Roper, C. S., D. Howes, P. G. Blain, and F. M. Williams. A Comparison of the Absorption of a Series of Ethoxylates through Rat Skin In Vitro. Toxic. in Vitro 1998. 12: 57-65. [Reprinted with permission from Elsevier Science]

phenoxyethanol - 00122-99-6; dodecyl decaethoxylate; dodecyl monoethyoxylate

The penetration of phenoxyethanol, dodecyl decaethoxylate and dodecyl monoethoxylate through rat skin was described in in vitro model systems using static cells with aqueous ethanol as receptor or flow-through diffusion cells with tissue culture medium as receptor. Absorption of 2-phenoxyethanol was similar in the static (64%) and flow-through diffusion cells (43%) suggesting that the choice of receptor fluid did not greatly influence prediction of penetration for this compound although the rate of absorption was higher in the static than flow-through cell, which reduced overall losses. A similar absorption was noted if evaporative losses were taken into consideration (static cell, 94%; flow-through diffusion cell, 85%). Dodecyl decaethoxylate absorption was influenced by the choice of receptor fluid, the absorption was 49.4% with aqueous ethanol, but was only 7% with tissue culture medium. However, using tissue culture medium as receptor, more material was located in the stratum corneum and skin than with aqueous ethanol. The highly lipophilic dodecyl monoethoxylate was rapidly absorbed into the lipophilic aqueous ethanol receptor fluid with total penetration of 102% at 8 hours. However, penetration to tissue culture medium was much lower in the flow-through diffusion cell. When stratum corneum, skin and receptor fluid were included in the estimate of penetration, total absorption was 33.3%, which increased to 66% when evaporative losses were considered. In conclusion, absorption profiles reflected the physicochemical properties of the ethoxylates, and the choice of receptor fluid appeared to be the most important factor in the choice of an in vitro model for predicting percutaneous absorption.