Absorption and elimination of a branched-chain alkylpolyethoxylate surfactant in rats

Oral doses (100 mg/kg/day) of a 14C-labelled branched-chain alkylpolyethoxylate ([C 5H 11]2CH 14CH 2O[CH 2CH 2O] 6H; abbreviated [ 14C]A 12E 6) were extensively absorbed from the gastrointestinal tract of rats. During a multiple dosing regime, a proportion of 14C equivalent to one daily dose was excreted each day. This 14C was excreted in urine and faeces in equal proportions; less than 1% of the dose was expired as 14CO 2. Almost all the faecal 14C came from the bile and had undergone enterohepatic circulation. After cutaneous application of [ 14C]A 12E 6 to rats (8 mg, 333 μg/cm 2) under occluded conditions, about 25% of the dose was absorbed, mainly during the first 12 h. After dosing by both routes, the A 12E 6 was biotransformed to several metabolites that were more polar than the parent compound. Less than 15% of the dose was excreted unchanged.