Development of a physiologically-based pharmacokinetic model of 2-phenoxyethanol and its metabolite phenoxyacetic acid in rats and humans to address toxicokinetic uncertainty in risk assessment

• Published in: Regulatory toxicology and pharmacology 2015-11, Vol.73 (2), p.530-543
• Main Authors: Troutman, John A., Rick, David L., Stuard, Sharon B., Fisher, Jeffrey, Bartels, Michael J.
• Format: Article
• Language: English
• Subjects: Acetates - metabolism; Acetates - toxicity; Animals; Body Weight - drug effects; Body Weight - physiology; Dose-Response Relationship, Drug; Dosimetry; Ethylene glycol phenyl ether; Ethylene Glycols - pharmacokinetics; Ethylene Glycols - toxicity; Humans; Models, Biological; Organ Size - drug effects; Organ Size - physiology; PBPK; Pharmacokinetics; Rats; Risk Assessment - methods; Species Specificity; Toxicokinetics; Uncertainty; Uncertainty factors
• ISSN: 0273-2300; 1096-0295
• DOI: 10.1016/j.yrtph.2015.07.012

2-Phenoxyethanol (PhE) has been shown to induce hepatotoxicity, renal toxicity, and hemolysis at dosages ≥ 400 mg/kg/day in subchronic and chronic studies in multiple species. To reduce uncertainty associated with interspecies extrapolations and to evaluate the margin of exposure (MOE) for use of PhE in cosmetics and baby products, a physiologically-based pharmacokinetic (PBPK) model of PhE and its metabolite 2-phenoxyacetic acid (PhAA) was developed. The PBPK model incorporated key kinetic processes describing the absorption, distribution, metabolism and excretion of PhE and PhAA following oral and dermal exposures. Simulations of repeat dose rat studies facilitated the selection of systemic AUC as the appropriate dose metric for evaluating internal exposures to PhE and PhAA in rats and humans. Use of the PBPK model resulted in refinement of the total default UF for extrapolation of the animal data to humans from 100 to 25. Based on very conservative assumptions for product composition and aggregate product use, model-predicted exposures to PhE and PhAA resulting from adult and infant exposures to cosmetic products are significantly below the internal dose of PhE observed at the NOAEL dose in rats. Calculated MOEs for all exposure scenarios were above the PBPK-refined UF of 25. •PhE risk assessment is confounded by species and dose route differences in toxicity.•A PBPK model is presented to address these confounding factors.•Systemic AUC was selected as the appropriate dose metric for risk assessment.•Aggregate human exposure via dermal and oral routes was compared to rat oral NOAELs.•In all cases, the calculated MOEs are above the PBPK-refined total UF of 25.