Xylitol

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1970

Materials and methods

Principles of method if other than guideline:

13-week oral diet study in rats

GLP compliance:

no

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Xylitol

EC Number:

201-788-0

EC Name:

Xylitol

Cas Number:

87-99-0

Molecular formula:

C5H12O5

IUPAC Name:

(2R,3r,4S)-pentane-1,2,3,4,5-pentol

Details on test material:

- Purity: not reported

Test animals

Species:

rat

Strain:

other: Charles River CD

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River
- Housing: individually caged
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13-weeks

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

5 000 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

10 000 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

20 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

8/sex/dose level

Control animals:

yes, plain diet

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Parameters examined: physical condition and behaviour

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean weekly diet consumption calculated as g food/kg body weight/week: Yes
- Compound intake calculated as averages from the consumption and body weight data: Yes

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: 4, 8 and 12 weeks
- Dose groups that were examined: all
- Parameters examined: eyelids, conjunctiva, and sclera, as well as examination of cornea, iris, lens, and fundus with an ophthalmoscope

HAEMATOLOGY: Yes
- Time schedule for collection of blood: 4, 8, 12 weeks
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 5/sex/dose group
- Parameters examined: haemoglobin content, haematocrit, total and differential leukocyte counts, and coagulation time

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: 4, 8 and 12 weeks
- Animals fasted: No data
- How many animals: 5/sex/dose group
- Parameters examined: blood glucose. In addition, at the time of sacrifice, blood was taken from 5 male and 5 female rats of each group for determination of serum alkaline phosphatase, serum glutamic pyruvic transaminase, serum glutamic oxalacetic transaminase, blood urea nitrogen, serum
bilirubin and uric acid values.

URINALYSIS: Yes
- Time schedule for collection of urine: 4, 8 and 12 weeks
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters checked examined: colour and transparency; pH and specific gravity; qualitative tests for glucose, albumin, ketones, bilirubin,
and occult blood; and urine sediment examined microscopically

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: prior to treatment and at 4, 8 and 12 weeks
- Dose groups that were examined: all
- Parameters examined: gait, body position, muscle tone, behaviour, movement of legs, and reflexes

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
- Gross autopsies were performed on all animals found dead or sacrificed at the end of the study. The extent of autopsy and histologic study was limited to grossly abnormal organs in the animals found dead or sacrificed prematurely. For animals sacrificed at the end of the study, the cervical, thoracic and abdominal organs plus the pituitary and brain were examined grossly. The heart, lungs, liver, kidneys, spleen, brain, ovaries, testes, uterus, thyroid gland, adrenal glands and pituitary gland were weighed for rats sacrificed at the end of the study. Of these, the thyroid glands, adrenal glands and pituitary glands were weighed after fixation in 1070 formalin. The other organs were weighed prior to fixation.

HISTOPATHOLOGY: Yes
- Portions of all the organs and other tissues observed at gross pathology were fixed in 10% formalin containing 2% acetate for histologic sectioning. Haematoxylin and eosin stained sections prepared included liver, spleen, kidney, heart, lung, adrenal, thyroid, pituitary, gonads, intestine, pancreas, urinary bladder, brain, bone marrow, and eye. Additional sections of liver and kidney were also stained with the P.A. Schiff stain. Frozen sections of liver were stained with oil red 0 stain.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Except for transient diarrhoea in a few of the treated animals, no clinical abnormalities that were related to treatment were noted. During the first week 10 animals fed compound at the level of 10 grams/kg/day showed some diarrhoea. The diarrhoea noted during week one cleared and did not recur except in one animal that had diarrhoea during week 4. Animals fed at higher and lower levels did not have diarrhoea except one high level animal had diarrhoea during week 7.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

One rat fed 5000 mg/kg/day died during the 6th week of the study with chronic pneumonia and a lung abscess. All animals at 10000 and 20000 mg/kg survived the entire study period.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight gain of treated animals, particularly the males was slightly less than that of controls at the end of the study. At the end of the study, the mean body weights of male and female rats fed the compound at the high level of 20 grams/kg/day and the mid-level of 10 grams/kg/day were significantly less than that of control animals.

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

Description (incidence and severity):

The left eye of one control rat was described as “cloudy” during week 12 and the lens was observed to be opaque. Except for this, no abnormalities were noted in the ophthalmic examinations.

Haematological findings:

no effects observed

Description (incidence and severity):

Some variations were observed; however, these did not persist for more than one time period or show any relation to dose level.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

Blood glucose values of treated and control animals showed no persistent difference. Except for slight elevations of the blood urea nitrogen and bilirubin in individual treated animals, none of the determinations performed on blood obtained at the time of sacrifice showed increased values for treated animals. In no animal was the blood urea nitrogen greater than 30 mg %. All bilirubin values were less than 0.8 % with the range for treated and control animals being the same. No animal had a uric acid level greater than 3.0 mg %.

Urinalysis findings:

no effects observed

Description (incidence and severity):

Tests for bilirubin, occult blood, and glucose were negative. The appearance of the specimens and the presence of cells and crystals in the specimens did not distinguish the urine of treated animals from that of controls. Calcium oxylate crystals were noted in only 2 treated animals at week 8.

Behaviour (functional findings):

no effects observed

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

AAs a reflection of the reduced mean body weights at 10 and 20 g/kg/day at the end of the study, there was a slight increase in the weight of the brain, liver, kidney, heart, spleen, and testes when these were expressed as a percent of body weight. Only the mean weight of the liver of treated female rats was absolutely increased over that of controls; however, this was not numerically significant.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Incidental lesions noted at necropsy included dilation of the uterus with fluid in the uterine cavity in 1 control rat and 3 rats at 20 g/kg. Chronic murine pneumonia with abscess formation was noted in 2 rats. Mural haemorrhage was noted in the intestine of one rat at 20 g/kg. Petechial haemorrhages were noted in the thymus of 5 test rats and all the control male rats. The later alteration may have been an agonal phenomenon related to the technique of decapitation.

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Incidental lesions were primarily focal inflammatory lesions. Many of the animals had focal collections of lymphocytes in the liver and kidney; occasional sporadic cases of pyelonephritis, and bronchopneumonia, or pulmonary abscesses were found. These findings appeared randomly throughout all animals including controls and were not dose related. Two animals (one control and one high dose animal), had focal inflammatory lesions in the brain. These focal inflammatory lesions were of the type that one encounters incidentally in series of rats and are considered to be of no toxicologic significance. Several animals showed focal interstitial oedema in the testes; this finding is non-specific.

Histopathological findings: neoplastic:

no effects observed

Effect levels

Dose descriptor:

NOAEL

Effect level:

20 other: grams/kg/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Highest dose level tested

Target system / organ toxicity

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

13-Week NOAEL: 20 g/kg/day (highest dose tested)

Executive summary:

In a 13-week study four groups of eight female and eight male Charles River CD rats were fed 0, 5, 10 and 20 g dietary xylitol/kg/day. Each rat was observed daily to determine general condition and behaviour. Food consumption and body weights were measured weekly and the test material intake calculated. Ophthalmic and neurologic examinations were performed on all rats prior to treatment and at 4, 8 and 12 weeks. Haematological studies, blood glucose determinations and urinalyses were performed on specimens from 5 male and 5 female rats from each group at 4, 8 and 12 weeks. Serum alkaline phosphatase, serum glutamic oxalacetic transaminase, blood urea nitrogen, serum bilirubin and uric acid were determined on blood from 5 male and 5 female animals of each group at 13 weeks. Each surviving animal was autopsied at that time.
All animals fed compound at the level of 10 and 20 grams/kg/day survived the entire period of the study. One rat fed the low level of 5 grams/kg/day died during the 6th week of the study with chronic pneumonia and a lung abscess. Body weight gain of treated animals, particularly the males was slightly less than that of controls at the end of the study. At the end of the study, the mean body weights of male and female rats fed the compound at the high level of 20 grams/kg/day and the mid-level of 10 grams/kg/day were significantly less than that of control animals. As a reflection of decreased body weight there was a slight increase in the weight of the brain, liver, kidney, heart, spleen, and testes when expressed as a percent of body weight. Only the mean weight of the liver of treated female rats was absolutely increased over that of the controls; however, this was not numerically significant. Except for transient diarrhoea in a few of the treated animals, no clinical abnormalities that were related to treatment were noted. Clinical laboratory studies did not distinguish treated animals from controls. Autopsy of all animals failed to demonstrate any lesions related to the level of compound given in the diet. Incidental inflammatory lesions were noted in rats of all groups.
Rats fed xylitol as a dietary admix at levels of 5, 10 and 20 grams/kg/day for 13 weeks tolerated the feeding well except for transient diarrhoea and slightly reduced weight gains.