Biochemical studies on phthalic esters. III. Metabolism of dibutyl phthalate (DBP) in animals.

The excretion, distribution and metabolism of DBP were studied in rats. More than 90% of the dose was excreted in the urine within 48 h following intravenous or oral administration, but the faecal excretion was low. Biliary excretion was remarkably higher than that in the faeces when DBP was given orally. No significant retention was observed in organs and tissues at 24 h after dosing. In vitro experiments showed that DBP was hydrolysed very rapidly to MBP by the esterase of rat liver microsome. DBP was found to be a strong inhibitor for the succinate dehydrogenase of rat liver. DBP and its metabolites, MBP and phthalic acid, did not produce any striking effect upon hepatic and serum enzyme activities in vitro. Urinary metabolites of orally ingested DBP were investigated in 3 species, namely, rats, hamsters and guinea pigs. MBP was a common major metabolite in all 3 species. A further increment was apparently excreted as the glucuronide in the rat, hamster and guinea pig together with a small amount of phthalic acid and unchanged DBP. Omega- or omega-1 oxidation products of MBP were also detected in the urine.