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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
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:
1992

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method B.31 (Prenatal Developmental Toxicity Study)
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Qualifier:
according to
Guideline:
other: U.s. Food and Drug Administration (1964) Redbook
GLP compliance:
yes (incl. certificate)
Remarks:
Life Science Research Ltd
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
- Name of test material: Nicotinic acid

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 10 to 11 weeks
- Weight at study initiation: 222 to 269 g
- Fasting period before study: None
- Housing: TR18 cages from Modular Systems Limited, London, England and RB3 modified cages from North Kent Plastics Limited, Dartford, Kent, England. The cages consisted of stainless steel (TR18) or high density polypropylene (RB3) bodies with lids and floors of stainless steel grid and were suspended in batteries over trays covered with absorbent crepe paper which was replaced twice weekly or daily during pairing.
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature: 21°C (range 18 - 25 °C)
- Humidity: 55 % (range 40 - 70 %)
- Air changes: 15 per hr
- Photoperiod: 12 hrs dark / 12 hrs light

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Remarks:
0.5 % in water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:

DIET PREPARATION
- Rate of preparation of diet (frequency): P0076 was prepared freshly each day as a suspension in 0.5 % (w/v) aqueous methylcellulose mucilage. Dosages were of the material as supplied.

VEHICLE
- Amount of vehicle (if gavage): Volume-dosage of 10 ml/kg.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Samples of each concentration of the test mixtures were taken during the first and last weeks of treatment and analysed by Life Science Research for test material content.
Details on mating procedure:
- Impregnation procedure: Cohoused
- M/F ratio per cage: At various stages of the study the maximum number of rats per cage was:
Stage, Number of rats (M/F), Cage type
Acclimatisation, 0 M up to 5 F, TRI8
Mating, 1M 1F, RB3 modified
Gestation,0M 1F, RB3 modified
- Mating procedure: Females were paired on a one-to-one basis with stock males of the same strain. Each morning following pairing, the trays beneath the cages were checked for ejected copulation plugs and a vaginal smear was prepared from each female and examined for the presence of spermatozoa. The day on which a sperm positive vaginal smear or at least three copulation plugs were found was designated Day 0 of gestation.
- Verification of same strain and source of both sexes: Yes
- Proof of pregnancy: Vaginal plug and sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
Group, Treatment, Dose level (mg/kg/day), Number of animals, Animal numbering
1, Control, 0, 22, 1-21
2, Test item, 40, 22, 23-44
3, Test item, 200, 22, 45-66
4, Test item, 1000, 22, 67-88
The animals were dosed daily by the oral route (gavage) from Day 6 to Day 15 of gestation. Control animals received the vehicle at the same volume-dosage during the treatment period. The volume administered daily to each animal was based on the animal's bodyweight on that day.
Frequency of treatment:
Daily
Duration of test:
Day 20 of gestation.
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 40, 200, 1000 mg/kg bw/day
Basis:
analytical conc.
No. of animals per sex per dose:
22 animals
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The preliminary teratology study in the rat was conducted using dose levels of 0, 40, 200 and 1000 mg/kg/day. At 1000 mg/kg/day, the rate of bodyweight change was slightly lower than that of the Controls during the treatment period.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed daily throughout the study and any visible signs of reaction to treatment were recorded, with details of type, severity, time of onset and duration.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes
- Time schedule for examinations: Females were weighed on Days 0, 3, 6 to 16 inclusive, 18 and 20 of gestation.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: Each animal was first examined macroscopically for evidence of disease or adverse reaction to treatment and specimens of abnormal tissues were retained.
The reproductive tract, complete with ovaries, was dissected out and the following recorded:
a) Number of corpora lutea in each ovary (assessed before removal);
b) Number of implantation sites;
c) Number of resorption sites {classified as early or late};
d) Number and distribution of foetuses in each uterine horn.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Number and distribution of foetuses in each uterine horn
Fetal examinations:
- External examinations: Yes, all per litter
- Soft tissue examinations: Yes, all per litter
- Skeletal examinations: Yes, all per litter
- Head examinations: Yes, all per litter

- External examination at necropsy: Each foetus was weighed, sexed and examined for any external abnormalities. Individual placental weights and placental abnormalities were recorded.
- Internal examination at necropsy: The neck and the thoracic and abdominal cavities of approximately half of each litter were dissected and examined. All foetal abnormalities were recorded and the offspring eviscerated prior to fixation in industrial methylated spirit (74° o.p.).
- Internal examination by free-hand serial sectioning: The remaining foetuses in each litter were placed in Bouin's fixative. After a period of fixation they were examined by the Wilson free-hand serial sectioning technique (Wilson, J.G. Teratology: Principles and Techniques, p.251, University of Chicago Press, 1965).
- Skeletal examinations: The eviscerated foetuses were processed and stained with Alizarin-red, using a modification of the Dawson staining technique (Tesh, J.M., Ph.D. Thesis, Faculty of Veterinary Science, University of Liverpool, 1968), and the skeletons were examined.
Statistics:
- Statistical evaluation: The significance of suggestive inter-group differences was tested using appropriate statistical tests, each of which has been specified where used. Differences with an associated probability of P<0.05 were considered to be statistically significant.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes. Remark: Slightly depressed body weight gains.

Details on maternal toxic effects:
- General condition and mortality: The general condition of the females was unaffected by treatment with test item, and no deaths occurred.
- Bodyweight: Bodyweight gain by females in Group 4 (1000 mg/kg/day) was slightly lower than that of the Controls during treatment. Weight gain of females in Groups 2 and 3 (40 and 200 mg/kg/day) was similar to that of the Controls throughout gestation.
- Food and water intake: Food and water intake were unaffected by treatment.
- Necropsy findings: Necropsy of females on Day 20 of gestation revealed no treatment-related macroscopic findings.
- Formulation analysis: Acceptable homogeneity of the formulation was demonstrated at 4 and 100 mg/mL, and the test item was shown to be stable in 0. 5% (w/v) aqueous methylcellulose mucilage for at least six hours. Satisfactory concentrations of preparations taken during the first and last weeks of treatment were obtained.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
198 mg/kg bw/day (actual dose received)
Based on:
other: Nicotinamide equivalent
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEL
Effect level:
198 mg/kg bw/day (actual dose received)
Based on:
other: Nicotinamide equivalent
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
- Litter responses: Litter responses, as assessed by the numbers of implantations, resorptions and viable young, and the extent of pre- and post-implantation losses, were unaffected by treatment with test item. Mean foetal and placental weights in Group 4 (1000 mg/kg/day) were slightly lower than those of the concurrent Controls and the difference was statistically significant for the weight of male foetuses and for placental weight. However, all Group 4 values fell within the background control range. Groups 2 and 3 (40 and 200 mg/kg/day) were unaffected by treatment.
- Foetal evaluation: Macroscopic examination of foetuses at necropsy, and following skeletal processing or free-hand serial sectioning revealed a number of observations, the majority of which were of types and occurred at frequencies previously recorded in Control foetuses of this strain of rat at these laboratories, and showed no association with treatment.
In Group 3 (200 mg/kg/day), nine foetuses from three litters (2.8 %) were seen to have squat appearance and limb flexures; seven of these allocated to skeletal examination had thickened ribs. However, subsequent to this study, similar abnormalities have been observed in Control foetuses from other studies (up to 6.1% in July 1991, with four further occurrences (1.8%) up to October 1991). The present findings are, therefore considered unlikely to be a result of maternal treatment with test item.
In Group 4 (1000 mg/kg/day) there was a slight increase in the incidence of foetuses with incompletely ossified parietal or basisphenoid bones; in both cases the values just exceeded the upper limit of the background control ranges. In the absence of any other reductions in skeletal ossification, it was considered unlikely that these findings were related to treatment with test item.
A small number of foetuses showed more complex or unusual morphological changes:
Control: One foetus with digits of left fore-paw flexed. One foetus with a small additional
plaque of bone in the parietal suture.
Group 2 (40 mg/kg/day): One foetus with one abnormal fore-paw and an inter-ventricular septal defect.
Group 3 (200 mg/kg/day). Two foetuses with unilateral slight macrophthalmia.
Group 4 (1000 mg/kg/day). One foetus with unilateral slight macrophthalmia.
The group distribution and incidence of these findings did not suggest any treatment-related involvement.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The NOAEL for maternal toxicity derived from this study was 200 mg/kg bw/d based on effects on body weight (equivalent to 198 mg/kg bw/day for nicotinamide). The NOAEL on reproduction toxicity and developmental toxicity is 200 mg/kg bw/day (equivalent to 198 mg/kg bw/day Nicotinamide) based on the significantly decreased placental and pup body weight (males only). No teratogenic effects were observed.
Executive summary:

A study was carried out according to EU Method B.31, OECD Guideline 414 (Prenatal Developmental Toxicity Study) and U.S. Food and Drug Administration (1964) Redbook. The influence of the test item upon the progress and outcome of pregnancy was assessed in sexually mature rats of the CD strain. For this purpose, the test item was administered by gavage at dose levels of 40, 200 or 1000 mg Nicotinic acid/kg/day to groups of 22 pregnant rats from Day 6 to Day 15 of gestation inclusive. Equivalent Nicotinamide doses are 40, 198 and 990 mg Nicotinamide/kg bw/day. Control animals received the vehicle, 0.5 % (w/v) aqueous methylcellulose throughout the same period. All females were killed on Day 20 of gestation for examination of their uterine contents. The general condition of females was similar in all groups, and no deaths occurred. Bodyweight gain of females receiving 1000 mg/kg/day was slightly depressed during the treatment period. Food and water intakes of females in all treated groups were unaffected by treatment. No adverse treatment-related macroscopic changes were observed at necropsy of females on Day 20 of gestation. Litter size and survival were unaffected by treatment. Foetal and placental weights were slightly lower than those of the controls at 1000 mg Nicotinic acid/kg/day (equivalent to 990 mg Nicotinamide/kg bw/day). Foetal examinations at necropsy and following skeletal processing or free-hand serial sectioning revealed no morphological changes that were considered to be related to treatment with test item.

It was concluded from this investigation that oral administration of the test item to pregnant rats during the period of organogenesis at dose levels up to 200 mg Nicotinic acid/kg/day (equivalent to 198 mg Nicotinamide/kg bw/day) was without adverse effect upon maternal condition and weight gain or upon litter and foetal responses. At 1000 mg Nicotinic acid/kg/day (equivalent to 990 mg Nicotinamide/kg bw/day) maternal bodyweight gain was slightly depressed, and foetal and placental weights were slightly lower than those of the Controls. However, there were no indications of any adverse effects upon survival or morphological development in utero.