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

Oral doses (100 mg/kg/day) of a 14C-labelled branched-chain alkylpolyethoxylate [( C5H11]2CH14CH2O[CH2CH2O]6H; abbreviated [14C]A12E6) 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 14CO2. Almost all the faecal 14C came from the bile and had undergone enterohepatic circulation. After cutaneous application of [14C]A12E6 to rats (8 mg, 333 micrograms/cm2) under occluded conditions, about 25% of the dose was absorbed, mainly during the first 12 h. After dosing by both routes, the A12E6 was biotransformed to several metabolites that were more polar than the parent compound. Less than 15% of the dose was excreted unchanged.