title: Effects of silicone emulsifiers on in vitro skin permeation of sunscreens from cosmetic emulsions.
abstract: The effects of different silicone emulsifiers on the in vitro permeation through human skin of two sunscreens (octylmethoxycinnamate, OMC, and butylmethoxydibenzoylmethane, BMBM) were investigated from cosmetic emulsions. The formulations being tested were prepared using the same oil and aqueous phase ingredients and the following silicone emulsifiers: dimethicone copolyol and cyclomethicone (emulsion 1), cetyldimethicone copolyol (emulsion 2), polyglyceryl-4-isostearate and cetyldimethicone copolyol and hexyllaurate (emulsion 3), lauryldimethicone copolyol (emulsion 4), and cyclomethicone and dimethicone copolyol (emulsion 5). The cumulative amount of OMC that permeated in vitro through human skin after 22 h from emulsions 1-5 decreased in the order 2 approximate, equals 1 > 5 > 4 approximate, equals 3 and was about twofold higher from emulsion 2 compared to emulsion 4. As for BMBM, no significant difference was observed in regard to its skin permeation from the emulsions being tested. In vitro release experiments of OMC and BMBM from emulsions 1-5 were performed through cellulose acetate membranes using Franz diffusion cells. Emulsions 1-3 showed an initial slow release of BMBM followed by a fast release phase, while the release of OMC showed a different pattern since the sunscreen was released very rapidly at the beginning of the experiment and then a plateau was observed followed by a second step of fast release. A pseudo-first-order release rate was observed only for BMBM from emulsion 4, while emulsion 5 released very small amounts of both sunscreens during 22 h. These findings could be attributed both to changes in sunscreen thermodynamic activity in the vehicle and to modified interactions between the active ingredient and the formulation components. The results of this study suggest that the type of silicone emulsifier used to prepare sunscreen emulsions should be carefully chosen in order to prevent the percutaneous absorption of sunscreens from these cosmetic formulations.
authors.affiliation: Department of Pharmaceutical Sciences, University of Catania, Viale Andrea Doria 6, I-95125 Catania, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Montenegro
authors.forename: Donatella
authors.initials: D
authors.lastname: Paolino
authors.forename: Giovanni
authors.initials: G
authors.lastname: Puglisi
mesh_terms: D000287:Administration, Topical; D000328:Adult; D000473:Alkanes / Q000493:pharmacokinetics*; D047188:Chalcones / Q000493:pharmacokinetics*; D002934:Cinnamates / Q000493:pharmacokinetics*; D003358:Cosmetics / Q000494:pharmacology; D045703:Emulsifying Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D004655:Emulsions; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D011427:Propiophenones; D012828:Silicones / Q000493:pharmacokinetics / Q000494:pharmacology*; D012869:Skin Absorption / Q000187:drug effects*; D013473:Sunscreening Agents / Q000493:pharmacokinetics*; D014783:Viscosity
chemical_list: D000473:Alkanes; D047188:Chalcones; D002934:Cinnamates; D003358:Cosmetics; D045703:Emulsifying Agents; D004655:Emulsions; D011427:Propiophenones; D012828:Silicones; D013473:Sunscreening Agents; C118580:octylmethoxycinnamate; C049935:avobenzone