Registration Dossier

Toxicological information

Basic toxicokinetics

Currently viewing:

Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1989
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Remarks:
No details about environmental conditions but similarities with the study in male rats are presumed.

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Pharmacokinetics of ethylene glycol. I. Plasma disposition after single intravenous, peroral, or percutaneous doses in female Sprague-Dawley rats and CD-1 mice
Author:
Frantz SW, Beskitt JL, Grosse CM, Tallant MJ, Dietz FK, Ballantyne B
Year:
1996
Bibliographic source:
Drug Metab Dispos 24: 911-921
Reference Type:
publication
Title:
Pharmacokinetics of ethylene glycol II. Tissue distribution, dose-dependent elimination, and identification of urinary metabolites following single intravenous, peroral or percutaneous doses in female Sprague-Dawley rats and CD-1® mice
Author:
Frantz SW, Beskitt JL, Grosse CM, Tallant MJ, Dietz FK, Ballantyne B
Year:
1996
Bibliographic source:
Xenobiotica 26: 1195-1220
Reference Type:
review article or handbook
Title:
Toxicological profile for ethylene glycol
Author:
ATSDR
Year:
2010
Bibliographic source:
US Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia

Materials and methods

Objective of study:
toxicokinetics
Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Deviations:
no
GLP compliance:
not specified
Remarks:
GLP statements are usually not mentioned in publications in journals

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
unlabelled: purity > 99.9%, source: Union Carbide, Hahnville, LA, USA
Radiolabelling:
yes
Remarks:
[1,2-14C]-ethylene glycol from Sigma Chemicals, specific activity 3.6 mCi/mmol radiochemical, purity: 99.2% (analysed by GC)

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
female
Details on test animals and environmental conditions:
Source: Harlan Sprague-Dawley, Inc., Indianapolis, USA
age: 10-11 weeks (180-250 g bw)
acclimatisation: 2 days

Administration / exposure

Route of administration:
other: oral, dermal or intravenous (i.v.)
Vehicle:
other: see details
Details on exposure:
Oral
Gavage; vehicle water, rats were fasted for 15-16 h prior to application; concentration in vehicle 0.5, 20, 30, 40, 50%, respectively; total volume applied: 2 ml/kg bw; analytical control of dose via liquid scintillation spectrometry
Dermal
Preparation of test site not specified; dose 10 or 1000 mg/kg bw undiluted or 1000 mg/kg bw 50% w/w water solution (15-25 μCi/animal); volume applied: 2 ml/kg bw applied to 1 cm² in the interscapular region of the back by special syringe method; exposure period: 6 hours under occlusive covering; then occlusive covering was removed and any unabsorbed test substance was washed from the dose site with water-wettened, cotton-tipped applicators; replacement with fresh covering for the total 96-hour test period
i.v.
Application via indwelling jugular cannula which was surgically implanted 48 hours prior to dose administration; target dose 10 or 1000 mg/kg bw, corresponding to 5 μCi/animal; vehicle physiological saline; total volume applied: 2 ml/kg bw



Duration and frequency of treatment / exposure:
once
Doses / concentrations
Remarks:
Doses / Concentrations:
Oral dose: 10, 400, 600, 800, 1000 mg/kg bw (10-15 μCi/ animal)
Dermal: 10 or 1000 mg/kg bw undiluted or 1000 mg/kg bw 50% w/w water solution
i.v.: 10 or 1000 mg/kg bw
No. of animals per sex per dose:
4/dose/route
Control animals:
no
Details on study design:
Dose selection rationale: NOAEL/LOAEL in repeated dose toxicity studies
Details on dosing and sampling:
Sampling time
Blood (via jugular cannula): 0.5, 1, 2, 4, 8, 12, 18, 24, 36, 48, 72, and 96 h after dosing.
Exceptions: Additional blood samples at 5 and 15 min post-dosing for the intravenous application. For the 400, 600 and 800 mg/kg bw gavage groups blood sampling only at 24, 36, 48, 72, and 96 h after dosing.
Urine and faeces samples: 12, 24, 36, 48, 72, 96 h post dosing
Expired 14CO2: air flow through metabolism cages ca. 500 ml/min; expired CO2 trapped in 12-24-hour intervals using solutions of 2-methoxymethanol:ethanolamine (7:3)

Samples for distribution of 14C-activity
Urine, faeces, plasma, 14CO2-trap solution sampled at indicated timepoints.
Total exsanguination via cardiac puncture 96 hours post-dosing.
Faeces and tissues were prepared as 33% water homogenates.
Radioactivity of these samples was analysed by liquid scintillation spectrometry.
Skin sample for dermal study: dosed area together with the skin around the periphery (approximately 1 cm further); sample pulverized at liquid nitrogen temperature, radioactivity of aliquots counted directly as suspension by liquid scintillation spectrometry.

Analysis of unmetabolized ethylene glycol
Plasma samples (timepoints see above) remaining after radioanalysis were pooled in equal volumes and derivatized with phenylboronic acid (PBA). PBA-derivatized ethylene glycol was analysed using capillary GC with a Mass Selective Detector and was identified using Selective Ion Monitoring techniques. Limit of quantitation: ca. 1 ng/µl

Profiles of ethylene glycol metabolites in plasma
Separate groups to obtain larger plasma volumes: 2 rats/interval
Studied doses: 10 and 1000 mg/kg bw via gavage
Sampling times: exsanguination via cardiac puncture at 2, 4, 6, 8, 10 and 12 h after administration
Preparation of plasma samples via ultrafiltration using Centricon-10 concentrators
Analysis of plasma samples: HPLC with ion exchange column, detection with in-line radioactivity flow monitor and differential refractive index detector; analyzed metabolites: ethylene glycol, glycolic acid (glycolate), glycolaldehyde, glyoxylic acid (glyoxylate), oxalic acid (oxalate); glyoxalate and glyoxal are not distinguishable in this HPLC system
Limit of quantitation: 33 ng/100 µl of injected plasma filtrate

Profiles of ethylene glycol metabolites in urine
Selected urine samples from 4 rats/dose were analysed for metabolites: selection criterium was the appearance of 14C-activity in total urine.
Analyzed samples, application mode and dose groups:
Analysis of urine samples: HPLC with ion exchange column, detection with in-line radioactivity flow monitor and differential refractive index detector
Analyzed metabolites: ethylene glycol, glycolic acid (glycolate), glycolaldehyde, glyoxylic acid (glyoxylate), glyoxal, oxalic acid (oxalate)
Limit of quantitation: ca. 1 µg ethylene glycole/ml urine; ca. 2 µg metbolite/ml urine

Pharmacokinetic evaluations
Pharmacokinetic data analysis was based on semilogarithmic plots for concentrations of both total radioactivity and unchanged ethylene glycol in plasma versus time.
Analysis of elimination and transfer of 14C- ethylene glycol between compartments: mean plasma 14C concentrations were used initially to fit one-, two- or three-exponential equations. Both were assumed to be first-order processes.
Plasma concentration-time data:
14C-concentrations after intravenous and dermal application, and ethylene glycol concentration after oral administration: described by a biexponential equation of the form: Ct = AeExp-alpha t + Be Exp-beta t.
14C-concentrations after oral administration described by a triexponential equation and ethylene glycol concentration after intravenous administration described by a monoexponential equation.
Parameters estimated based on mean plasma concentration values:
beta: rate constant for terminal disposition
AUC: area under the curve
Vdss: apparent volume of distribution at steady state
Cl oral: clearance of ethyleneglycol after oral doslng
Cl total = [dose : AUC] x 1000 µg/mg
MRT: mean residence time
t½: half-times of elimination
U EG: % administered dose excreted unchanged via urine (0-24 h)
F: fraction of the parent dose absorbed, or its bioavailable dose
Cmax: max plasma concentration
tmax: time to maxlmum concentration



Statistics:
means and standart deviation

Results and discussion

Main ADME results
Type:
other: see detailed text below

Toxicokinetic / pharmacokinetic studies

Details on absorption:
see detailed text below
Details on distribution in tissues:
see detailed text below
Details on excretion:
see detailed text below

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
see detailed text below

Bioaccessibility

Bioaccessibility testing results:
see detailed text below

Any other information on results incl. tables

Absorption

Oral route

Results presented in Table 1 have shown that bolus gavage doses of 10 or 1000 mg/kg bw ethylene glycol (EG) were rapidly and almost completely absorbed in female rats, with a bioavailable fraction of 92%. Uptake and elimination of EG from plasma was biexponential; elimination rates and t1/2 beta values were of similar duration between dose levels. Overall, a linear pharmacokinetic relationship for parent EG was apparent for both oral dose levels. Data on oral doses of 400, 600 or 800 mg/kg bw (not shown in Table 1) suggested that plasma 14C elimination is independent of dose in this range.

Dermal route

In contrast to the oral route, the absorption of cutaneously applied EG is comparatively slow in female rats (see Table 1). EG has a bioavailability of only 25%. Total absorption of radioactivity varied between 26-32% (see Table 2).

Total recoveries

Recoveries of total radioactivity were within 83 to 92% with exception of the 10 mg/kg bw dermal application with a reduced recovery of 42% only (see Table 2).

Tissue distribution of 14C-activity (see Table 2 and 3)

Intravenous and oral route (10, 1000 mg/kg bw):

Total tissue recovery of 14C accounted to 5.3 and 5.7% at the low dose. At the high dose there was a nearly twofold decrease to 3.3 and 2.2%. Concentrations of 14C in individual tissues showed a dose-dependence being about two orders of magnitude lower at the low dose compared to high dose tissue values. Tissue/plasma ratios > 1.0 were calculated for liver, kidney, and lung, indicating a greater presence of 14C in these tissues than would be accounted by plasma perfusion alone.

Dermal route (10, 1000 mg/kg bw, undiluted ethylene glycol):

The distribution of 14C to tissues showed similar disposition profiles to those observed after i.v. and p.o. dosing. Tissue/plasma ratios > 1.0 were calculated for: liver, kidney, and pelt at 10 mg/kg bw, for liver, kidney, lung and pelt at 1000 mg/kg (undiluted), and for liver and pelt at 1000 mg/kg bw (aqueous dilution), indicating a greater presence of 14C in these tissues than would be accounted by plasma perfusion alone.

Excretion (see Table 2, 4 and 5)

Total excretion of radioactivity

14C-activity was recovered from urine, faeces and as 14CO2 in exhaled air in percentages varying for different application routes and doses.

Intravenous and oral route (10, 1000 mg/kg bw): 10 mg/kg bw: major excretion route: exhalation 44-48%; urine: 25%; faeces: 2.0-2.8%. 1000 mg/kg bw (values for i.v. and p.o. route, respectively): major excretion route: urine 45%, 35%; exhalation 29%, 28%; faeces: 5.4%, 4.4%.

Oral route (400, 600, 800 mg/kg bw): At 400 mg/kg bw excretion via exhalation and urine accounted to approximately equal amounts. In the dose range up to 800 mg/kg bw there was a dose-dependent increase of urinary excretion being accompanied by a decrease of 14CO2 exhalation. This points to saturation of oxidative metabolic pathways.

Dermal route (10, 1000 mg/kg bw, undiluted ethylene glycol): 10 mg/kg bw: major excretion route: exhalation 13.1%; urine 8.2%; faeces 1.1%. 1000 mg/kg bw: exhalation 11.4%; urine 7.6%; faeces 1.4%. Dermal route (1000 mg/kg bw, undiluted ethylene glycol): major excretion route: exhalation 9.3%; urine 4.4%; faeces 0.5%.

Time course of excretion of radioactivity and metabolites

Intravenous and oral route (10, 1000 mg/kg bw): Elimination profiles for total radioactivity were similar in both time-course and amount of the dose excreted for both application routes and for each dosage, indicating that the majority of the oral doses were absorbed. For both routes, at the low dose excretion of radioactivity was mainly via exhalation as 14CO2. In contrast, at the high dose urinary excretion was the dominant route. Urinary excretion: majority of 14C excreted within 12 h, urinary excretion virtually complete within 24-36 h post-dosing. At the high 1000 mg/kg-dose a higher percentage was excreted via urine (i.v. 45%, p.o. 35%) than after the low 10 mg/kg-dose (25%).

10 mg/kg bw: Urinanalysis of metabolites yielded a similar pattern for the low dose for both application routes with unchanged ethylene glycol accounting to ca. 93% of total 14C during the first 12 hours. Glycolic acid (ca. 5%) and oxalic acid (<1%) were found as minor metabolites. 1000 mg/kg bw: During the 12-24 h interval excretion of unchanged ethylene glycol accounted to 53% (i.v.) and 65% (p.o.) besides glycolic acid (46% and 35%). Oxalic acid was found only in minor amounts (<1%).

Exhalation of 14CO2: There was still a slow increase of cumulative exhaled 14CO2 at the end of the 96-h observation period. Within this interval the majority of 14CO2 was exhaled within the first 24 h. Overall levels were inversely related to dose (44-48% at the low dose, 28% at the high dose).

Dermal route (10, 1000 mg/kg bw, undiluted ethylene glycol): Elimination profiles for total radioactivity for both doses showed a continuous increase of excretion during the 96-h observation period up to a final excretion of 8-10% of the dose via urine and of 13% via exhalation. Total excretion was lower than after i.v. or p.o. application. However, taking the low dermal penetration into account, excreted relative amounts were comparable with excretion percentages after i.v. or p.o. dosing. In the urine fractions unchanged ethylene glycol was detected as the major component (87-100%). Dermal route (1000 mg/kg bw, 50 % aqueous dilution of ethylene glycol): Measurable excretion of 14C was retarded until 24 h post-dosing. There was a continuous increase during the 96-h observation period until final levels of 5% in urine and 9% in exhaled air. Radioactivity in urine accounted to 100% to unchanged ethylene glycol.

Applicant's summary and conclusion

Conclusions:
No bioaccumulation potential based on study results.
Ethylene glycol is very rapidly and almost completely absorbed after oral doses but dermally-applied EG was slowly and rather poorly absorbed; oxidative metabolite pathways appeared to be saturated at high oral doses; linear pharmacokinetic relationship was apparent for the oral route.
Executive summary:

This study was comparable to OECD guideline 417. 14C-ethylene glycol was administered to female Sprague-Dawley rats (n=4 per group) intravenously, orally or dermally in single doses ranging from 10 – 1000 mg/kg bw. Pharmacokinetic investigations of the fate of ethylene glycol included absorption from the gastrointestinal tract, skin penetration, tissue distribution, identification of metabolites in urine, and pathways and kinetics of excretion.

Results have shown that gavage doses of 10 or 1000 mg/kg bw ethylene glycol (EG) were rapidly and almost completely absorbed in female rats, with a bioavailable fraction of 92%. Uptake and elimination of EG from plasma was biexponential; elimination rates and t1/2 beta values were of similar duration between dose levels. Overall, a linear pharmacokinetic relationship for parent EG was apparent. In contrast to the oral route, the absorption of cutaneously applied EG is comparatively slow in female rats. EG has a bioavailability of only 25%. Total dermal absorption of radioactivity varied between 26-32%. Relative recoveries of 14C in tissues and carcass were higher at the 10 mg/kg bw p.o. and i.v. dose in comparison to the 1000 mg/kg bw dose, whereas individual 14C concentrations in tissues increased dose-dependently. Storage in tissue accounted to total amounts of ca. 2-6 % of the dose after 96 hours. Extensive metabolism via oxidative pathways is indicated by the high amounts of 45-49 % of the dose exhaled as 14CO2 at 10 mg/kg. Expiration of 14CO2 diminishes to 30 % as the dose increases to 1000 mg/kg bw. Parallel to the decrease of excretion via exhalation urinary excretion increases from 25% to 36-46% of the dose. Urinary excretion profiles show unchanged ethylene glycol as the main source of 14C besides glycolate as the major urinary metabolite and minor amounts of oxalate (<1%). Only minor amounts of 14C are both excreted in the faeces (ca. 2-5%) and remain in the carcass (ca. 5-9 %).

Conclusions: Ethylene glycol is very rapidly and almost completely absorbed after oral doses but dermally-applied EG was slowly and rather poorly absorbed; oxidative metabolite pathways appeared to be saturated at high oral doses; linear pharmacokinetic relationship was apparent for the oral route.