54 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS IIII •VVVoV e4 •- V V V V '•.. V --ooVVVVV e4 e4 e4 V V V V V

PERCUTANEOUS ABSORPTION OF ANIONIC SURFACTANTS 55 Turnover of [•4C] surfactants in the rat The rate and route of excretion of •4C from intraperitoneally adminis- tered [•C] surfactant solutions were the same as that from subcutaneously administered solutions. The recoveries are given in Table II. Table II. Recoveries of xaC fi'om rats after injection with [•aC] surfactants [•C] surfactant* Dose % Applied dose [tCi (rag) CO2 Urine Faeces Carcass Soaps SDS SDI DOBS Clo: o C12: o C14: o C16: o C18: o 7.25 0.12 575_5 0.1 0.1 374-6 10.49 0.13 65_4-7 0.1 0.1 304-7 8.13 0.15 5 4-3 2.1 4-1.2 0.1 85 4-9 7.74 0.17 21 4-4 0.1 0.1 71 4-8 8.59 0.18 384-9 0.1 0.1 564-16 18.60 3.64 1.54-0.4 774-4 2.64-0.7 154-3 8.29 4.90 804-7 2.74-0.2 1.74-0.5 124-5 8.69 1.02 0.1 78 4-4 1.5 4-0.6 22 4-5 Each result is the mean from six animals 4- SD--three animals injected intraperitoneally and three animals subcutaneously. For the sodium soaps the collection time was 6 h after injection and for the other surfactants 24 h. * All [x4C] surfactants were labelled with x•C in the 1-alkyl position and were sodium salts. These results showed that at 6 h after administration, the Cx0:0 and Cx, 0 soaps were readily metabolized and the main route of excretion was as 1•CO, The Cx•: 0 soap was readily incorporated into the body and the 1•C excretion was slow. The Cx0: 0 and Cxs: 0 soaps showed some metabolism with subsequent •CO2 excretion but most of the 1•C was recovered in the carcass at 6 h. For both the [x4C] SDS and the [1•C] DOBS most of the administered x•C was recovered in the urine at 24 h after dosing. The [x•C] SDI was metabolized and most of the dose was recovered as 1•CO• at 24 h indicating the breakdown of the isethionate ester link. From the results the route of excretion of x•C surfactant giving the most sensitive indication of percutaneously absorbed surfactant was indicated. Absorption of [14C] soaps through rat skin in vivo The amount of the [1-1•C] labelled soaps penetrating through 7.5 cm" of treated skin was calculated from the levels of 1•C recovered in the