Dapsone

Endpoint summary

Description of key information

Based on available data median lethal dose through oral and dermal route for dapsone is >250 and >2000 mg/kg bw respectively.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: based on the requirements of Commission Directive 91/507/FEC, Pharmaceutical Affairs Bureau (Ministry of Health and Welfare) Notifications No.24 and No.88 and US FDA guidance on acute toxicity testing for pharmaceuticals.

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Sex:

female

Details on test animals or test system and environmental conditions:

Nulliparous, non-pregnant female New Zealand White rabbits of the Crl: NZW/Kbl.BR strain were obtained from Charles River UK Ltd, Margate, Kent on 6 July 1999. The animals were examined and weighed on the day of arrival. The rabbits were in a body weight range of 2.048 to 2.893 kg on Day --L Based on information from the supplier the rabbits were approximately twelve to fourteen weeks old on Day 1.
Rabbits were housed individually in floor-pens throughout the acclimatization and experimental phases of the study. Each pen had a minimum floor area of 0.6 m2. The partitions between pens were constructed of slotted laminate board 1.0 m high. The floor pens had solid floors. Wood chips were provided as floor litter. Each batch of wood chips was analysed for specific contaminants and the data are kept on file in the Covance Archive.
SQC TRB Rabbit Diet 9603 (pelleted) from Harlan Teklad, Bicester was freely available to the animals at all times. Each batch of diet is analysed for specific constituents and contaminants by the manufacturer.
Mains water was provided, ad libitum, from water bottles attached to the pen walls. The potable water supply is periodically analysed for specific contaminants. No contaminants were present in diet, bedding or water at levels that might have interfered with achieving the objective of the study.
The holding room was designed to permit at least 10 air changes per hour and to maintain temperatures of 16 to 22°C. Humidity was not actively controlled but was expected to remain within the range 40 to 80% RH. Recordings of maximum and minimum temperature and humidity were generally made twice daily except on some Saturdays, Sundays or public holidays during the study when only a single record was made without affecting the study integrity. On no occasion during the study did the temperature or humidity values fall outside the expected ranges. The room was illuminated by fluorescent strip-lights for twelve hours daily.

Route of administration:

oral: gavage

Vehicle:

methylcellulose

Remarks:

1% m/v aqueous methyl cellulose

Details on oral exposure:

Individual dose volumes (mL) were calculated from the body weights of the rabbits on the morning of dosing and the selected dose volume, 5 mL/kg. Each rabbit was dosed by passing a catheter along the oesophagus and instilling the test article into the gastric lumen. Plastic syringes and catheters were used.
Dose levels were expressed gravimetrically in terms of test article received (without regard to purity or active content). The test articles were dispersed, separately or in combination, in 1% m/v aqueous methyl cellulose. The formulated concentrations were calculated from the selected dose level and dose volume. All formulations were used on the day of preparation.

No procedures to limit particle size of test article in suspension, to sterilise the test formulations or to measure pH, osmolarity or other physico-chemical characteristic of the test formulations were undertaken. No analyses of the homogeneity, stability or achieved concentration of the test article in administered formulations were undertaken.

Doses:

Dapsone-250mg/kg
Chlorproguanil-200 mg/kg
Dapsone-125 mg/kg plus Chlorpruguanil- 100 mg/kg
Dapsone-250 mg/kg plus Chlorpruguanil - 200 mg/kg

No. of animals per sex per dose:

6 females/dose

Control animals:

no

Sex:

female

Dose descriptor:

LD50

Effect level:

> 250 mg/kg bw

Based on:

test mat.

Mortality:

No deaths were seen during the study.

Clinical signs:

other: No effects were seen

Gross pathology:

The mean liver weight showed a slight increase but a comparison of individual weights and organ/body weight ratios indicate that the mean increase is largely· attributable to one rabbit (no 12) which was the heaviest animal on study and this increase can not be directly attributed to a toxic effect of the test article. For the remaining organ weights, values among the treated rabbits were similar to those of the controls. Necropsy revealed a few red or dark foci on the lungs of three rabbits. These were considered likely to be agonal changes rather than treatment related effects.

Other findings:

A single elevated Heinz body count (animal no 7) resulted in a higher group mean percentage in Group 2. 'Methaemoglobin levels were slightly increased for four animals (0.1 to 0.6%) compared with zero values for all control samples. No other haematology parameters measured on Day 2 showed any notable changes.
Two animals (nos 8 & 10) had elevated Heinz body counts on Day 13 resulting in an increased group mean value. Methaemoglobin levels were slightly increased for two animals (0.2 to 0.4%) compared with a single value of 0.1% in the control samples. None of the other haematology parameters showed any marked differences from control values.
Comparison of the results obtained for animals treated with Dapsone with those from the control group revealed no notable differences in any of the measured clinical chemistry parameters

Interpretation of results:

Category 3 based on GHS criteria

Conclusions:

An acute oral median lethal dose (LD50) of Dapsone is > 250 mg/kg bw.

Executive summary:

The study was designed to investigate possible interactions following single oral administration of the two test articles, Chlorproguanil and Dapsone, in combination. The doses of the combined formulation included the MTD of Chlorproguanil (determined in CLE study number 1552/25) and a clinically relevant dose of Dapsone [Chlorproguanil:Dapsone in ratio 1:1.25]. A second, lower dose combination, group was included to provide data on a possible dose related trend. The study also included a single administration of each test article individually to investigate possible synergistic effects and to provide data for comparison with the dose combination groups.

The oral route of administration was used in this study because it is the likely human therapeutic route. Guidance on requirements for new drug registration issued by EU, MOHW and US FDA (1,2,3) requires single dose toxicity studies to be completed (including one non-rodent species for Japan and US). In addition, the expected metabolism of chlorproguanil in the rabbit was an important selection criterion. In humans, chlorproguanil is metabolised to the active metabolite, chlorcycloguaniL There is evidence that this pathway is absent or limited in rodents but that it does occur in rabbits. Hence the rabbit was the chosen test model for this study. Groups of six female rabbits were given a single oral dose of the vehicle control, one of the test articles or one of two doses of the combined formulation.

Administration of the low dose combined treatment resulted in no clearly adverse reactions although some changes suggesting a limited hepatic response were seen.

Administration of the high dose combination treatment resulted in a marked initial loss of appetite and weight loss that was similar to that observed following dosing with the equivalent dose of Chlorproguanil alone. Anogenital soiling, also apparent following dosing with Chlorproguanil, was noted shortly after dosing. However the combination treatment did not result in the death of any animals.

Increases in methaemoglobin concentration and erythrocytes with Heinz bodies, following administration of Dapsone, were more marked in the high dose combination group than in the group dosed with the equivalent dose of Dapsone alone. No such changes were seen in the low dose combination group.

Generally there were no responses seen in either of the two combination groups that indicated any enhancement of effects due to interaction between the two test articles. However there was some indication that the joint administration of the high dose may have slightly increased the normal effects of Dapsone alone on methaemoglobin levels and Heinz body production. No evidence for a clear enhancement of changes due to a synergistic reaction was apparent. There were also no findings that were unique to the combined treatment groups compared with the reactions seen following administration of either Dapsone or Chlorproguanil alone.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

> 250 mg/kg bw

Quality of whole database:

klimisch score 1

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Data waiving:

other justification

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPP 81-2 (Acute Dermal Toxicity)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Test type:

fixed dose procedure

Limit test:

yes

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Type of coverage:

occlusive

Details on dermal exposure:

TEST SITE
- Area of exposure: back of the animal (shaved)
- Type of wrap if used: polyethylene plastic

REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes
- Time after start of exposure: 24 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 2g/kg bw
- Constant volume or concentration used: yes/no no
- For solids, paste formed: yes, 1% in a gel paste

Duration of exposure:

24 hours

Doses:

2000 mg/kg

No. of animals per sex per dose:

Each 5 males and 5 females

Control animals:

not required

Details on study design:

Ten rabbits (5 per gender) were used. The back of each animal was haved. Half the animals received epidermal abrasions on the shaved area. The test article (1% dapsone gel) was applied to the back of each animal at a dose of 2g/kg and covered with polyethylene plastic. The rabbits were fitted with collars and the test article was left in place for 24 hours. The test sites were then wiped clean and the rabbits were monitored for 14 days for signs of illness, mortality,, and dermal reactions (erythema and edema) at the site of application. Body weights were recorded at the time of dosing and after 14 days.

Preliminary study:

Very slightly (barely perceptible) erythema was observed for the first 7 to 12 days after treatment; this may have been due to shaving, occlusion, taping, etc. No edema was observed. No effects on body weight, survival, clinical signs, or gross necropsy were observed.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

act. ingr.

Mortality:

None

Clinical signs:

other: Very slightly (barely perceptible) erythema was observed for the first 7 to 12 days after treatment; this may have been due to shaving, occlusion, taping, etc. No edema was observed.

Gross pathology:

No effect

Other findings:

No effects on body weights

Interpretation of results:

GHS criteria not met

Conclusions:

The median lethal dose by dermal route in NZW rabbits (LD50) was > 2000 mg/kg.

Executive summary:

An acute dermal toxicity study is available in the Norman A. See, Pharmacology review (2005). The study was conducted in compliance with gool laboratory practice in 1997. Ten New Zealand white rabbits (5 per gender) were used. The back of each animal was shaved. Half the animals recieved epidermal abrasions on the shaved area. The test article (1% dapsone gel) was applied to back of each animal at a dose of 2g/kg and covered with polyethylene plastic. The rabbits were fitted with collars and the test article left in place for 24 hours. The test sites were then wiped clean and the rabbits were monitored for 14 days for signs of illness, mortality and dermal reactions (erythema and edema) at the site of application. Body weights were recorded at the time of dosing and after 14 days. 

Very slight erythma was observed for the first 7 to 12 days after treatment; this may have been due to shacing, occlusion, taping, etc. No edema was observed. No effects on body weight, survival, clinical signs or gross necropsy were observed. 

Under the conditions of this study, the test article did not appread to induce toxicity. 

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

> 2 000 mg/kg bw

Quality of whole database:

klimisch score 1

Additional information

Acute oral toxicity:
Under test conditions in rabbit, an acute oral median lethal dose (LD50) of Dapsone is > 250 mg/kg bw.

In a supporting study from published literature LD0 value is 600 mg/kg bw with no toxic effect detectable, and LDLo range is 700 to 910 mg/kg with self-mutilations observed which indicates a low toxicity. Also a variety of acute oral toxicity studies with Dapsone as a pharmaceutical have been conducted in humans and the range of TDlows when the substance is orally applied is 18 - 37.5 mg/kg bw which confirms a low toxicty as well in Human.

Acute Dermal Toxicity:

Based on the study from published literature, the median lethal dose by dermal route in NZW rabbits (LD50) was > 2000 mg/kg.

Acute dermal toxicity:

Justification for classification or non-classification

The substance is classified for acute oral toxicity (Cat 3) with an LD50 >250 mg/kg bw. The substance is also classified for Specific Target Organ Toxicity after single exposure Category 2 for effects on blood due to methemoglobin formation. There is no classification required for acute toxicity on the dermal route.