Methyl salicylate

Specific investigations: other studies

Administrative data

Endpoint:

phototoxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well-conducted scientific study to GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

no guideline required

Principles of method if other than guideline:

Study of potential for photoxicity and photoallergy by dermal route in guinea pigs by method of Unkovic (1983).

GLP compliance:

yes (incl. QA statement)

Type of method:

in vivo

Test material

Test material information

Constituent 1

Reference substance name:

Methyl salicylate

EC Number:

204-317-7

EC Name:

Methyl salicylate

Cas Number:

119-36-8

Molecular formula:

C8H8O3

IUPAC Name:

methyl salicylate

Test animals

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, France
- Age at study initiation: 1-2 months
- Weight at study initiation: 402 +/- 26 g
- Fasting period before study: not applicable
- Housing: individually in polycarbonate cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 2
- Humidity (%): 30-70
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12:12

IN-LIFE DATES: Main study: From: 5 June 2003 to 17 july 2003

Administration / exposure

Route of administration:

dermal

Vehicle:

other: diethyl phthalate

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water): solubility
- Concentration in vehicle: 50%
- Lot/batch no. (if required): 12414LS-020 (Aldrich)

Duration of treatment / exposure:

Phototoxicity: 1 exposure (24 hours)
Photoallergy: 6 induction applications, 1 challenge application

Frequency of treatment:

Photoallergy: 6 applications over 8 days

Post exposure period:

Photoallergy: 20 days between induction & challenge

Doses / concentrations

Remarks:

Doses / Concentrations:
50%
Basis:
nominal conc.

No. of animals per sex per dose:

5 or 10

Control animals:

yes, concurrent vehicle

yes, sham-exposed

yes, historical

Examinations

Positive control:

8-Methylpsoralen, Phenothiazine

Results and discussion

Details on results:

Phototoxicity: In group 3 (MeS plus irradiation), discrete erythema (grade 1) was noted in 3/10 animals at 1 and 4 hours, but this did not persist on day 2. Questionable erythema (grade 0.5) was observed in a few animals, but was within the range of that shown in group 4 (irradiated vehicle controls). MeS was considered not phototoxic.
Photoallergy: Following challenge on day 29, questionable or discrete erythema was observed in almost all animals of groups 1, 3 and 4 at the 1 and 4 hour readings. These persisted in a few animals at the 24 hour reading. These slight and transient reactions, similar in controls and treated animals, remained within the range of a local reaction at an infra-erythematogenic irradiate dose and were not attributed to a photoallergenic response of the test item. MeS was considered not to be photoallergenic.

Any other information on results incl. tables

The concentration of 50% MeS in DEP was decided following the results of a preliminary study.

No deaths or clinical signs considered treatment-related were observed. Bodyweight gains were similar to controls.

In group 3 (MeS plus irradiation), discrete erythema (grade 1) was noted in 3/10 animals at 1 and 4 hours, but this did not persist on day 2. Questionable erythema (grade 0.5) was observed in a few animals, but was within the range of that shown in group 4 (irradiated vehicle controls). MeS was considered not phototoxic.

Following challenge on day 29, questionable or discrete erythema was observed in almost all animals of groups 1, 3 and 4 at the 1 and 4 hour readings. These persisted in a few animals at the 24 hour reading. These slight and transient reactions, similar in controls and treated animals, remained within the range of a local reaction at an infra-erythematogenic irradiate dose and were not attributed to a photoallergenic response of the test item. MeS was considered not to be photoallergenic.

Applicant's summary and conclusion

Conclusions:

MeS is not phototoxic or photoallergenic according to this test method.

Executive summary:

A study was carried out using the method of Unkovic (1983) to evaluate the potential of MeS to induce phototoxicity or photoallergenicity in guinea pigs. The study consisted of three phases: a single treatment by cutaneous application of MeS with ultra-violet irradiation to assess phototoxic potential, an induction phase performed by repeated cutaneous applications of MeSe with ultra-violet irradiation and a challenge phase performed by cutaneous application of MeS with ultra-violet irradiation to assess photoallergenic potential.

25 male Dunkin-Hartley guinea-pigs were allocated to four groups.

Group 1: 5 animals irradiated without MeS treatment

Group 2: 5 animals treated with MeS without irradiation

Group3: 10animals treated with MeS followed by irradiation

Group 4: 5 animals treted with vehicle (DEP) only

On the day before the first treatment, the intrescapular area of the animals was clipped and shaved. Thereafter,the same area was shaved again whenever necessary.

The phototoxicity of MeS was determined on days 1 and 2. On day 1, a dose-volume of 0.1 mL of MeS at 50% w/w in diethyl phthalate (DEP) was applied to the interscapular region of the anials of groups 2 and 3, on an area of approximately 9 cm2. a gentle massage was given to facilitate penetration of the test item into the epidermis. Animals of group 4 were treated with 0.1 ml of DEP vehicle under the same experimental conditions. Animals of group 1 received no treatment.

Approximately 30 minutes after treatment, the animals of groups 1, 3 and 4 were irradiated with an infra-erythematogenic dose (erythema score =< 0.5) of UVA (approximately 9 joules/cm2) and UVB (approximately 0.1 joules/cm2). The non-irradiated part of the back and flanks were protected from the UV rays.

Cutaneous reactions were scored before and 1, 4 and 24 hours after the single application and/or irradiation.

For photoallergy, the test was performed in three pahses (induction, rest period and challenge application0.

The treatment performed on day 1 for the determination of phototoxic potential was considered the first treatment of the induction period. Five more applications were performed, from day 2 to day 8, following the same procedure as on day 1. Cutaneous reactions were scored approximately 24 hours after each application and/or irradiation. After the 6^thapplication, the animals were free of any treatment for 20 days.

On day 28, the posterior right and left flanks of all animals were clipped and shaved. On day 29, a dose-volume of 0.1 mL of MeS at 50% in DEP was applied to two areas of 4 cm2 of the distal part of the back (ontreated during induction) of the animals of groups 2 and 3. Animals of group 4 were treated with 0.1 ml of DEP vehicle under the same experimental conditions. Animals of group 1 received no treatment.

Approximately 30 minutes after treatment, the animals of groups 1, 3 and 4 were irradiated, the left flank with UVb only, the right flank with UVA only. Doses and procedures were otherwise as for the induction phase.

Cutaneous reactions were scored before and 1, 4 and 24 hours after the challenge application and/or irradiation.

Scoring was according to the following scale:

0         No erythema

0.5       Questionable erythema (infra-erythematogenic dose)

1         Discrete and patchy erythema

2         Moderate and confluent erythema

3         Intense erythema

Animals were examined for any other lesions, morbidity, mortality, clinical signs and bodyweight change.

Treated and irradiated animals are considered to show positive phototoxic reactions if the cutaneous reactions recorded after the first application are clearly different from those of controls.

Treated and irradiated animals are considered to show positive photoallergic reactions if the cutaneous reactions recorded after the challenge application are clearly different from those of controls.

The test result is considered doubtful if only one or two animals show positive reactions.

The concentration of 50% MeS in DEP was decided following the results of a preliminary study.

No deaths or clinical signs considered treatment-related were observed. Bodyweight gains were similar to controls.

In group 3 (MeS plus irradiation), discrete erythema (grade 1) was noted in 3/10 animals at 1 and 4 hours, but this did not persist on day 2. Questionable erythema (grade 0.5) was observed in a few animals, but was within the range of that shown in group 4 (irradiated vehicle controls). MeS was considered not phototoxic.

Following challenge on day 29, questionable or discrete erythema was observed in almost all animals of groups 1, 3 and 4 at the 1 and 4 hour readings. These persisted in a few animals at the 24 hour reading. These slight and transient reactions, similar in controls and treated animals, remained within the range of a local reaction at an infra-erythematogenic irradiate dose and were not attributed to a photoallergenic response of the test item. MeS was considered not to be photoallergenic.