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Toxicological information

Basic toxicokinetics

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Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Cross-reference
Reason / purpose:
reference to same study
Reference
Endpoint:
dermal absorption in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 Jun 1987 to 10 Dec 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 427 (Skin Absorption: In Vivo Method)
Qualifier:
equivalent or similar to
Guideline:
other: OECD TG 417
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h / 12 h
Type of coverage:
occlusive
Vehicle:
water
Duration of exposure:
48 hr exposure
Doses:
12.5 mg/kg bw (corresponding to 15-20 µCi of radioactivity)
No. of animals per group:
4
Control animals:
no
Details on study design:
TEST SITE
- Area of exposure: interscapularly and as far anteriorly on the back as possible, 4 cm2
- Type of wrap if used: Immediately after dosing, the dosed area was covered with a piece of teflon@ film (4 cm X 4 cm) which was secured to the Stomahesive patch/well with surgical adhesive. The dosed area was then wrapped with veterinary bandaging tape.
- Time intervals for shavings or clipplings: before exposure
Signs and symptoms of toxicity:
no effects
Dermal irritation:
no effects
Absorption in different matrices:
- Skin test site: 32.80 ± 6.16 %
- Carcass: 9.19 ± 0.93 %
- Urine: 27.38 ± 3.06 %
- Cage wash: 0.70 ± 0.28 %
- Faeces: 0.59 ± 0.41 %
- Expired air: 26.53 ± 2.73 % (CO2) + 0.36 ± 0.45 % (volatile organics)
Total recovery:
- Total recovery: 97.54 ± 1.06 %
Key result
Dose:
12.5 mg/kg bw
Parameter:
percentage
Absorption:
ca. 66 %
Remarks on result:
other: 48 hr

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report Date:
1992

Materials and methods

Objective of study:
toxicokinetics
Test guidelineopen allclose all
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Qualifier:
equivalent or similar to
Guideline:
other: OECD TG 427
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
- Source: Sigma Chemical Company, St. Louis, MO (radiolabelled), Epoxy Products Department of The Dow Chemical Company, Freeport, TX (non-radiolabelled)
- Analytical purity: molar purity of 98.3 %, as determined by gas chromatography and infrared analysis (Hermann, 1991)
- Lot/batch No.: 059F9245 (radiolabelled), TB 881212 (non-radiolabelled)
- Radiochemical purity (if radiolabelling): 100 % as determined by high preformance liquid chromatography (HPLC, Analytical Data Sheet 89-397) (upon receipt). The radiochemical purity was evaluated repeatedly throughout the study (Analytical Data Sheets 90-9, 91-5, 90-124, 91-29, 91-33) and ranged from 100 % to 87 %.
- Specific activity (if radiolabelling): 6.3 mCi/mmol (MW 116)
- Locations of the label (if radiolabelling): uniformly labelled 14C-HEA
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories (Kingston, NY; Raleigh, NC)
- Age at study initiation: young adult animals
- Weight at study initiation: approx. 200 g
- Fasting period before study: feed withdrawal approximately 8 hr prior to administration of the 14C-HEA and food was returned about 4 hr post-dosing for all routes of exposure.
- Individual metabolism cages: no data
- Diet (ad libitum): certified rodent chow (Purina Mills Inc., Purina #5002)
- Water (ad libitum): municipal tap water
- Acclimation period: at least one week plus acclimation to glass Roth-type metabolism cages for at least 2 days prior to the administration

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 h / 12 h

Administration / exposure

Route of administration:
dermal
Vehicle:
water
Details on exposure:
TEST SITE
- Area of exposure: interscapularly and as far anteriorly on the back as possible, 4 cm2
- Type of wrap if used: Immediately after dosing, the dosed area was covered with a piece of teflon@ film (4 an X 4 an) which was secured to the Stomahesive patch/well with surgical adhesive. The dosed area was then wrapped with veterinary bandaging tape.
- Time intervals for shavings or clipplings: before exposure


Duration and frequency of treatment / exposure:
48 hr exposure
Doses / concentrations
Dose / conc.:
12.5 mg/kg bw/day
Remarks:
corresponding to 15-20 µCi of radioactivity
No. of animals per sex per dose:
4
Control animals:
no
Details on study design:
After administration or termination of exposure to 14C-HEA, rats from all groups were housed in glass Roth-type metabolism cages. All urine, cage rinse, and feces were collected at specified intervals for up to 48 hr post-dosing or post-exposure and analyzed for radioactivity. In addition, expired organics and 14CO2 were trapped for the 48 hr post-dosing or post-exposure period. Selected samples of urine were analyzed by high performance liquid chromatography (HPLC) to determine 14C metabolic profiles.
The rats were sacrificed 48 hr after administration or exposure to 14C-HEA, and the radioactivity remaining in samples of blood, skin, and the carcass was quantified. For the dermal route of administration, the radioactivity associated with the skin at the dosed site was also determined. in order to determine blood concentration-time profiles, separate groups of animals (different from the groups used to determine the disposition of HEA) were utilized so that expired 14CO2 would not be lost while blood was collected from the animals in the Roth cages.
Radioactivity was quantified with a Beckman LS 3801 or Beckman LS 9000 liquid scintillation Counter (Beckman Instrument Inc., Fullerton, CA).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum, cage washes, bile, 14CO2
- Time and frequency of sampling:
urine (0-12, 12-24 and 24-48 hr post-dosing), faeces (at 24 hr intervals), 14CO2 (0.25, 0.5, 1, 2, 4, 8, and 12 hr post-exposure) (trapped in a mixture of CO2 trapping solution (monoethanolamine: methoxy-2-propanol, 3:7, v/v) and combustion scintillant (Spectrafluor@:methoxy-2-propanol:toluene 12:22:66, v/v)
Blood samples (100 µL) for the 14C plasma and red blood cell time-couse determinations were collected at 0.25, 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 30 and 48 hr after the administration of 14C-HEA by the dermal route.
Statistics:
The half-lives for the CO2 excretion and the plasma radioactivity were determined from the slope of the line obtained by regression analysis of the excretion time-course obtained from each treatment group. Statistical analysis of the data was limited to the calculation of means and standard deviations where appropriate. Pharmacokinetic analysis (calculation of half-lives, AUC's etc.) were carried out using standard methodologies.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:
For the dermal route of administration, about 33 % of the applied dose recovered was associated with the skin or materials used for restricting access to the dermal dose site. Of this 33 %, 11 % of the applied radioactivity was associated with the dosed skin and the remaining 22 % was recovered in the components of the bandage (Stomahesive patch/well, which defined the dosed site, Teflon@ cover and VetRap@). Nine percent of the dose was found in the tissues and carcass.
Details on excretion:
For the dermal route of administration, 27 % of the radioactivity was recovered in the urine and a similar amount of 27 % was recovered as 14CO2. Less than 1 % of the dose was found as volatile organics in the expired air and in the final cage wash and only 0.6 % of the dose was recovered in the faeces.
Following dermal application, nonquantifiable levels of 14CO2 were observed for up to one half hour post application. In addition, there was a lag in peak 14CO2 excretion as compared to the oral and ip routes of administration. This peak occurred at the 12-24 hr collection interval. By 12 hr post-dosing, only 13 % of the dose had been eliminated as 14CO2 in the expired air. The exhalation of 14CO2 derived from 14C-HEA appeared to follow first-order kinetics as a biphasic process, except following dermal administration.
For the dermal route of administration, 38 % of the total radioactivity excreted via the urine was excreted during the 0-12 hr interval and about the same percentage was excreted in the 12-24 hr collection interval.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
HPLC analyses were performed on pooled urine specimens from all treatment groups. Recovery from the HPLC System ranged from 90% to 114%. For all treatment groups, the radiochromatograms of the urinary metabolites contained four major peaks or peak groups of radioactivity. One metabolite could be identified as N-acetyl-S-(carboxylethyl)cysteine by GC/EI/MS. No attempts were made to identify the other three major 14C peaks, however, none of the three peaks were found to correspond to the retention times of HEA or acrylic acid.

Any other information on results incl. tables

The average 14C-HEA doses (mg/kg bw) administered to the dermal treatment group ranged from 84 % to 107 % of target.

No signs of toxicity were observed following dermal administration. In addition, at 48 hr post-dermal application there was an absence of skin irritation.

Since an average of only 66 % of the applied dermal dose was absorbed within 48 hr post-dosing, the dermal absorption of 14C-HEA was a relatively slow process.

The data show, that once systemically available, HEA is rapidly metabolized and eliminated from the body.

Half-lives:

Following the 12.5 mg/kg dermal dose, the half-life for the terminal phase of elimination via 14CO2 was determined to be approximately 17 hr. The half-life for the initial phase of elimination was 4.9.

For the dermal route of administration the half-life of elimination in the urine was approximately 14 hr.

The blood concentration-time profile following dermal administration showed a slow rise in 14C blood concentrations from 15 min post-dosing to peak at 12 hr postdosing, suggesting a slow rate of dermal absorption. However, following dermal absorption the plasma radioactivity concentration-time profile was monophasic suggesting a first order process of elimination. The terminal half-life for the disappearance of plasma 14C activity following dermal dosing was 45 hr. However, this may actually represent the half-life for absorption.

Distribution of radioactivity 48 hr after exposure:

Tissues

Dermal *

12.5 mg/kg bw

Urine

27.38 ± 3.06

Faeces

0.59 ± 0.41

Tissues & carcass

9.19 ± 0.93

14CO2

26.53 ± 2.73

Volatile organics

0.36 ± 0.45

Cage wash

0.70 ± 0.28

Dose site

32.80 ± 6.16

Total

97.54 ± 1.06

* Percent of dose

Values represent Mean ± SD for 4 animals.

Applicant's summary and conclusion