Nicotinamide

Endpoint summary

Description of key information

The test item was considered practically non-toxic following acute exposure via the oral, inhalation or dermal route. The key acute oral toxicity study was carried out in rats according to EU Method B.1 tris and OECD Guideline 423 (Acute Oral Toxicity - Acute Toxic Class Method). The acute oral LD50 was estimated to be > 2500 mg/kg bw. The NOAEL was determined to be 2000 mg/kg bw. Supporting studies in rat, mouse and rabbit confirmed that the test material is practically non-toxic following single oral administration. The key study on acute inhalation toxicity was carried out using Niacine. Niacine may be used in a read-across approach for Nicotinamide, as both compounds are convertible within the human body. The study was carried out according to OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class (ATC) Method). The LC50 for 4-hour exposure of Niacin obtained was greater than 3.8 mg/L air (chemically determined mean aerosol concentration), which was the highest achievable aerosol concentration. In the key dermal toxicity study in rats was carried out according to EU Method B.3 and OECD Guideline 402 (Acute Dermal Toxicity). In this limit test the LD50 for males/females was > 2000 mg/kg bw. In conclusion, the test item was considered practically non-toxic administered via the oral, inhalation or dermal route.

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

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EU Method B.1 tris (Acute Oral Toxicity - Acute Toxic Class Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

SafePharm Laboratories Ltd.

Test type:

acute toxic class method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 8 to 12 weeks old
- Weight at study initiation: males weighed 211 to 240g, females 223 to 236g
- Fasting period before study: Overnight fast immediately before dosing and for approximately three to four hours after dosing
- Housing: Housed in groups of three by sex in solid-floor polypropylene cages furnished with woodflakes
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: At least five days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25
- Humidity (%): 30 to 70
- Air changes (per hr): Approx. 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES
- From: 04 April 2000 To: 04 April 2000

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

MAXIMUM DOSE VOLUME APPLIED
- 10 mL/kg bw

All animals were dosed once only by gavage. The volume administered to each animal was calculated according to the fasted bodyweight at the time of dosing. Treatment of animals was sequential. Sufficient time was allowed between each sex to confirm the survival of the previously dosed animals.

Doses:

2000 mg/kg bw (male/female)

No. of animals per sex per dose:

3 animals per sex and dose

Control animals:

no

Details on study design:

- Duration of observation period following administration: The animals were observed for deaths or overt signs of toxicity 1/2, 1, 2 and 4 hours after dosing and subsequently once daily for fourteen days.
- Frequency of observations and weighing: Individual bodyweights were recorded prior to dosing and seven and fourteen days after treatment.
- Necropsy of survivors performed: Yes
- Other examinations performed: All animals were subjected to gross pathological examination. This consisted of an external examination and opening of the abdominal and thoracic cavities for examination of major organs. The appearance of any macroscopic abnormalities was recorded.

Statistics:

Not applicable.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 500 mg/kg bw

Based on:

test mat.

Sex:

male/female

Dose descriptor:

LD0

Effect level:

2 000 mg/kg bw

Based on:

test mat.

Mortality:

There were no deaths.

Clinical signs:

other: Hunched posture was noted in all animals during the day of dosing and one day after dosing. Lethargy was also noted in two females during this time.

Gross pathology:

No abnormalities were noted at necropsy.

Interpretation of results:

practically nontoxic

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The acute oral median lethal dose (LD50) of the test material in the Sprague-Dawley CD strain rat was estimated to be greater than 2500 mg/kg bw. The test item was considered practically non-toxic.

Executive summary:

A study was performed to assess the acute oral toxicity of the test material following a single oral administration to the Sprague-Dawley CD strain rat. The method followed EU Method B.1 tris and OECD Guideline 423 (Acute Oral Toxicity - Acute Toxic Class Method). Using all available information, 2000 mg/kg bw was selected as the starting dose. A group of three fasted males was treated with the starting dose. This was followed by a group of three fasted animals of the other sex at the same dose level. The test material was administered orally as a solution in distilled water. The animals were observed1, 2 and 4 hours after dosing and then once daily for fourteen days. Bodyweights were recorded on Day 0 (day of dosing) and on Days 7 and 14. At the end of the observation period all animals were killed by cervical dislocation and subjected to gross necropsy. There were no deaths. Hunched posture was noted in all animals during the day of dosing and one day after dosing. Lethargy was also noted in two females during this time. All animals showed expected gains in bodyweight over the study period. No abnormalities were noted at necropsy. The acute oral median lethal dose (LD50) of the test material, in the Sprague-Dawley CD strain rat, was estimated as being greater than 2500 mg/kg bw. The test item was considered practically non-toxic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 500 mg/kg bw

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study data on Nicotinic acid may be used in a read-across approach for Nicotinamide, as both compounds are convertible within the human body. Both compounds belong to vitamin B3 or vitamin PP. Nicotinamide is present primarily as NAD and NADP. NAD and NADP may be hydrolysed to form nicotinamide, which then may be absorbed either as such, or following further hydrolysis to nicotinic acid. Nicotinic acid is not directly converted to Nicotinamide in vivo, but both compounds can be converted to NAD and NADP. The conversion of nicotinic acid to nicotinamide occurs subsequent to its formation as a pyridine nucleotide; nicotinic acid reacts with 5-phosphoribosyl-1-pyrophosphate to form the nicotinic acid mononucleotide, which then condenses with ATP to form the nicotinic acid analogue of NAD, which is subsequently converted to NAD by a reaction with glutamine and ATP. In contrast, nicotinamide is converted to the pyridine nucleotide simply by reaction with phosphoribosyl-1-pyrophosphate. The cofactor NAD is converted to NADP by reaction with ATP. Nicotinamide can be formed from NAD via enzymatic cleavage to nicotinamide and adenosine diphosphate ribose.

Qualifier:

according to guideline

Guideline:

OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Harlan Laboratories Ltd.

Test type:

acute toxic class method

Limit test:

yes

Species:

rat

Strain:

other: RccHanTM:WIST(SPF)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation:
Males: 9 weeks (Groups 1 and 3), 10 weeks (Group 2)
Females: 9 weeks (Groups 1 and 3), 10 weeks (Group 2)
- Weight at study initiation:
Males: 271.4 to 309.0 g
Females: 174.8 to 198.2 g
The weight variation did not exceed ± 7 % of the mean weight of the corresponding sex.
- Fasting period before study: None
- Housing: Makrolon® type-IV cages with wire mesh tops and standard softwood bedding including paper enrichment
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: At least six days under optimal hygienic laboratory conditions. Only animals without any visible signs of illness were used for the study. A further observation of clinical signs was performed on the day of each exposure, before exposure start. The animals were accustomed to the restraining tubes for 30 minutes on the day of exposure.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 30 - 70%
- Air changes (per hr): 10 - 15 air changes per hour
- Photoperiod: 12 hour fluorescent light / 12 hour dark cycle

IN-LIFE DATES: From: 21-Dec-2011 To: 08-Feb-2012

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Flow-past, nose-only exposure system
- Method of holding animals in test chamber: Restraining tubes
- Rate of air: 1.0 L/min
- System of generating aerosols: A dust aerosol was generated from the test item using a CR3020 rotating brush aerosol generator connected to a micronizing jet mill. The aerosol generated was then discharged into the exposure chamber through a 63Ni charge neutralizer. The concentration of the test item in the inhalation chamber was controlled by regulating the flow of the test item to the inhalation tower.
- Method of particle size determination: The particle size distribution of the test aerosol was determined three times during each exposure using a Mercer 7 stage cascade impactor. The particle size distribution was measured by gravimetrically analyzing the test item deposited on each stage of the cascade impactor. Mass Median Aerodynamic Diameters (MMAD) and Geometric Standard Deviations (GSD) were calculated on the basis of the results from the impactor, using Microsoft Excel Software. The target range was 1 to 4 μm for the MMAD and between 1.5 and 3 for the GSD.
- Temperature, humidity, pressure in air chamber:
Relative Humidity / Temperature
The temperature and relative humidity of the test atmosphere was measured continuously during each exposure using a calibrated device. The results were recorded manually and are reported in 30 minute intervals from the start of exposure.
Oxygen Concentration
The oxygen concentration of the test atmosphere was measured continuously during each exposure using a calibrated device. The results were recorded manually and are reported at 30 minute intervals from the start of exposure. The oxygen concentration was maintained above 19 % during each exposure.
Airflow Rate
The actual airflow rate through the exposure chamber was recorded in approximately 30 minute intervals from the start of the inhalation exposure.

TEST ATMOSPHERE
- Brief description of analytical method used:
Determination of the Nominal Aerosol Concentration
The test item usage was measured by weighing the generator cylinders containing the test item before and after each exposure to determine the quantity of test item used. The weight used was then divided by the total air-flow volume to give the nominal concentration.
Gravimetric Determination of Aerosol Concentrations
Gravimetric determinations of aerosol concentration were performed eight times during exposure of group 1 and six times during exposure of groups 2 and 3. The samples were collected on a filter, Type HVLP loaded in a 47 mm in-line stainless steel filter sampling device. The filters were weighed before and immediately after sampling using a calibrated balance. The test aerosol concentration was calculated from the amount of test item present on the filter and the sample volume.
Chemical Determination of Aerosol Concentrations
Chemical determinations of aerosol concentration were performed eight times during exposure of group 1 and six times during exposure of groups 2 and 3 using the filters for gravimetric determinations.
The samples were collected on a HVLP filter loaded in a stainless steel filter device. The filters were transferred into appropriate labeled vials, forwarded at ambient conditions to the scientist responsible for formulation analysis and stored at room temperature until analysis. The samples were analyzed using a HPLC method supplied
- Samples taken from breathing zone: Yes

TEST ATMOSPHERE
The Mass Median Aerodynamic Diameters (MMAD) obtained from three gravimetric measurements of particle size distribution during the exposure for each group were similar (MMAD between 2.39 μm and 3.83 μm). This led to the conclusion that the particle size distribution of the generated aerosol was stable during the whole exposure period. The MMADs were midway through the target range of 1 to 4 μm, thus deposition of the particles can be
assumed to have occurred in both the upper and the lower respiratory tract. In addition, the Geometric Standard Deviations (GSD) were within the target range of 1.5 to 3, except for the first measurement for group 3 which was slightly above 3. In conclusion, the particle size distributions obtained were considered to be respirable to rats and appropriate for acute inhalation toxicity testing.

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration:
Group 1: The target concentration was chosen due to expected respiratory irritancy.
Group 2: The target concentration is the recommended concentration after exposure at 0.5 mg/L air.
Group 3: The target concentration of 2.5 mg/L air was the highest feasible aerosol concentration as determined in the technical trials.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

HPLC/UV

Duration of exposure:

4 h

Concentrations:

Nominal test concentrations:
Group 1: 0.5 mg/L air
Group 2: 1.0 mg/L air
Group 3: 2.5 mg/L air

No. of animals per sex per dose:

3 males and 3 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Each animal was examined three times during exposure, immediately and 1 h after exposure on test day 1 and once daily during the observation period. Observations were detailed and carefully recorded using explicitly defined scales as appropriate. Only grossly abnormal signs were detectable during exposure as the animals were restrained in the exposure tubes. The body weight of each animal was recorded on test days 1 (before exposure), 2, 4, 8 and 15 (before necropsy).
- Necropsy of survivors performed: Yes

Statistics:

No statistical analysis was performed.

Sex:

male/female

Dose descriptor:

LC0

Effect level:

3.8 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 3.8 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

All animals survived the scheduled observation period.

Clinical signs:

other: Group 1 (0.54 mg/L air): Tachypnea was observed in all animals during exposure period. After exposure end tachypnea and ruffled fur were recorded until test day 3. There were no clinical sings from test day 4 onwards. Group 2 (1.1 mg/L air): Tachypnea was

Body weight:

Group 1 (0.54 mg/L air):
From test day 1 to test day 2, slight body weight loss was noted in all males and two females. Stagnation of body weight was observed from test day 4 to 8 in the remaining female. Thereafter normal body weight development was recorded in all animals.
Group 2 (1.1 mg/L air):
From test day 1 to test day 2, slight body weight loss was noted in one male and two females. Stagnation of body weight was observed in the remaining two males during this period. Slight body weight loss from test day 2 to 4 was seen in the remaining female. Thereafter normal body weight development was recorded in all animals.
Group 3 (3.8 mg/L air):
From test day 1 to test day 2, slight body weight loss was noted in two males and all females. Further body weight loss was observed in one female until test day 4. Slight body weight loss was seen in the remaining male from test day 2 to 4. Thereafter normal body weight development was recorded in all animals.

Gross pathology:

No macroscopic findings at any group were present at necropsy.

Other findings:

None.

Interpretation of results:

practically nontoxic

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Treatment of RccHanTM:WIST(SPF) rats with Niacin at a concentration of 0.54, 1.1 or 3.8 mg/L air for 4 hours resulted in effects on body weight and clinical signs, such as tachypnea, ruffled fur and / or salivation. The observation on body weights exceeded the marginal body weight loss or stagnation of the body weight gain which is usually observed in acute inhalation studies. Therefore this was considered to be mainly an effect of the test item, especially due to the persistence until test day 4 or 8 in single animals. However, the restraining of the animals in the tubes during the nose only exposure procedure may have added to the observed effect. In conclusion, the LC50 for 4-hour exposure of Niacin obtained in this study was greater than 3.8 mg/L air (chemically determined mean aerosol concentration), which was the highest achievable aerosol concentration. There was no indication of relevant sex-related differences in toxicity of the test item.

Executive summary:

An acute inhalation toxicity study was carried out according to OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class (ATC) Method). Groups of male and female rats were treated with Niacin at a concentration of 0.54, 1.1 or 3.8 mg/L air for 4 hours. The LC50 for 4-hour exposure of Niacin obtained in this study was greater than 3.8 mg/L air (chemically determined mean aerosol concentration), which was the highest achievable aerosol concentration. There was no indication of relevant sex-related differences in effects of the test item. The test item was considered practically non toxic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

3 800 mg/m³ air

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

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

EU Method B.3 (Acute Toxicity (Dermal))

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rabbit

Strain:

other: White Russian (albino)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Males 14 - 16 months; Females 9 - 15 months
- Weight at study initiation: Males 2.38 - 2.95 kg; Females 2.48 - 2.93 kg
- Fasting period before study: 16 hours before treatment
- Housing: Stainless steel cages with grating floor, type ASTA, size: 48.5x40x36.5 cm (LxBxH), supplied by ASTA Pharma AG, 0-4800 Bielefeld, Germany
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: The animals were kept at least 5 days under test conditions before substance application after hair clipping. Veterinary supervision of the animals was done before start of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.0 - 22.5
- Humidity (%): 40 - 70 for a short period down to 35 %; this deviation was without any influence on the results of the study
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 6 a.m. to 6 p.m. artificial lighting, 6 p.m. - 6 a.m. natural light-dark-rhythm

IN-LIFE DATES:
- From: 14 Aug. 1990
- To: 29 Aug. 1990

Type of coverage:

occlusive

Vehicle:

water

Details on dermal exposure:

TEST SITE
- Area of exposure: Shorn skin between shoulder and sacral region
- % coverage: 100 %
- Type of wrap if used: Occlusive bandage

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

Duration of exposure:

24 hours

Doses:

Males 2000 mg/kg bw; Females 2000 mg/kg bw

No. of animals per sex per dose:

5 Males; 5 Females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: The animals were continuously observed for the first 4 to 6 hours after application and then once daily. The nature of the toxicity as well as the onset, the intensity, and the duration of the signs were recorded. Mortality was checked twice daily (a.m. and p.m.), on Saturdays, Sundays, on national and business holidays only once daily. The body weights were recorded at the beginning and also 7 and 14 days after application.
- Necropsy of survivors performed: A gross necropsy was performed on all animals. Macroscopical examination included external appearance, body orifices, body cavities (thoracic and abdominal), and their contents.

Statistics:

Not applicable.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Sex:

male/female

Dose descriptor:

LD0

Effect level:

2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality occurred.

Clinical signs:

other: The only sign of toxicity was a slight reddening of the application site detected immediately after removal of the patches. The finding was present in some animals up to the end of the observation period. Clinical symptoms are shown in table 1.

Gross pathology:

At necropsy no abnormal findings, except the a.m. slight reddening at the application site, were recorded.

Table 1: Male animal clinical symptoms

Dose	Symptoms	No. Animals
2000 mg/kg bw	Slight reddening of the application site	5/5

Table 2: Female animals clinical symptoms

Dose	Symptoms	No. Animals
2000 mg/kg bw	Slight reddening of the application site	5/5

Table 3: Male and female body weights

Dose (mg/kg bw)	Dermal Animal No.	Day 0	Day 7	Day 14
Male Animals		Body weights (kg)
2000	2203	2.44	2.45	2.45
	2215	2.56	2.56	2.56
	2205	2.38	2.34	2.34
	2217	2.47	2.47	2.47
	2263	2.95	2.89	2.89
Female Animals
2000	2286	2.48	2.5	2.5
	2294	2.49	2.47	2.47
	2288	2.86	2.84	2.89
	2290	2.54	2.55	2.51
	2238	2.93	2.94	2.96

Interpretation of results:

practically nontoxic

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Nicotinamide was tested for acute toxicity after single dermal application to rabbits. The LD50 values for male as well as female rabbits were above 2000 mg/kg bw (limit test).

Executive summary:

A study according to EU Method B.3 and OECD Guideline 402 (Acute Dermal Toxicity) was carried out. Nicotinamide was tested for acute toxicity after single dermal application to rabbits. The test substance, available as a white, crystalline powder, was moistened with water and placed on the shorn dorsal skin of 5 male and 5 female animals under occlusive conditions for 24 hours. The dose was 2000 mg/kg bw (limit concentration). The only sign of toxicity was a slight reddening of the application site detected immediately after removal of the patches. The finding was present in some animals up to the end of the observation period. Deaths did not occur. At necropsy no abnormal findings, except the slight reddening at the application site, were recorded. The LD 50 values for male as well as female rabbits were above 2000 mg/kg bw (limit test). Nicotinamide was considered practically non-toxic.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Additional information

Acute toxicity oral – key study

The key study assessed acute oral toxicity of the test material following a single oral administration to the Sprague-Dawley CD strain rat. The method followed EU Method B.1 tris and OECD Guideline 423 (Acute Oral Toxicity - Acute Toxic Class Method). Using all available information, 2000 mg/kg bw was selected as the starting dose. A group of three fasted males was treated with the starting dose. This was followed by a group of three fasted animals of the other sex at the same dose level. The test material was administered orally as a solution in distilled water. The animals were observed 1, 2 and 4 hours after dosing and then once daily for fourteen days. Bodyweights were recorded on Day 0 (day of dosing) and on Days 7 and 14. At the end of the observation period all animals were killed by cervical dislocation and subjected to gross necropsy. There were no deaths. Hunched posture was noted in all animals during the day of dosing and one day after dosing. Lethargy was also noted in two females during this time. All animals showed expected gains in bodyweight over the study period. No abnormalities were noted at necropsy. The acute oral median lethal dose (LD50) of the test material, in the Sprague-Dawley CD strain rat, was estimated as being greater than 2500 mg/kg bw. Nicotinamide was considered practically non-toxic.

Acute toxicity oral – supporting study 1

A study equivalent or similar to EU Method B.1 and OECD Guideline 401 (Acute Oral Toxicity) was carried out in young albino rats. Following single oral administration of test item the LD50 for male and female animals was determined to be 7100 mg/kg bw and 5500 mg/kg bw, respectively. Nicotinamide was considered practically non-toxic.

Acute toxicity oral – supporting study 2

A study similar or equivalent to EU Method B.1 and OECD Guideline 401 (Acute toxicity oral) was carried out. In a preliminary test fasted mice, rats and rabbits (2 male/2 female) were administered single oral doses of 500, 1000, 2500 and 5000 mg/kg bw. These groups were observed for a period of one week and the signs of toxicity and total deaths in each group noted. On the basis of the range-finding trials, the LD50 determination was performed using mice. In the main test fasted mice (Tyler's Original) (5 male/5 female) were given a single oral dose (gavage) of 2000, 2500, 3000, 3500, 4000 mg/kg bw and observed daily for 14 days. The LD0 obtained for males/females was 2000 mg/kg bw. The LD50 for males/females was 3100 mg/kg bw.Nicotinamide was considered practically non-toxic.

Acute toxicity oral – supporting study 3

A study according to EU Method B.1 and OECD Guideline 401 (Acute Oral Toxicity) was carried out in male and female rats. The highest dose administered that caused no mortality in males or females (LD50) was found to be 2400 mg/kg bw. The LD50 of nicotinic acid-amide for male and female rats was calculated to be 3530 mg/kg bw and 3540 mg/kg bw, respectively. The results do not suggest a difference in sensitivity to the test substance between male and female rats. Nicotinamide was considered practically non-toxic.

Acute toxicity inhalation – key study

The key study on acute inhalation toxicity was carried out using Niacine. Niacine may be used in a read-across approach for Nicotinamide, as both compounds are convertible within the human body. The study was carried out according to OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class (ATC) Method). Groups of male and female rats were treated with Niacin at a concentration of 0.54, 1.1 or 3.8 mg/L air for 4 hours. The LC50 for 4-hour exposure of Niacin obtained in this study was greater than 3.8 mg/L air (chemically determined mean aerosol concentration), which was the highest achievable aerosol concentration. There was no indication of relevant sex-related differences in effects of the test item.

Acute toxicity dermal – key study

A study according to EU Method B.3 and OECD Guideline 402 (Acute Dermal Toxicity) was carried out. Nicotinamide was tested for acute toxicity after single dermal application to rabbits. The test substance, available as a white, crystalline powder, was moistened with water and placed on the shorn dorsal skin of 5 male and 5 female animals under occlusive conditions for 24 hours. The dose was 2000 mg/kg bw (limit concentration). The only sign of toxicity was a slight reddening of the application site detected immediately after removal of the patches. The finding was present in some animals up to the end of the observation period. Deaths did not occur. At necropsy no abnormal findings, except the slight reddening at the application site, were recorded. The LD 50 values for male as well as female rabbits were above 2000 mg/kg bw (limit test). Nicotinamide was considered practically non-toxic.

Justification for selection of acute toxicity – inhalation endpoint
The key study on acute inhalation toxicity was carried out using Niacine. Niacine may be used in a read-across approach for Nicotinamide, as both compounds are convertible within the human body. See section acute toxicity inhalation for additional detail on read-across justification.

Justification for classification or non-classification

Based on results obtained in acute toxicity testing the substance is not classified and labeled according to Regulation 1272/2008/EEC (CLP) and Directive 67/548/EEC (DSD).