2-ethylhexyl acrylate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Reason / purpose for cross-reference:

reference to same study

Objective of study:

excretion

metabolism

toxicokinetics

Principles of method if other than guideline:

Two groups of rats were administered either radioactive 14C-2-ethylhexyl acrylate or 14C-2-ethylhexanol, via oral gavage, at equal molar dose levels and equal molar levels of radioactivities. Repetitive blood samples were taken to determine blood 14C concentration-time course and to calculate TK parameters (absorption and elimination half-lives of the total radioactivity in blood, as well as area-under-the-curve (AUC)). During this stage, urine and feces were collected and urinary and fecal excretion of both test materials was also calculated based on the radioactivity of the samples. Expired volatiles and CO2 were also monitored.

GLP compliance:

yes

Remarks:

The study conduct, data, protocol, protocol deviation(s)/amendment(s) if applicable, and final report were inspected by the Quality Assurance Unit

Radiolabelling:

yes

Species:

rat

Strain:

Fischer 344/DuCrj

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- All rats were obtained already cannulated in the jugular vein (JVC)
- Source: Charles River (Kingston, New York)
- Age at study initiation: 9 weeks
- Weight at study initiation: 134-168 g
- Housing: single housed in glass Roth-type metabolism cages
- Diet (e.g. ad libitum): LabDiet Certified Rodent Diet #5002 (PMI Nutrition International, St. Louis, Missouri)
- Water (e.g. ad libitum): municipal water
- Acclimation period: at least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-26
- Humidity (%): 36-87
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

propylene glycol

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
- Dose Preparation
The equal molar levels of both radiolabeled- and unlabeled-test material were added to propylene glycol (PG) for dose preparation. The dose preparation was administered at a target volume of ~5 mL/kg bw; the target radioactivity was ~500 µCi/kg bw.
- Dose Confirmation and Homogeneity of Dose Solutions
Dose confirmation was determined by gas chromatography with a flame ionization detector (GC/FID). LSS analysis of aliquots of the 14C-labeled dose preparation taken from various locations in the vial (top, middle and bottom) was used to confirm the concentration of radioactivity and the homogeneity of the 14C-2-ethylhexyl acrylate and 14C-2-ethylhexanol. The respective dose preparations for Groups 1 to 4, described in study design, had their radiochemical homogeneity determined prior to administration (via LSS). Concentrations of test material-derived radioactivity in blood and excreta were based on analytically determined test material concentrations in dose formulations.
The measured concentration of total test material in each dose solution was 98.5% of the target concentration. The concentration of radioactivity in each of the dose solutions was within 85-100% of the target radioactivity.

Duration and frequency of treatment / exposure:

single administration

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Remarks:

14C-2-ethylhexyl acrylate and 2-ethylhexyl acrylate (0.054 mol/kg bw) (group 1)

Dose / conc.:

70.6 mg/kg bw/day (actual dose received)

Remarks:

14C-2-ethylhexanol and 2-ethylhexanol.(0.054 mol/kg bw) (group 2)

No. of animals per sex per dose / concentration:

3 for time-course blood

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
A dose level of 100 mg/kg body weight (bw) for 2-ethylhexyl acrylate and 70.6 mg/kg bw for 2-ethylhexanol was used in this study. These two dose levels were equimolar (0.054 mol/kg bw) based on the study design. The dose selection was based on the previous metabolism study of 2-ethylhexyl acrylate (Sapota, 1988).

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, air, cage washes,
- Time and frequency of sampling:
Blood: 0.08, 0.17, 0.25, 0.5, 1, 2, 3, 6, 12, and 24h as well as every 24 hours for 7 days post-dosing (approximately 0.1-0.2 mL blood). The blood was oxidized and analyzed for radioactivity via LSS.
Urine: 12- and 24-hour post-dosing followed by 24-hour intervals for the remainder of the study. Urine samples were analyzed for radioactivity via LSS.
Feces: 24-hour intervals up to termination (168 hours post-dosing). Feces samples were analyzed for radioactivity via LSS.
Expired Volatiles: Air was drawn through the cage at approximately 850 ml/minute. The air exiting the cage was passed through charcoal to trap expired volatiles. These charcoal traps were changed at 24-hour intervals. Weighed aliquots of the charcoal were oxidized and analyzed for radioactivity via LSS.
Expired CO2: following the charcoal traps (described above) the expired air was passed through a solution of monoethanolamine:1-methoxy-2-propanol (3:7 v/v) to trap expired CO2 and analyzed for radioactivity via LSS. The CO2 traps were changed at the 6-, 12- and 24-hour time points followed by 24-hour intervals for the remainder of the study. A weighed aliquot of the final cage wash was analyzed for radioactivity via LSS.
Final Cage Wash: following the terminal sacrifice of the animals, a final cage wash (FCW) was performed with water and detergent followed by a final rinse with solvent (acetonitrile). Aweighed aliquot of the final cage wash was analyzed for radioactivity via LSS.
- Terminal Blood Samples and Sacrifice
Termination was 7 days post-dosing. Blood was obtained at sacrifice via cardiac puncture. An aliquot of the blood was directly oxidized and analyzed for radioactivity via LSS.

Statistics:

Descriptive statistics were used, i.e., mean ± standard deviation, when applicable. All calculations in the database were conducted using Microsoft Excel (Microsoft Corporation, Redmond, Washington) spreadsheets and databases in full precision mode (15 digits of accuracy). Certain pharmacokinetic parameters were calculated for blood data, including AUC (area-under-the-curve), Cmax, 1/2Cmax and 1/5Cmax and elimination rate constants, using a pharmacokinetic computer modeling program PK Solutions (v.2.0.6., Summit Research Services, Montrose, Colorado).

Type:

excretion

Results:

Urine (0-168h): 59.37 +/- 5.2 % 2EHA; 65.71 +/- 4.4% 2EH

Type:

excretion

Results:

Feces (0-168h): 20.94 +/- 6.18% 2EHA; 17.28 +/- 2.85 % 2EH

Type:

excretion

Results:

Air (CO2) (0-168h): 12.59 +/- 0.33%; 10.59 +/- 1.02% 2EH

Type:

excretion

Results:

Total recovery (0-168h): 93.86 +/- 1.6% 2EHA; 96.13 +/- 1.23% 2EH

Toxicokinetic parameters:

Tmax: 0.28 +/- 0.21 h

Remarks:

(1st pic) 2-EHA

Toxicokinetic parameters:

Cmax: 18.67 +/- 24.04 µg/g

Remarks:

(1st pic) 2EHA

Toxicokinetic parameters:

Tmax: 6.00 h (2nd pic) 2EHA

Toxicokinetic parameters:

Cmax: 6.42 +/- 0.57 µg/g

Remarks:

(2nd pic) 2EHA

Toxicokinetic parameters:

half-life 1st: 6.23 +/- 0.65 h

Remarks:

2-EHA

Toxicokinetic parameters:

AUC: 249.47 +/- 10.79 µg h g-1)

Remarks:

2EHA

Toxicokinetic parameters:

Tmax: 0.25 +/- 0.22 h

Remarks:

(1st pic) 2EH

Toxicokinetic parameters:

Cmax: 27.14 +/- 8.92 µg/g

Remarks:

(1st pic) 2EH

Toxicokinetic parameters:

Tmax: 6.00 h

Remarks:

(2nd pic) 2EH

Toxicokinetic parameters:

Cmax: 4.47 +/- 0.32 µg/g

Remarks:

(2nd pic) 2EH

Toxicokinetic parameters:

half-life 1st: 5.53 +/- 0.39

Remarks:

2EH

Toxicokinetic parameters:

AUC: 178.43 +/- 16.54

Remarks:

2EH (adjusted according to 100% targeted radioactivity)

Metabolites identified:

no

In-life Parameters

There were no signs of toxicity observed in any animals following oral administration of 14C-2-ethylhexyl acrylate or 14C-2-ethylhexanol.

 

Time-Course Concentration of Radioactivity and Pharmacokinetic Parameters in Blood

Blood concentrations of 2-EHA or 2-EH equivalents from Group 1 and 2 were detectable over the entire study collection interval of 0.08 to 168 hours post-dosing (Table 3A).

The blood time courses from both 2-EHA and EH treated rats (Group 1 and Group 2) demonstrated EHC (enterohepatic recirculation) (Table 3A), indicating that 2-EHA and 2-EH have similar pharmacokinetics in rats after a single oral gavage dose. As shown in Table 3A, the individual blood concentration at earlier time points (0.08 through 2 hours) are variable, especially for animals administered 2-EHA. This difference could be caused by animal variability, especially for the 2-EHA dose group (Table 3A). The Tmax and Cmax differences from Group 1 and Group 2 are due to the animal variability. Based on further pharmacokinetic analyses of the blood time courses, the major pharmacokinetic parameters for both 2-EHA and 2-EH were calculated using PK Solutions (a pharmacokinetic computer modeling program, version 2.0.6., Summit Research Services, Montrose, Colorado) and are summarized in Table 4. As shown in Table 4, pharmacokinetic parameters from individual animals are very similar except first peak Tmax, Cmax and AUC. This difference could be caused by animal variability, especially for the 2-EHA dose group (Table 3A). As the 14C-labeled position in 2-EHA was in the 2-ethylhexyl group (the same position as in 14C-labeled 2-EH), the similarity of PK parameters from both 2-EHA and 2-EH indicated that 2-EHA was quickly hydrolyzed to 2-EH in rats after oral gavage dosage and resulted in similar pharmacokinetics to 2-EH.

Excretion Radioactive Doses of 2-EHA or 2-EH

After a single oral dose of 14C-2-EHA (at 100 mg/kg) or 14C-2-EH (at 70.6 mg/kg) in male rats, the recovery values of radioactive dose in urine, feces, blood, charcoal and CO2 trapping solution collected at different time points, are shown in Table 5. As shown in Table 5, the total average recoveries from both 2-EHA and 2-EH are similar (94% for 2-EHA and 96% for 2-EH). The corresponding recoveries from urine, feces and CO2 trapping solution at each collection time point are very similar for both 2-EHA and 2-EH (Table 5). Especially, the majority of radioactivity of CO2 which was recovered in the first 24 hours post-dosing are similar for both 2-EHA and 2-EH, supporting this hypothesis that 2-EHA was hydrolyzed in the rat to form 2-EH, which was further metabolized to radioactive CO2.

Conclusions:

Blood time-courses from both 2-EHA and 2-EH were similar, with enterohepatic recirculation being observed for both substances. Half-life time (t1/2) for absorption and elimination were also similar, but Tmax and Cmax showed variability amongst animals, especially for 2-EHA. Similar mass balance (urine, CO2 and feces) and metabolite profiles from Cmax (0.17 hr), 1/2Cmax (1 hr) and 1/5Cmax (12 hr) blood samples from rats administered 14C-2-EHA or 14C-2-EH were observed in this current study.

Executive summary:

The compound 2-ethylhexyl acrylate (2-EHA) is expected to undergo rapid ester hydrolysis to form 2-ethylhexanol (2-EH) in vivo. To support this hypothesis of 2-EHA to 2-EH, the absorption and excretion of 14C-2-ethylhexyl acrylate (2-EHA) or 14C-2-ethylhexanol (2-EH) were compared following a single oral dose administration via gavage. Both compounds were labeled at the same 14C-labeled position on the 2-ethylhexyl group. Two groups of 3 male F344/DuCrl rats were dosed at molar equivalents (100 or 70.6 mg/kg body weight of 2-EHA and 2-EH, respectively). The major pharmacokinetic parameters resulting from the blood time-courses and excretion (in urine, feces, volatiles and CO2) were determined.

Blood time courses from both 2-EHA and 2-EH were similar, with enterohepatic recirculation being observed for both substances. Half-life time (t1/2) for absorption and elimination were also similar, but Tmax and Cmax showed variability amongst animals, especially for 2-EHA. Similar mass balance (urine, CO2 and feces) were observed. These study results support a common metabolic pathway with 2-EH after oral gavage administration of 2-EHA or 2-EH in rats.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Objective of study:

metabolism

Principles of method if other than guideline:

Two groups of rats were administered either radioactive 14C-2-ethylhexyl acrylate or 14C-2-ethylhexanol, via oral gavage, at equal molar dose levels. Repetitive blood samples were taken at the Cmax, ½ Cmax, and 1/5Cmax. Comparative metabolite profiling was performed on these collected representative blood samples.

GLP compliance:

yes

Remarks:

The study conduct, data, protocol, protocol deviation(s)/amendment(s) if applicable, and final report were inspected by the Quality Assurance Unit

Test material

Test material information

Constituent 1

Reference substance name:

2-ethylhexyl acrylate

EC Number:

203-080-7

EC Name:

2-ethylhexyl acrylate

Cas Number:

103-11-7

Molecular formula:

C11H20O2

IUPAC Name:

2-ethylhexyl acrylate

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Fischer 344/DuCrj

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- All rats were obtained already cannulated in the jugular vein (JVC)
- Source: Charles River (Kingston, New York)
- Age at study initiation: 9 weeks
- Weight at study initiation: 134-168 g
- Housing: single housed in glass Roth-type metabolism cages
- Diet (e.g. ad libitum): LabDiet Certified Rodent Diet #5002 (PMI Nutrition International, St. Louis, Missouri)
- Water (e.g. ad libitum): municipal water
- Acclimation period: at least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-26
- Humidity (%): 36-87
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

propylene glycol

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
- Dose Preparation
The equal molar levels of both radiolabeled- and unlabeled-test material were added to propylene glycol (PG) for dose preparation. The dose preparation was administered at a target volume of ~5 mL/kg bw; the target radioactivity was ~500 µCi/kg bw.
- Dose Confirmation and Homogeneity of Dose Solutions
Dose confirmation was determined by gas chromatography with a flame ionization detector (GC/FID). LSS analysis of aliquots of the 14C-labeled dose preparation taken from various locations in the vial (top, middle and bottom) was used to confirm the concentration of radioactivity and the homogeneity of the 14C-2-ethylhexyl acrylate and 14C-2-ethylhexanol. The respective dose preparations for Groups 1 to 4, described in study design, had their radiochemical homogeneity determined prior to administration (via LSS). Concentrations of test material-derived radioactivity in blood and excreta were based on analytically determined test material concentrations in dose formulations.
The measured concentration of total test material in each dose solution was 98.5% of the target concentration. The concentration of radioactivity in each of the dose solutions was within 85-100% of the target radioactivity.

Duration and frequency of treatment / exposure:

single administration

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Remarks:

14C-2-ethylhexyl acrylate and 2-ethylhexyl acrylate (0.054 mol/kg bw) (group 3)

Doses / concentrations 2

Dose / conc.:

70.6 mg/kg bw/day (actual dose received)

Remarks:

14C-2-ethylhexanol and 2-ethylhexanol.(0.054 mol/kg bw) (group 3)

No. of animals per sex per dose / concentration:

1

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale:
A dose level of 100 mg/kg body weight (bw) for 2-ethylhexyl acrylate and 70.6 mg/kg bw for 2-ethylhexanol was used in this study. These two dose levels were equimolar (0.054 mol/kg bw) based on the study design. The dose selection was based on the previous metabolism study of 2-ethylhexyl acrylate (Sapota, 1988).

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
See the linked RSS of the same study.

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled (delete / add / specify): blood
- Time and frequency of sampling: Cmax (0.17 hr), 1/2Cmax (1 hr) and 1/5Cmax (12 hr),
- From how many animals: 1
- Method type(s) for identification: Extracts of the selected blood samples were analyzed (profiled) via HPLC separation with radioactivity monitoring (RAM) detection or fraction collection (20 second fractions of eluent collected post-column) followed by liquid scintillation spectrometry (LSS) assay of the fractions
- Limits of detection: 50 dpm

TREATMENT FOR CLEAVAGE OF CONJUGATES (if applicable): no

Results and discussion

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Similar metabolite profiles from Cmax (0.17 hr), 1/2Cmax (1 hr) and 1/5Cmax (12 hr) blood samples from rats administered 14C-2-EHA or 14C-2-EH were observed. No detectable 14C-2-EHA levels were found in any Cmax (0.17 hr), 1/2Cmax (1 hr) or 1/5Cmax (12 hr) blood samples. 14C-2-EH was the only major metabolite observed in all Cmax or 1/2Cmax blood samples.

Any other information on results incl. tables

Metabolite Profiling

The LC/RAM chromatograms of extracts of Cmax (0.17 hr), 1/2Cmax (1 hr) and 1/5Cmax (12 hr) blood samples collected from rats administered with 14C-2- ethylhexyl acrylate or 14C-2-ethylhexanol are shown in Figure 1 and Figure 2, respectively. As shown in Figures 1 and 2, only two peaks (Peak a and Peak b) were detected from the blood samples collected from rats administered either 14C-2-EHA or 14C-2-EH. Peak a eluted at 1.5 min and Peak b eluted at 9.5 min. The retention time of both peaks did not match the retention time of 14C-2-EHA standard (Figure 1A and Figure 2A); however, the retention time of peak b matched the retention time of the 14C- 2-EH standard, supporting that 14C-2-EHA was quickly hydrolyzed to 14C-2-EH in rats after oral gavage administration of 14C-2-EHA. It also should be noted that the slight retention time difference between peak b and 14C-2-EH standard in chromatograms (Figures 1A-1B and Figures 2A-2B) is due to the LC/RAM analysis methods, where both 14C-2-EHA or 14C-2-EH standards were analyzed via HPLC with direct radioactivity monitoring and the blood samples were analyzed via HPLC separation with fraction collection (20 second fractions of eluent collected post-column) followed by liquid scintillation spectrometry (LSS) assay of the fractions. Peak a was a second metabolite related to 14C-2-EH metabolism as it is seen in chromatograms in both Figures 1B, 1C and Figures 2B, 2C. Similar metabolite profiles were obtained from Cmax (0.17 hr) blood samples of 14C-2-EHA and 14C-2-EH [(Figure 1B and Figure 2B); No detectable metabolite peak(s) were found in 1/5Cmax (12 hr) blood samples (Figure 1D and Figure 2D). The 1/2Cmax (1 hr) blood samples (Figure 1C and Figure 2C) had peak b detected in 1/2Cmax (1 hr) blood sample of 14C-2-EH, but not detected in 1/2Cmax (12 hr) blood sample of 14C-2-EHA. Peak b did not appear with either 14C-2-EH or 14C-2-EHA at 1/5Cmax (Figure 1D and Figure 2D). These metabolite profiling results further support the assumption that 14C-2-EHA was hydrolyzed to 14C-2-EH in vivo, resulting in similar pharmacokinetics between 14C-2-EHA and 14C-2-EH as discussed above.

Applicant's summary and conclusion

Conclusions:

Similar metabolite profiles from Cmax (0.17 hr), 1/2Cmax (1 hr) and 1/5Cmax (12 hr) blood samples from rats administered 14C-2-EHA or 14C-2-EH were observed. No detectable 14C-2-EHA levels were found in any Cmax (0.17 hr), 1/2Cmax (1 hr) or 1/5Cmax (12 hr) blood samples. 14C-2-EH was the only major metabolite observed in all Cmax or 1/2Cmax blood samples.

Executive summary:

2-ethylhexyl acrylate (2-EHA) is expected to undergo rapid ester hydrolysis to form 2-ethylhexanol (2-EH) in vivo. To support this hypothesis of 2-EHA to 2-EH, the metabolism of 14C-2-ethylhexyl acrylate (2-EHA) or 14C-2-ethylhexanol (2-EH) were compared following a single oral dose administration via gavage. Male F344/DuCrl rats (one/test compound) were dosed with 2-EHA and 2-EH at molar equivalents (100 or 70.6 mg/kg body weight of 2-EHA and 2-EH, respectively), and blood samples were collected at Cmax (0.17 hr), 1/2Cmax (1 hr) and 1/5Cmax (12 hr) and representative blood samples were profiled. Similar metabolite profiles were observed. No detectable 14C-2-EHA levels were found in any blood samples. 14C-2-EH was the only major metabolite observed in all Cmax or 1/2Cmax blood samples. These study results support a common metabolic pathway with 2-EH after oral gavage administration of 2-EHA or 2-EH in rats.