The metabolism and disposition of ethyl 3-ethoxypropionate in the rat

1. The metabolism and disposition of ethyl 3-ethoxypropionate (EEP) in male Sprague-Dawley rats was studied following single oral gavage at 150 or 1500 mg/kg. The 14C-EEP was rapidly absorbed at both dose levels, and was excreted predominantly as metabolites in the urine within 24 h of administration. 2. The major urinary metabolites of EEP were monoethyl malonate and 3-ethoxypropionate. Other metabolites included malonic acid and the glycine conjugate of 3-ethoxypropionate. Trace amounts of 14C-EEP were detected after both doses. 3. 14CO2 in the expired air accounted for 34% and 20% of the dose at 150 and 1500 mg 14C-EEP/kg, respectively, mostly in the first 24 h following administration. The appearance of 14CO2 indicates extensive oxidation of the molecule, and the lower percentage of 14CO2 at the high dose possibly indicates saturation of an oxidative metabolic pathway. 4. No evidence was found for alkoxyacetic acid metabolites, such as those produced by metabolism of some low molecular weight ethylene glycol ethers.