Isopropyl acetate

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vivo

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For read across justification see the attachment in the read across object attached to chapter 7.4.1 (skin sensitisation).

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This experiment was specifically carried out to quantify the irritancy of the similar acetate ester ethyl acetate to assess its potential in transdermal drug delivery patches. The work is well reported and carried out to a protocol closely matching OECD 404. The ethyl acetate was not in direct contact with the skin of the test animals (separated by a 50um membrane) but in contrast exposure time was significantly longer than usual

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Deviations:

yes

Remarks:

, test substance not placed in direct contact (50um semi-permeable membrane separated test solvent from skin) but occlusion should not make this a material difference. Exposure time 24 hours.

Principles of method if other than guideline:

Evaluation of cutaneous side effects of transdermal patches delivering the drug levonorgestrel and ethyl acetate as a potential skin penetration enhancer. Test not performed according to OECD protocol but similar methodology used.

GLP compliance:

not specified

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

Rabbits were individually identified on the right ear using permanent ink marker.

TEST ANIMALS
- Source: Elkhorn Rabbitry (Watsonville, CA, USA).
- Weight at study initiation: 2-3 kg
- Housing: individually
- Diet: Purina rabbit chow ad libitum
- Water: uv purified drinking  water ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature: 22±2°C
- Humidity: 40-50%
- Photoperiod: 12 hour light/12hour dark  cycle

Type of coverage:

other: un-occlusive

Preparation of test site:

shaved

Vehicle:

unchanged (no vehicle)

Controls:

not specified

Duration of treatment / exposure:

3-7 patches were placed on each rabbit on new sites over the course of the experiment. Each patch remained in contact with the rabbits skin for 24 hours.

Observation period:

7 days

Number of animals:

4

Details on study design:

TEST SITE
- Area of exposure: dorsal area
- Type of wrap if used: non-occlusive Keri-towels secured with cloth surgical tape. Test cells were held in place for 24 hours after which another cell was placed in a different place for a further 24 hours.  Collars were used on the rabbits. 

SCORING SYSTEM: Each test site was subsequently assessed using the Draize scoring method (0 to 4) for erythema and odema at 0, 24, 48 hours and 7 days.  The irritation index was calculated (average sum of ethythema and odema across all 4 animals used) Individual scores are not tabulated but results are presented graphically with an indication of variability for ratings or erythema and odema. 

OTHER: Microscopic examinations were performed on skin tissues fixed in neutral buffered 10% formalin. Samples were routinely processed, embedded in paraffin, sectioned at 5 um, and stained with haematoxylin and eosin. Microslides were examined by light microscopy and the results tabulated.

Irritation parameter:

primary dermal irritation index (PDII)

Basis:

mean

Time point:

other: 24 h

Score:

1.7

Max. score:

8

Reversibility:

not fully reversible within: 7 days

Remarks on result:

other: tested using membrane polymer formulation 1

Irritation parameter:

primary dermal irritation index (PDII)

Basis:

mean

Time point:

other: calculated from 24, 48, 72 hour observations

Score:

1.3

Max. score:

8

Reversibility:

fully reversible within: 7 days

Remarks on result:

other: tested using membrane polymer formulation 2

Irritant / corrosive response data:

Formulation using 100% ethyl acetate as a penetration enhancing solvent produced mild erythema and no oedema, hence its scores are expressed only as a primary irritation index.

Two formulations were tested with differing membrane composition but both based on 100% ethyl acetate.

Formulation 1 (membrane 1)

	24 hours	48 hours	72 hours	7 days
Erythema	1.6	1.3	1.1	0.7
Odema	0.7	0.2	0.3	0.2
PII	2.3	1.5	1.4	0.9

Formulation 2 (membrane 2)

	24 hours	48 hours	72 hours	7 days
PII	1.5	1.3	1.0	0

Maximum Primary irritation index (PII) possible is 8.

Note that the control using water only produced slight irritation, indicating some contribution to overall irritancy from the test membranes.

Interpretation of results:

other: unreliable

Remarks:

Criteria used for interpretation of results: EU

Conclusions:

There are no known reports of levonorgestrel causing irritancy.  Some residual irritancy may have been caused by adhesive remaining on the skin following test cell removal.  There was also evidence for some contribution to mild irritancy from the membranes themselves. The results indicated that using EtAc-EtOH or neat EtAc in a transdermal delivery device is mildly to moderately irritating to rabbits.

Histological examination showed increased cellularity in the papillary and reticular dermis mile hyperkeratosis and scale crust formation.  The histological changes were reversible and consistent with a very mild subacute irritation as suggested by the visual assessment.  The conclusion was that use of ethyl acetate in a transdermal delivery device is mildly to moderately irritating to rabbits and would be expected to be non to mildly irritating to humans.

This study is not ideal but is deemed sufficiently reliable to characterise the skin irritancy properties of ethyl acetate.

Executive summary:

A study to examine ethyl acetate as a permeation enhancer solvent for transdermal drug delivery reported mild to moderate irritation to rabbit skin following application of a transdermal drug delivery device containing the drug levonorgestrel and neat ethyl acetate. Control devices containing only water were also found to be mildly irritating. Some residual irritancy may have been caused by adhesive remaining on the skin following test cell removal or the semi-permeable membrane used in the device. Whilst the solvent was not in direct contact with the skin (separated by the 50um membrane), the duration of exposure was significantly longer than required for a guideline study. This study is deemed sufficiently reliable to characterise ethyl acetate as not significantly irritating to the skin.

Cross-reference 2

Reason / purpose for cross-reference:

read-across source

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Basic data given comparable to guideline study (deviations: occlusive cover); was not conducted under GLP but has sufficient data for interpretation of results.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

Deviations:

not specified

GLP compliance:

no

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Diet: commercial available diet, ad libitum
- Water: municipal water, ad libitum

Type of coverage:

occlusive

Preparation of test site:

shaved

Vehicle:

unchanged (no vehicle)

Controls:

no

Amount / concentration applied:

TEST MATERIAL
- Amount applied: 0.5 ml

Duration of treatment / exposure:

4-hour contact

Observation period:

up to 10 days after 4 hour contact period

Number of animals:

6 (3 males and 3 females)

Details on study design:

READING TIMES: 1 hour, 24 hour, and 2, 3, 7 and 10 days after 4 hour contact period.

SCORING SYSTEM: Method of Draize

Irritation parameter:

erythema score

Basis:

mean

Time point:

other: 24, 48, and 72 h

Score:

0

Max. score:

4

Irritation parameter:

edema score

Basis:

mean

Time point:

other: 24, 48, and 72 h

Score:

0

Max. score:

4

Other effects:

One animal was found dead at 10 days from unknown causes, but most probably not treatment-related.

Interpretation of results:

not irritating

Remarks:

Migrated information Criteria used for interpretation of results: other: CLP regulation

Conclusions:

Under the conditions of this study, the substance N-Butyl Acetate was not irritating to the skin according to the criteria of the Regulation (EC) No. 1272/2008.

Executive summary:

A 4 -hour occlusive treatment of 6 rabbits with 0.5 mL of the the substance n-butyl acetate, which is structurally similar to isopropyl acetate, in a study similar to OECD TG 404 did not induce any erythema nor edema, therefore the test item does not reveal any irritating potential under the conditions tested. Such a result would be expected with isopropyl acetate.

Cross-reference 3

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

See attached justification below.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Remarks on result:

no indication of skin sensitisation

Materials and methods

Test material

Test material information

Constituent 1

Reference substance name:

Isopropyl acetate

EC Number:

203-561-1

EC Name:

Isopropyl acetate

Cas Number:

108-21-4

Molecular formula:

C5H10O2

IUPAC Name:

isopropyl acetate

Details on test material:

- Name of test material (as cited in study report): isopropyl acetate

Results and discussion

In vivo

Results

Remarks on result:

no indication of irritation

Irritant / corrosive response data:

Based on a weight of evidence approach using source substances, irritation is not sufficient to trigger requirement for classification.