Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Patent
1996-08-12
1999-02-09
Dodson, Shelley A.
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
424 60, 424400, 424401, 514241, A61K 742, A61K 3153, A61K 700
Patent
active
058690301
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to new physical forms of UV absorbers and to their use in sunscreen compositions which, in turn, are useful, in particular, for the protection of human skin.
It has long been known that prolonged exposure to that UV radiation which reaches the surface of the earth can lead to the formation of erythemas or light dermatoses, as well as to an increased incidence of skin cancers or accelerated skin aging.
Various sunscreen formulations have been proposed which include a material which is intended to counteract UV radiation, thereby inhibiting the said undesired effects on the skin.
A great number of compounds has been proposed for use as UV protectants in sunscreen formulations, especially soluble organic UV absorbers and insoluble micronised inorganic compounds, in particular zinc oxide and titanium dioxide.
With respect to the use in sunscreen formulations of soluble organic UV absorbers, they have disadvantages that their effectiveness as UV protectants in terms of SPF (Sun Protection Factor) in a sunscreen formulation is often too low for commercial purposes; as a result of their solubility, they exhibit relatively high allergenic potential; and that as a result of intrinsic photochemical lability, the duration of the protective effect is often too low.
The high specific weight of insoluble inorganic compounds, such as zinc oxide and titanium dioxide leads to a reduced stability of formulations containing them. Moreover, such inorganic compounds have been claimed to generate toxic radicals under the influence of light ("Redox Mechanisms in Heterogeneous Photocatalysis", Serpone et al, Electrochemistry in Colloids and Dispersions, Editors Mackay and Texter, VCH Publishers Inc., New York 1992).
It has now been found, surprisingly, that micronised, insoluble organic UV absorbers, when used in sunscreen formulations, provide excellent UV protection and have at least as high an SPF rating as corresponding sunscreen formulations containing a known inorganic UV absorber. Unlike the latter UV absorbers, micronised, insoluble organic UV absorbers show no tendency, under the influence of light, to generate radicals which could damage or sensitise human skin. Moreover due to their insolubility in sunscreen formulations, micronised, insoluble organic UV absorbers do not penetrate the skin so that they are not able to exert any undesired allergic or sensitising effects on the skin.
Accordingly, the present invention provides, as a first aspect, a composition of matter, which is especially suitable for use in pharmaceutical or cosmetic applications, comprising a micronised, insoluble organic UV absorber, with the exclusion of o-hydroxyphenyl-s-triazines having the formula: ##STR1## in which R.sub.a, R.sub.b and R.sub.c, independently, are hydrogen, halogen, C.sub.1 -C.sub.18 alkyl or C.sub.1 -C.sub.18 alkoxy, and R.sub.d and R.sub.e, independently, are hydrogen or C.sub.1 -C.sub.18 alkoxy with the provisos that one of R.sub.d and R.sub.e is always C.sub.1 -C.sub.18 alkoxy, and that, if R.sub.b, R.sub.c, R.sub.d and R.sub.e are each C.sub.1 -C.sub.18 alkoxy, then R.sub.a is halogen, C.sub.1 -C.sub.18 alkyl or C.sub.1 -C.sub.18 alkoxy.
Preferably, the insoluble organic UV absorber has a mean particle size in the range of from 0.02 to 2, more preferably from 0.05 to 1.5, especially from 0.1 to 1.0.mu..
The insoluble organic UV absorber may be converted into the desired particulate size state by conventional methods, e.g. by grinding the insoluble organic UV absorber, in coarse particle form, in the presence of suitable grinding aids and using known grinding apparatus, e.g., a jet, ball, vibration or hammer mill, preferably a high speed stirring mill or impact mill, especially a rotating ball mill, vibrating mill, tube mill or rod mill.
Preferably, the grinding is conducted in the presence of 0.1 to 30%, preferably 0.5 to 15% by weight, based on the micronised, insoluble organic UV absorber, of a grinding aid such as an alkylated vinylpyrrolidone polymer, a vinylpyrrolidone-vinylacetate copolym
REFERENCES:
patent: 3004896 (1961-10-01), Heller et al.
patent: 4514383 (1985-04-01), Murray et al.
patent: 4617390 (1986-10-01), Hoppe et al.
Redox Mechanisms in Heterogeneous Photocatalysis, Serpone et al.
Dumler Walter
Frankhauser Peter
Luther Helmut
Ciba Specialty Chemicals Corporation
Dodson Shelley A.
Mansfield Kevin T.
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