Nicotinamide

Acute Toxicity: inhalation

Administrative data

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.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Report date:

2012

Materials and methods

Test guideline

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

Test material

Test material information

Constituent 1

Reference substance name:

Nicotinic acid

EC Number:

200-441-0

EC Name:

Nicotinic acid

Cas Number:

59-67-6

IUPAC Name:

nicotinic acid

Test material form:

solid: crystalline

Details on test material:

- Name of test material: Nicotinic acid

Test animals

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

Administration / exposure

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.

Results and discussion

Effect levels

Effect levels 1

Sex:

male/female

Dose descriptor:

LC0

Effect level:

3.8 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Effect levels 2

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.

Applicant's summary and conclusion

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.