Di-n-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) metabolism in a human volunteer after single oral doses.
Level 4 - case-series / case-control
Single-subject pharmacokinetic study (n=1 human volunteer)
PubMed 22820759 · doi:10.1007/s00204-012-0908-1
What was done
A single male volunteer (36 years old, 87 kg) ingested separate oral doses of di-n-butyl phthalate (DnBP) and diisobutyl phthalate (DiBP) at ~60 µg/kg. Urine was continuously collected for up to 48 hours post-dose to identify and quantify key monoester and oxidized metabolites and determine elimination kinetics.
What was found
Most of the administered dose was excreted in urine within the first 24 hours (92.2% for DnBP and 90.3% for DiBP), with <1% excreted on day 2. Simple monoesters were the major metabolites, accounting for 84% of the DnBP dose (MnBP) and 71% of the DiBP dose (MiBP). Side-chain oxidized metabolites accounted for ~8% of the DnBP dose and ~20% of the DiBP dose (predominantly 2OH-MiBP). All metabolites peaked between 2 and 4 hours post-dose. Elimination half-lives were 2.6 hours for MnBP (2.9–6.9 hours for oxidized DnBP metabolites) and 3.9 hours for MiBP (4.1–4.2 hours for oxidized DiBP metabolites).
Why it matters
This study provides baseline human quantitative urinary excretion fractions and kinetic parameters for DnBP and DiBP, confirming that both simple monoesters and secondary oxidized metabolites serve as valid human biomonitoring markers.
Limits
The study was conducted in only a single adult male (n=1), preventing any evaluation of inter-individual variability across sexes, ages, or metabolic phenotypes. It only evaluated single oral bolus exposures rather than chronic, multi-route environmental exposures.
Cited by
- supports Phthalates are cleared by the human body within 12 to 24 hours depending on the compound.