Benzyl acetate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Studies on Benzyl Acetate III The Percutaneous Absorption and Disposition of [Methylene-14C]Benzyl Acetate in the Rat.

Author:

Chidgey, M.A.J., Kennedy, J.F., Caldwell, J.

Year:

1987

Bibliographic source:

Fd. Chem. Toxic. Vol 25 (7), pp 521 - 525

Materials and methods

Objective of study:

other: absorption and distribution

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Toxicokinetic investigations using percutaneous absorption in the rat, in vivo, with radiolabelled test material

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Benzyl acetate

EC Number:

205-399-7

EC Name:

Benzyl acetate

Cas Number:

140-11-4

Molecular formula:

C9H10O2

IUPAC Name:

benzyl acetate

Details on test material:

- Name of test material (as cited in study report): Benzyl Acetate
- Radiochemical purity (if radiolabelling): >96%
- Specific activity (if radiolabelling): 53mCi/mmol

Specific details on test material used for the study:

- Name of test material (as cited in study report): Benzyl Acetate
- Radiochemical purity (if radiolabelling): >96%
- Specific activity (if radiolabelling): 53mCi/mmol

Radiolabelling:

yes

Remarks:

>96% radiochemical purity

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Oxford Laboratory Animal Co. (Oxford)
- Age at study initiation: Not documented
- Weight at study initiation: 200g
- Fasting period before study: The animals were not fasted - they were allowed access to food and water ad libitum throughout the experiments.
- Housing: Not documented
- Individual metabolism cages: Not documented
- Diet (e.g. ad libitum): Oxoid 41B Pellets ad libitum
- Water (e.g. ad libitum): Water ad libitum
- Acclimation period: Not documented

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Not documented
- Humidity (%): Not documented
- Air changes (per hr): Not documented
- Photoperiod (hrs dark / hrs light): Not documented

IN-LIFE DATES: From: To: Not documented

Administration / exposure

Route of administration:

dermal

Vehicle:

other: Applied neat or as a 50% (v/v) solution in ethanol.

Details on exposure:

- Area of exposure: The animals backs were shaved. The area of application varied. It was 6.25, 12 and 18cm2
- % coverage: Not documented
- Type of wrap if used: The dose was applied to a layer of Kleenex tissue (single or double ply) placed on a piece of aluminium foil of an appropriate area. The dressing was positioned on the shaven area with the tissue next to the skin and was held in place with polyethylene tape which was wrapped around the body and further occluded the application site.
- Time intervals for shavings or clipplings: At the beginning of each experiment animals were shaved.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The shaven areas were washed twice with lint lint swabs wetted with ethanol and the animals were immediately returned to the metabolism cages.
- Time after start of exposure: 6 hours following exposure

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 100, 250 and 500 mg/kg body weight.
- concentration (if solution): 100% or 50% (v/v) solution in ethanol.

VEHICLE
- Justification for use and choice of vehicle (if other than water): Ethanol if applied as a dilution
- Amount(s) applied (volume or weight with unit): Not documented
- Concentration (if solution): Not documented
- Lot/batch no. (if required): Not documented
- Purity: Not documented

USE OF RESTRAINERS FOR PREVENTING INGESTION: no

Duration and frequency of treatment / exposure:

The animals were exposed for 6 hours.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 mg/kg bw (total dose)

Doses / concentrations 2

Dose / conc.:

250 mg/kg bw (total dose)

Doses / concentrations 3

Dose / conc.:

500 mg/kg bw (total dose)

No. of animals per sex per dose / concentration:

Not documented

Control animals:

not specified

Positive control reference chemical:

Not required

Details on study design:

- Dose selection rationale: Not documented
- Rationale for animal assignment (if not random): Not documented

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, blood
- Time and frequency of sampling:
- Other: For the tissue distribution study, the liver, heart, lung, brain, kidney, gut wall and gut contents were placed in water and homogenized and levels of 14C were determined following combustion. The skin and subcutaneous fat form the application site and surrounding area were also removed and assayed for radioactivity using alkaline digestion method used to determine levels of residual 14C in carcasses.

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled (delete / add / specify): urine
- Time and frequency of sampling: Not documented
- From how many animals: (samples pooled or not) Not documented
- Method type(s) for identification: TLC and HPLC.
- Limits of detection and quantification: Not documented
- Other: The metabolites were identified by comparison of their chromatographic mobilities and colour reactions with those of authentic samples of the metabolites.

TREATMENT FOR CLEAVAGE OF CONJUGATES (if applicable): No information provided

Statistics:

The interdependence of sets of data was assessed by means of the Spearman rank correlation and statistical comparison of data was performed with Student's unpaired t-test.

Results and discussion

Main ADME results

Main ADME results 1

Type:

absorption

Results:

The absorption of the compound was unaffected by dose size, area of application or the use of ethanol as a vehicle. In all cases, a significant proportion of the dose (28-48%) was recovered from the application site after 6 hr.

Main ADME results 2

Type:

absorption

Results:

A twofold increase in the concentration on the skin resulted in an approximately twofold increase in the amount absorbed per unit area of skin.

Main ADME results 3

Type:

metabolism

Results:

hippuric acid was the major metabolite of the topically applied compound, accounting for c. 95% of urinary 14C.

Main ADME results 4

Type:

metabolism

Results:

Also present were much smaller amounts of benzoyl glucuronide, benzoic acid and benzylmercapturic acid, each accounting for c. 1-2% of urinary radioactivity.

Main ADME results 5

Type:

metabolism

Results:

the proportions of the administered dose excreted as hippuric, benzoic and benzylmercapturic acids were not significantly influenced by dose size.

Main ADME results 6

Type:

distribution

Results:

approximately 79% of the administered dose was recovered

Main ADME results 7

Type:

distribution

Results:

levels of radioactivity in all the organs examined were lower in the animals killed 24 hr after administration of the test compound.

Main ADME results 8

Type:

distribution

Results:

Recovery of 14C in the skin and subcutaneous fat of the application site and surrounding area accounted for 3.7% of the dose immediately after the removal of the dressings and this had declined to 1.2% 24hr after dosing.

Main ADME results 9

Type:

distribution

Results:

Radioactivity remaining in the carcasses of the rats accounted for < 4% of the administered dose.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The extent of absorption of the test compound was assessed at three dose levels, two of which were applied to different areas of skin. The absorption of the compound was unaffected by dose size, area of application or the use of ethanol as a vehicle. In all cases, a significant proportion of the dose (28-48%) was recovered from the application site after 6 hr. Most of this (c. 96%) was found on the dressings with the remainder in the skin washings. Most of the absorbed 14C was excreted in the urine within 24 hr, only small amounts being found in urine excreted between 24 and 48 hr (< 2%) and between 48 and 72 hr (< 1%). About 1% of the dose was excreted in the faeces. Overall, the recovery of 14C was 77-88%. Less than 2% of the dose was found in the carcasses of rats 72 hours after dosing.

Details on distribution in tissues:

Levels of radioactivity in all the organs examined were lower in the animals killed 24 hr after administration of the test compound. Recovery of 14C in the skin and subcutaneous fat of the application site and surrounding area accounted for 3.7% of the dose immediately after the removal of the dressings and this had declined to 1.2% 24hr after dosing. Radioactivity remaining in the carcasses of the rats accounted for < 4% of the administered dose.

Details on excretion:

Most of the absorbed 14C was excreted in the urine within 24 hr, only small amounts being found in urine excreted between 24 and 48 hr (< 2%) and between 48 and 72 hr (< 1%). About 1% of the dose was excreted in the faeces.

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Hippuric acid was the major metabolite of the topically applied compound, accounting for c. 95% of urinary 14C. Also present were much smaller amounts of benzoyl glucuronide, benzoic acid and benzylmercapturic acid, each accounting for c. 1-2% of urinary radioactivity.
The proportions of the administered dose excreted as hippuric, benzoic and benzylmercapturic acids were not significantly influenced by dose size.

Any other information on results incl. tables

No additional information

Applicant's summary and conclusion

Conclusions:

The data presented provides information on the effects of various factors on the absorption and disposition of topically applied benzyl acetate in the rat.

Executive summary:

Methylene-¹⁴CBenzyl acetate was applied over an area of 6.25, 12 or 18 cm ² to the shaved backs of male Fischer 344 rats under an occlusive dressing at dose levels of 100, 250 and 500 mg/kg. The compound was administered either as the neat substance or as a 50% (v/v) solution in ethanol. After 6 hr the dressing was removed, the shaven area was washed with ethanol and the dressing and washings were counted for ¹⁴C. Urine and faeces were collected for 72 hr from the start of treatment and urinary metabolites were assayed by radio-TLC and HPLC. Following administration of the neat compound, a significant proportion of the dose was recovered from the application site (28-48%) and a similar proportion (28-46%) was absorbed and excreted in the 0-24-hr urine. Excretion of ¹⁴C in the urine over 0-24 hr accounted for c. 95% of absorbed ¹⁴C in all cases, and total recovery of radioactivity was 79-84% with <2% of the dose present in the carcass at the end of the experiments. The extent of absorption of benzyl acetate per unit area of skin, as assessed by the recovery of its metabolites in urine, rose with increasing concentration (mg/cm 2) of the test compound on the skin. The absorption of topically applied benzyl acetate was essentially the same when the dose was administered in a 50% ethanolic solution. In all cases, the major urinary metabolite was hippuric acid (c. 95% of urinary ~4C), together with much smaller amounts of benzoyl glucuronide, benzoic acid and benzylmercapturic acid. The distribution of 14C in the tissues was examined 6 and 24 hr after the topical application of 5 mg [methylene-14C]benzyl acetate/kg as a 1% (v/v) solution in ethanol to rats. Radioactivity in all carcasses was <4% of the administered dose and levels in all the organs examined were lower at 24 than at 6 hr.