Oil-in-water emulsion formulation containing free and entrapped hydroquinone and retinol
An oil-in-water emulsion formulation containing hydroquinone and retinol, which comprises an oil-in-water emulsion containing free hydroquinone, hydroquinone entrapped in absorbent micro-agglomerates and/or impregnated in porous microparticles; and retinol-impregnated microparticles.
1. An oil-in-water emulsion formulation containing hydroquinone and retinol, comprising:
(i) an oil-in-water emulsion containing at least 0.01% by weight free hydroquinone; and
(ii) separately dispersed within the oil-in-water emulsion,
(a) one or both of hydroquinone entrapped in micro-agglomerates and hydroquinone-impregnated porous microparticles; and
(b) retinol-impregnated porous microparticles.
2. The formulation of claim 1 , where the total hydroquinone content of the emulsion is from about 0.01% to about 10% by weight.
3. The formulation of claim 2 , where the total hydroquinone content of the emulsion is from about 0.1% to about 5% by weight.
4. The formulation of claim 1 , where at least a part of the hydroquinone is present entrapped in micro-agglomerates.
5. The formulation of claim 1 where the micro-agglomerates comprise a cross-linked polymer selected from the group consisting of a styrene/divinylbenzene crosspolymer, a vinyl stearate/divinylbenzene crosspolymer, a methyl methacrylate/ethylene glycol dimethacrylate crosspolymer, and a lauryl methacrylate/ethylene glycol dimethacrylate crosspolymer.
6. The formulation of claim 5 , where the micro-agglomerates comprise a lauryl methacrylate/ethylene glycol dimethacrylate crosspolymer.
7. The formulation of claim 1 , where at least a part of the hydroquinone is present in hydroquinone-impregnated porous microparticles.
8. The formulation of claim 1 , where the retinol content of the emulsion is from about 0.0001% to about 10% by weight.
9. The formulation of claim 8 , where the retinol content is from about 0.001% to about 5% by weight.
10. The formulation of claim 1 , where the porous microparticles have a weight average diameter less than 50 μm.
11. The formulation of claim 10 , where the porous microparticles have a weight average diameter of about 20 μm.
12. The formulation of claim 1 , where the porous microparticles comprise a cross-linked polymer selected from the group consisting of a styrene/divinylbenzene crosspolymer, a vinyl stearate/divinylbenzene crosspolymer, a methyl methacrylate/ethylene glycol dimethacrylate crosspolymer, and a lauryl methacrylate/ethylene glycol dimethacrylate crosspolymer.
13. The formulation of claim 12 , where the porous microparticles comprise a methyl methacrylate/ethylene glycol dimethacrylate crosspolymer.
14. The formulation of claim 1 , further comprising at least one additional component selected from an antioxidant, a chelating agent, a colorant, a fragrance, and a preservative.
15. A method of simultaneous application of hydroquinone and retinol to the skin, comprising topically applying the formulation of claim 1 .
16. The method of claim 15 , where the total hydroquinone content of the emulsion is from about 0.01% to about 10% by weight.
17. The method of claim 16 , where the hydroquinone content of the emulsion is from about 0.1% to about 5% by weight.
18. The method of claim 15 , where the retinol content of the emulsion is from about 0.0001% to about 10% by weight.
19. The method of claim 18 , where the retinol content of the emulsion is from about 0.001% to about 5% by weight.
20. The method of claim 15 , where at least a part of the hydroquinone is present entrapped in micro-agglomerates.
21. The method of claim 15 , where at least a part of the hydroquinone is present in hydroquinone-impregnated porous microparticles.