N-(2-hydroxyethyl)stearamide

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not available

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Palmidrol

EC Number:

208-867-9

EC Name:

Palmidrol

Cas Number:

544-31-0

Molecular formula:

C18H37NO2

IUPAC Name:

N-(2-hydroxyethyl)hexadecanamide

Test material form:

solid

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Sprague-Dawley rats (Vivo Bio Tech Ltd), age: 6–7 weeks

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: water with Tween 80 (0.5% w/v) and carboxymethyl cellulose (1% w/v)

Details on oral exposure:

Preliminary tests found that the test substance was suitable for oral gavage by suspension in water with Tween 80 (0.5% w/v) as a surfactant and carboxymethyl cellulose (1% w/v) as a suspending agent.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses performed to verify the concentrations of the test substance in dosing formulations showed that they were within an acceptable range compared to their respective nominal concentrations.

Duration of treatment / exposure:

90 d

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

250 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

500 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

20 (10 males and 10 females)

Control animals:

yes

Details on study design:

Rats were divided into six groups. Four groups of 20 (10 males and 10 females) were treated for 90 d by oral gavage with the vehicle control, the low dose of 250 mg/kg bw/day, the mid dose of 500 mg/kg bw/day, or the high dose of 1000 mg/kg bw/day. An additional 10 animals (five males and five females) in the control and in the high-dose groups were allowed to recover for an additional 28 days.

Examinations

Observations and examinations performed and frequency:

Observations:

Mortality (daily), clinical signs (weekly),
Ophthalmological examinations: before study initiation and at study termination,
Neurological parameters: qualitative and quantitative assessment of sensory reactivity, grip strength, motor activity, frequency of urination, defecation, rearing, and landing foot splay,
Body weight and food consumption: weekly,
Samples for hematology and clinical chemistry analysis: taken just prior to sacrifice.

Hematological parameters include hematocrit, hemoglobin concentration, erythrocyte count, total and differential leukocyte count, platelet count, and blood clotting time.

Clinical chemistry determinations include sodium, potassium, glucose, total cholesterol, urea, blood urea nitrogen, creatinine, total protein and albumin, and two or more enzymes that indicate hepatocellular effects.

Urine samples taken during the last week before sacrifice are examined for appearance, volume, osmolality or specific gravity, pH, protein, glucose, and presence of blood or blood cells.

Sacrifice and pathology:

At study termination, gross necropsy is performed including complete external body examination and organ weights recorded for liver, kidneys, adrenals, testes, epididymides, uterus, ovaries thymus, spleen, brain, and heart. Histopathological examination is performed on tissue samples from: all gross lesions, representative brain regions, spinal cord at three levels, pituitary, thyroid, parathyroid, thymus, esophagus, salivary glands, stomach, small and large intestines (including Peyer’s patches), liver, pancreas, kidneys, adrenals, spleen, heart, trachea, lungs, aorta, gonads, uterus, accessory sex organs, female mammary gland, prostate, urinary bladder, lymph nodes, peripheral nerve, bone marrow section, skin, and eyes if changes were observed upon examination. Tissue samples are fixed in 10% neutral buffered formalin before embedding in paraffin wax. Sections of 5 μm thickness are stained with hematoxylin and eosin for microscopic examination.

Statistics:

The results were analyzed statistically with IBM SPSS Statistical Software (version 23). Following assessment of homogeneity, using Levene’s test, of body weight, food consumption, hematology, clinical chemistry, organ weight, and neurological examination data, different groups were subjected to one-way analysis of variance (ANOVA). Comparisons between treated and control groups were analyzed by t tests with variance evaluated at the 5% level of significance.

Results and discussion

Results of examinations

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

No clinical signs were found in any group other than respiratory rales in one control male (day 84 until termination at day 91) and one treated, mid-dose (500 mg/kg bw/d) male from day 80 until day 91; these observations were incidental, not dose-related, and of no toxicological significance.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The average weight of male animals in the high treatment recovery group, was less than the average of males in the control recovery group, a difference that was statistically significant (P < 0.05). Based on the combined data from all dose groups and food consumption data, it is concluded that consumption of the test substance did not have an adverse effect on body weight or body weight gain.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

The results are normal with no differences between control and treated groups except for elevated total WBC counts for the high-dose group at the end of the recovery period. Although statistically higher than concurrent controls, the value 10.08+E3/cm2 is well within the historical range for control rats in 90-day studies at the test facility.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

A few isolated measurements were statistically different from controls, but are considered to be incidental and without biological significance due to lack of any dose dependency as well as their values falling within ranges of the laboratory’s historical controls.

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

The only statistically significant difference in mean organ weights noted at end of the 90 d treatment was that of the relative, but not absolute, heart weight in females being lesser than the control, which in absence of dose dependence, was considered to be incidental. At the end of the 28 d recovery period, absolute and relative adrenal weights only in male rats were statistically higher in the high dose group as compared to controls, and absolute liver weights were significantly lower in the highest dose group females only than in control rats. These results appear to be incidental due to the lack of any changes in other correlated parameters, such as necropsy findings, histopathology findings, clinical hematology, and clinical chemistry.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Gross necropsy revealed an absence of any remarkable gross abnormalities in all but two male animals at the end of the 90 d treatment period and two males at the end of the 28 d recovery phase. One mid-dose rat had multiple abscesses in the lungs and another mid dose rat animal had underweight testes and epididymides. These incidental findings were found only in this group and are concluded to be unrelated to dosing with the test substance. Moderate splenic enlargement was found in two high dose males at the end of the recovery period, but subsequent histopathologic examination showed this to be due to splenic congestion, a common condition considered to be incidental in this case.

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

The evaluation of tissues and organs from control and high-dose groups showed no incidence of any remarkable findings that could be related to treatment due to lack of any dose dependency as well as their values falling within ranges of the laboratory’s historical controls. Single animals in different groups showed isolated (1 in 20 animals) findings.

Histopathological findings: neoplastic:

not specified

Other effects:

not specified

Effect levels

Key result

Dose descriptor:

NOEL

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

clinical signs

mortality

Target system / organ toxicity

Key result

Critical effects observed:

no

Any other information on results incl. tables

For detailed results tables kindly refer to the attached background materials section of the IUCLID.

Applicant's summary and conclusion

Conclusions:

Under the study conditions, the 90 d NOEL was considered to be 1000 mg/kg bw/day.

Executive summary:

A study was conducted to evaluate the repeated dose oral toxicity of the test substance, C16 MEA according to design based on OECD Guideline 408, in compliance with GLP. Preliminary tests found that the test substance was suitable for oral gavage by suspension in water with Tween 80 (0.5% w/v) as a surfactant and carboxymethyl cellulose (1% w/v) as a suspending agent. Sprague-Dawley rats were divided into six groups. Four groups of 20 (10 males and 10 females) were treated for 90 d by oral gavage with the vehicle control, the low dose of 250 mg/kg bw/day, the mid dose of 500 mg/kg bw/day, or the high dose of 1000 mg/kg bw/day. An additional 10 animals (five males and five females) in the control and in the high-dose groups were allowed to recover for an additional 28 d. The following observations and examinations were performed: mortality (daily), clinical signs (weekly), functional observations and locomotor activity (end of treatment), body weight and food consumption (weekly), clinical pathology (end of treatment), ophthalmological examinations (before study initiation and at study termination), macroscopy at termination, organ weights and histopathology on a selection of tissues. There were some incidental findings that are concluded to be unrelated to treatment and of no toxicological significance. No treatment-related adverse effects were found up to the highest tested dose level of 1000 mg/kg bw/day. Under the study conditions, the 90 d NOEL was considered to be 1000 mg/kg bw/day (Nestmann, 2016).