R.M., et al., “Photostability Testing of Avobenzone”, Cosmetics & Toiletries magazine, vol. 114, 85-91 (May 1999).
Tarras-Wahlberg, N., et al., “Changes in Ultraviolet Absorption of Sunscreens After Ultraviolet Irradiation”, The Journal of Investigative Dermatology, vol. 113, 547-553 (1999).
Turro, N.J., Modern Molecular Photochemistry, Menlo Park, Ca: Benjamin/Cummings (1978) pp. 125-126 and 192-193.
Dodson Shelley A.
Marshall O'Toole Gerstein Murray & Borun
The C. P. Hall Corporation
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