Slow release insect repellents

Details Slow release insect repellents Slow release insect repellents

1993-10-06

2001-01-30

Levy, Neil S. (Department: 1616)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

C424S045000, C424S047000, C424S076300, C424S405000, C424S078030, C424S078240, C424S078360, C424S411000, C514S919000

Reexamination Certificate

active

06180127

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to insect repellents, and in particular to insect repellent formulations having enhanced residual activity.
BACKGROUND OF THE INVENTION
Volatile insect repellents disappear relatively rapidly when applied to the skin. They are also quickly washed away by water, whether fresh or salt containing.
The most prominent insect repellent in use today is N,N′-diethyl toluamide, commonly known as DEET. Other volatile insect repellents are known including ethyl hexanediol; 2-(octylthio)ethanol; dimethyl phthalate; di-n-propyl-2,5-pyridine dicarboxylate; 1,5a,6,9,9a, 9b-hexahydro-4a(4b)-dibenzofuran carboxaldehyde; citronellal; citronellol; geraniol; nerol; and linalool. The formulation of such insect repellents is particularly problematic due to the greasy feel of many of the repellents and especially the effect of DEET in staining clothing, crazing plastics and washing away in humid or rainy weather or when the person using the repellent is participating in water sports such as swimming or fishing. In addition, the lack of retention of insect repellents due to the action of water is also affected by the individual wearer's sweating.
The evaporation of the insect repellent is directly related to the ambient temperature and wind velocity. Approximately 50% of a topically applied dose is absorbed in six hours with peak plasma levels being reached in 1 hour (Lurie et al, Pharmacokinetics of insect repellent N,N-diethyl toluamide. Med. Parazitol., 47, 72, 1979).
Mehr et al, (Laboratory Evaluation of Controlled-Release Insect Repellent Formulations, J. Am. Mosq. Control Assoc., 1,143, 1985) evaluated a number of controlled release formulations of microencapsulated DEET and hydrophilic vinyl polymers such as polyvinylpyrrolidone. The polyvinylpyrrolidone formula was no better than unformulated DEET in repelling mosquitoes.
Reifenrath et al, (Evaporation and Skin penetration characteristics of mosquito repellent formulations. J. Am. Mosq. Control Assoc., 5, 45 1989) tested silicone polymers, acrylate polymers, fatty acids and mixtures of repellents and evaluated evaporation and skin penetration. No differences in evaporation and skin penetration was found between formulations containing the polymers and unformulated DEET or with a mixture of dimethyl phthalate and DEET.
Reifenrath et al, (In vitro skin evaporation and penetration characteristics of mosquito repellents. J. Pharm. Sci. 71, 1014, 1982) showed that the duration of repellent efficacy on man correlated with the time that vapor levels at the surface of the skin exceeded the minimum effective evaporation rates in vitro.
U.S. Pat No. 4,474,081 discloses the use of maleic anhydride/alpha olefin polymers and terpolymers to provide slow release of contact insect repellents when applied to the surface of the skin.
U.S. Pat No. and U.S. Pat. No. 4,774,082 discloses the use of maleic anhydride/alpha olefin polymers and terpolymers to provide slow release of volatile insect repellents when applied to the surface of the skin.
Chemical Abstracts 110, 207847s (1989), discloses mosquito repellent compositions which have an active agent and an oil-soluble, water insoluble acrylate polymer comprising acrylic acid, stearyl methacrylate and isooctyl acrylate.
Ideally, an insect repellent formulation for mammalian use should be non-staining, non-greasy, long lasting, and resistant to washing off from rain, humidity, sweat, fresh waters or ocean waters and reduce penetration of the skin.
SUMMARY OF THE INVENTION
The composition of this invention comprises a copolymer of polyvinyl pyrrolidone and an alkyl group of 4-30 carbons formulated with an insect repellent.
The object of this invention is to provide an insect repellent composition having enhanced residual insect repellent activity comprising: (1) an alkylated polyvinylpyrrolidone; and (2) a volatile insect repellent.
Another object of this invention is to provide an insect repellent composition having enhanced resistance to removal by water, salt water or sweat comprising: (1) an alkylated polyvinylpyrrolidone; and (2) a volatile insect repellent.
Yet another object of this invention is to provide an insect repellent composition having enhanced residual insect repellent activity comprising: (1) an alkylated polyvinylpyrrolidone; (2) a volatile insect repellent and (3) a silicone polymer.
Still another object of the invention is to provide a surface application of an odorant with improved residence time.
Another object of this invention is to provide a matrix containing an odorant which is capable of being sprayed or spread evenly.
Although a great deal of investigation into the cosmetic uses of alkylated polyvinylpyrrolidone copolymers has been carried out, their utility to serve as slow release agents for odorants such as perfumes and insect repellents has not been previously observed.
The compositions of the invention are completely unexpected to give residual activity of insect repellency in light of the previous art. This unexpected characteristic, combined with their known cosmetic appeal of non-greasy and water repellent formulations, provide ideal volatile insect repellent formulations.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Volatile insect repellents which are of value in this invention are those which have the combined characteristics of insect repellency and safety and which can be applied to mammalian skin.
The formulation of this invention contains an alkylated polyvinyl pyrrolidone copolymer and a volatile insect repellent. This formulation is characterized by high residual action, low skin penetration, and high resistance to removal by water. Other volatile materials such as fragrances may be formulated in the compositions of this invention. Such compositions are non-greasy and are easily applied to the skin.
By way of example and not by limitation, insect repellents which are valuable in the invention include: N,N′-diethyl toluamide, commonly known as DEET; ethyl hexanediol; 2-(octylthio)ethanol; dimethyl phthalate; di-n-propyl-2,5-pyridine dicarboxylate; 1,5a,6,9,9a, 9b-hexahydro-4a(4b)-dibenzofuran carboxaldehyde; citronellal; citronellol; geraniol; nerol; and linalool. Other insect repellents recognized in the art, may be used in this invention.
The concentrations of the repellent in the compositions of this invention may be varied, and are limited only by their presence in the composition in such quantities that they will provide effective relief from the targeted insect or insects to be repelled and the concentration of the other ingredients of the formulation.
Thus, the concentration of the insect repellent may be from 1 to 90%, however a range of 1 to 25% is preferred.
Alkylated polyvinylpyrrolidones which may be used include copolymers of polyvinylpyrrolidone and an alpha olefin of chain length of 4 to 30 carbons. Preferred embodiments of this invention are the hexadecene copolymer of polyvinylpyrrolidone (PVP), the eicosene copolymer of PVP and the 1-triacontene copolymer of PVP.
The silicone polymers which are useful in the present invention include dimethicone (Dow Corning 200 Fluids), dimethicone and trimethylsiloxysilicate (Dow Corning 593 Fluid), stearoxy dimethicone (SWS 755 Wax), cyclomethicone (Dow Corning 344 or 345 Fluid, Union Carbide 7158 Fluid, GE SF 1173, 1202 or 1204), polysiloxane (Dow Corning 3225C Fluid), cyclomethicone and dimethicone (Dow Corning X2-1401) and dimethicone (GE SE30, 76 gums, ultrahigh molecular weight dimethicone) and mixtures thereof.
Silicone polymers which are preferred in the invention include polysiloxane (Dow Corning 3225C Fluid) and polydimethylcyclosiloxane (Dow 344 or 345 Fluid).
The silicone polymers may be present in the range of 1 to 60%.
Preservatives which are know in the art to be useful in the present invention include: Quaternium 15 (Dowicil 200), methyl paraben, propyl paraben, dihydroxydimethyl hydantoin, benzyl alcohol, methyl chloroisothiazolinone and methyl isothiazolinone, butyl paraben, imidazolidinyl urea, diazolidinyl urea, disodium ethylenediamine t

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