2,4-diethyl-9H-thioxanthen-9-one

Eye irritation

Administrative data

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

09 June 1998 to 15 June 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 405 (Acute Eye Irritation / Corrosion)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.5 (Acute Toxicity: Eye Irritation / Corrosion)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2-isopropyl-9H-thioxanthen-9-one

EC Number:

226-827-9

EC Name:

2-isopropyl-9H-thioxanthen-9-one

Cas Number:

5495-84-1

Molecular formula:

C16H14OS

IUPAC Name:

2-(propan-2-yl)-9H-thioxanthen-9-one

Test material form:

solid: particulate/powder

Details on test material:

- Appearance: yellow powder

Test animals / tissue source

Species:

rabbit

Strain:

New Zealand White

Details on test animals or tissues and environmental conditions:

TEST ANIMALS
- Age at study initiation: 11 to 14 weeks old
- Weight at study initiation: 2.25 to 2.51 kg
- Housing: Rabbits were housed in floor-pens, each accommodating one animal throughout the acclimatisation and experimental phases of the study. Each pen had a minimum floor area of 0.6 square metres. The partitions between pens were constructed of slotted laminate board 1.0 m high. Wood chips were provided as floor litter. Each batch of wood chips was analysed for specific contaminants.
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 10 to 13 days
- Both eyes of each rabbit were examined for indications of corneal, iridial or conjunctival damage or irritation. After initial visual examination, one drop of 2 % aqueous fluorescein solution was instilled into both lower conjunctival sacs, allowed to disperse for thirty seconds and removed from the eyes by irrigation with approximately 10 mL water for irrigation jetted gently from a syringe. The corneal surface was illuminated with an ultraviolet source and inspected for areas of absorption of the fluorescing dye that would indicate epithelial damage. Only rabbits with eyes free from damage or irritation were accepted onto study.

ENVIRONMENTAL CONDITIONS
- Temperature: 16 to 22 °C
- Humidity: 40 to 80 % (expected range)
- Air changes: 10 air changes per hour
- Photoperiod: The room was illuminated by fluorescent strip-lights for twelve hours daily.

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent no treatment

Amount / concentration applied:

TEST MATERIAL
- Amount applied: Approximately 55 mg (the weight equivalent to 0.1 mL)

Duration of treatment / exposure:

After instillation the eyelids were held closed for a few seconds to prevent loss of the dose.

Observation period (in vivo):

3 days

Number of animals or in vitro replicates:

3 animals

Details on study design:

EXPERIMENTAL PROCEDURE
- Before the first animal could be dosed the pH of the test material was checked. A 25 % m/v dispersion in purified water had a pH of 5.0. Since this was within the acceptable range of pH 2.0 to 11.5, the study continued.
- One dose consisting of approximately 55 mg (the weight equivalent to 0.1 mL) of powdered test material, dispensed from a spatula, was instilled into the left conjunctival sac of a single New Zealand White rabbit (the "sentinel"). The lower eyelid was gently prised away from the eyeball to create a receptacle for the dose. After instillation the eyelids were held closed for a few seconds to prevent loss of the dose. The right eye remained untreated and served as a control to the treated eye. The day of dosing was designated as Day 1. The condition of the treated eye of the sentinel was assessed for a period of at least three days to ensure the test material did not cause ocular damage.
- Subsequently, approximately 55 mg of test article, as supplied, was similarly instilled into the left conjunctival sac of each of two further rabbits.


EXPERIMENTAL OBSERVATIONS
- Clinical signs: A detailed account of any clinical signs of ill health was maintained.
- Body weights: Each rabbit was weighed on the day before dosing (Day -1).
- Ocular response: The "initial sting" response was assessed and recorded immediately after instillation of the test material. The response was graded according to the following scheme:
No response = 0 = None
A few blinks only, normal within two minutes = 1 = Practically none
Rabbit blinks and attempts to open eye but reflex closes it = 2 = Slight
Rabbit keeps eye shut and puts pressure on it, may rub eye = 3 = Moderate
Rabbit holds eye tightly shut, may struggle or squeal = 4 = Marked

- Ocular changes were assessed and recorded immediately, half an hour, one and four hours after treatment on Day 1 and 24, 48 and 72 hours after dosing. Ocular changes were graded according to the following scheme:
- Cornea- degree of opacity
No ulceration or opacity = 0
Scattered or diffuse areas of opacity other than slight dulling of normal lustre, details of iris clearly visible = 1
Easily discernible translucent area, details of iris slightly obscured = 2
Nacreous area, no details of iris visible but size of pupil barely discernible = 3
Opaque cornea, iris not discernible through opacity = 4

- Cornea- area of corneal opacity
Total area of opacity amounts to < 25 % of corneal area = 1
Area of opacity amounts to 25 to < 50 % of corneal area = 2
Area of opacity amounts to 50 to < 75 % of corneal area = 3
Area of opacity amounts to 75 % or more of corneal area = 4

- Iris
No reaction = 0
Markedly deepened rugae, congestion, swelling, moderate circumcorneal hyperaemia or injection, any of these or any combination thereof: iris still reacting to light = 1
No iridial reflex to light, haemorrhage or gross destruction (any or all of these) = 2

- Conjunctivae - redness
Blood vessels normal = 0
Some blood vessels definitely hyperaemic (injected) = 1
Diffuse, crimson colour, individual vessels not easily discernible = 2
Diffuse beefy red appearance = 3
This refers to the most severe readting of palpebral and bulbar conjunctivae as compared to the right control eye.

- Conjunctivae - chemosis
No swelling = 0
Any swelling above normal = 1
Obvious swelling with partial eversion of lids = 2
Swelling with lids about half-closed = 3
Swelling with lids more than half-closed = 4
Assessment includes the nictitating membrane.

- Conjunctivae - discharge
No discharge = 0
Any discharge greater than normal, not including the small amount normally present in the inner canthus = 1
Discharge with moistening of eyelids and hairs just adjacent to the eye = 2
Discharge with moistening of eyelids and hair for a considerable area around the eye = 3

- The treated eyes were examined visually and, where appropriate, with the aid of a device to illuminate the eye.
- At examinations carried out 24 hours after treatment 2 % aqueous fluorescein solution was applied to the cornea and then washed out with water for irrigation or purified water. The corneal surface was then illuminated by an ultraviolet source and inspected for areas of epithelial disruption highlighted by absorption of the fluorescing dye.

TERMINAL PROCEDURES
- All rabbits were killed by intravenous injection of an overdose of sodium pentobarbitone, following confirmation that the condition of the treated eyes was normal on Day 4. No tissue preservation or histopathological assessment of tissues was undertaken.

Results and discussion

In vivo

Results

Results 1

Irritation parameter:

cornea opacity score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

4

Results 2

Irritation parameter:

iris score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

2

Results 3

Irritation parameter:

conjunctivae score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

3

Results 4

Irritation parameter:

chemosis score

Basis:

mean

Time point:

24/48/72 h

Score:

0

Max. score:

4

Other effects:

OCULAR RESPONSE
- Instillation of the test material caused no initial sting response.
- A single instillation of the test material caused some injection of the blood vessels of the conjunctivae in two rabbits on Day 1. A small amount of discharge was noted following treatment of one rabbit one half hour after dosing only. There were no other reactions to treatment and the absence of absorption of applied fluorescein dye showed that there was no damage to the epithelium. All reactions had resolved by Day 2.

CLINICAL SIGNS
- No observations were noted for any rabbits during the course of the study.
- One rabbit voided soft faeces on Day 2 but was normal by Day 3. This finding was not considered to be indicative of systemic toxicity or ill health.

Any other information on results incl. tables

Table 1: Group mean values for ocular reactions

Time of observation (h)	Ocular reaction
	Corneal opacity	Iris	Conjunctival redness	Chemosis
1	0.0	0.0	0.7	0.0
4	0.0	0.0	0.7	0.0
24	0.0	0.0	0.0	0.0
48	0.0	0.0	0.0	0.0
72	0.0	0.0	0.0	0.0
Mean of 24, 48 and 72 hour scores	0.0	0.0	0.0	0.0

 

Applicant's summary and conclusion

Interpretation of results:

other: Not classified in accordance with EU criteria

Conclusions:

Under the conditions of the study, the test material 2-Isopropylthioxanthone (CAS 5495-84-1, EC 226-827-9) has been determined to be not irritating.

Executive summary:

A study was conducted to investigate the potential of the test material 2-Isopropylthioxanthone (CAS 5495-84-1, EC 226-827-9) to cause eye irritation in accordance with the standardised guidelines OECD 405 and EU Test Method B.5 under GLP conditions.

The test material (nominally 55 mg: weight equivalent to 0.1 mL) was instilled into one conjunctival sac of each of three New Zealand White rabbits on Day 1. Ocular reactions were assessed for up to three days after treatment.

Ocular instillation of the test material provoked no initial sting reaction.

A single instillation of the test material caused some injection of the blood vessels of the conjunctivae in two rabbits on Day 1. A small amount of discharge was noted following treatment of one rabbit one half hour after dosing only. There were no other reactions to treatment. All reactions had resolved by Day 2.

Under the conditions of the study, the test material 2-Isopropylthioxanthone (CAS 5495-84-1, EC 226-827-9) has been determined to be not irritating.