Kinetics of di(2-ethylhexyl) phthalate (DEHP) and mono(2-ethylhexyl) phthalate in blood and of DEHP metabolites in urine of male volunteers after single ingestion of ring-deuterated DEHP

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is suspected to induce antiandrogenic effects in men via its metabolite mono(2-ethylhexyl) phthalate (MEHP). However, there is only little information on the kinetic behavior of DEHP and its metabolites in humans. The toxikokinetics of DEHP was investigated in four male volunteers (28-61y) who ingested a single dose (645±20μg/kg body weight) of ring-deuterated DEHP (DEHP-D₄). Concentrations of DEHP-D₄, of free ring-deuterated MEHP (MEHP-D₄), and the sum of free and glucuronidated MEHP-D₄ were measured in blood for up to 24h; amounts of the monoesters MEHP-D₄, ring-deuterated mono(2-ethyl-5-hydroxyhexyl) phthalate and ring-deuterated mono(2-ethyl-5-oxohexyl) phthalate were determined in urine for up to 46h after ingestion. The bioavailability of DEHP-D₄ was surprisingly high with an area under the concentration-time curve until 24h (AUC) amounting to 50% of that of free MEHP-D₄. The AUC of free MEHP-D₄ normalized to DEHP-D₄ dose and body weight (AUC/D) was 2.1 and 8.1 times, that of DEHP-D₄ even 50 and 100 times higher than the corresponding AUC/D values obtained earlier in rat and marmoset, respectively. Time courses of the compounds in blood and urine of the volunteers oscillated widely. Terminal elimination half-lives were short (4.3-6.6h). Total amounts of metabolites in 22-h urine are correlated linearly with the AUC of free MEHP-D₄ in blood, the parameter regarded as relevant for risk assessment.