Desmedipham

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1985-02-04 to 1985-11-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Pre-dates test guideline but broadly comparable to guideline.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EPA OPP 82-1 (90-Day Oral Toxicity)

Version / remarks:

1982

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1981

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Desmedipham

EC Number:

237-198-5

EC Name:

Desmedipham

Cas Number:

13684-56-5

Molecular formula:

C16 H16 N2 O4

IUPAC Name:

ethyl 3´-phenylcarbamoyloxycarbanilate

Test material form:

solid: particulate/powder

Details on test material:

The test material is Desmedipham.

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Wistar rat, KFfl-han., outbred, SPF quality. Standard species/strain with historical control data available.

Sex:

male/female

Details on test animals or test system and environmental conditions:

Age (at delivery): 6 weeks.
Body weight and range (at pre-test) males-. 68-100 g females-. 58- 86 g
Identification Cage number and individual ear tags.
Randomization Computer-generated random algorithm.
Acclimation 7 respectively 5 days under test conditions, after veterinary examination.
Conditions Optimum Hygienic Conditions behind a barrier system. Air-conditioned with 10 - 15 air changes per hour, and hourly monitored environment with temperature 22 +/-2 degrees centigrade, relative humidity 55 +/-1QX, 12 hours artificial fluorescent light/12 hours dark, music/light period.
Accommodation Groups of 5 in Makrolon type-4 cages with sterilized standard softwood bedding (Lignocell, Schill A6, Switzerland). Bedding was autoclaved at 120 degrees centigrade for 60 minutes before use.
Diet Pelleted standard Kliba 343 rat maintenance diet ('Kliba', Klingentalmuehle. AG, Switzerland) ad libitum. Results of analysis for contaminants are included in the report (Attachment, see pp. 243-249).
Water Tap water, ad libitum. Results of analyses for contaminants are included in the report (Attachment, see pp. 239-242).

Administration / exposure

Route of administration:

oral: feed

Details on route of administration:

DESMEDIPHAM TECHNICAL mas mixed with micro-granulated feed. Water <1:10 volume/weight ratio) was added to aid pelleting. The pellets were dried for 48 hours before storage.

Vehicle:

water

Details on oral exposure:

Method Oral, by feed admixture.
Frequency Ad libitum
Duration of acclimation period: 5 days under test conditions, with veterinary examination.
Duration of treatment 13 weeks.
Duration of recovery 4 weeks.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Homogeneity and content of the test article in the feed were determined before test initiation and at monthly intervals. Analyses were performed in the RCC Analytical Chemistry Laboratory, according to a method supplied by the sponsor. Stability analyses were performed in RCC Project 015153. An additional stability test was initiated and performed at the beginning of the treatment phase.

Duration of treatment / exposure:

13 weeks.

Frequency of treatment:

Continuous in diet.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm

Remarks:

Control: basal diet

Doses / concentrations 2

Dose / conc.:

6 ppm

Doses / concentrations 3

Dose / conc.:

30 ppm

Doses / concentrations 4

Dose / conc.:

60 ppm

Doses / concentrations 5

Dose / conc.:

300 ppm

No. of animals per sex per dose:

25

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: Based upon a previous 13-week feeding study in rats no clear NOAEL established.
- Fasting period before blood sampling for clinical biochemistry: Samples for hematology, clinical biochemistry and urinalysis were taken from all scheduled animals of each sex and group which were fasted overnight (18-hour period) at 4/5, 9 and 12/13 weeks of treatment, and from all animals of the recovery group prior to sacrifice, at 16/17 weeks.

Positive control:

Not required for this study type

Examinations

Observations and examinations performed and frequency:

Observations for clinical signs and symptoms of toxicity were performed twice daily, a.m. and p.m. In addition to the daily observations, each rat had a weekly detailed clinical examination which included a palpation for tissue masses. A description of any lesion or mass observed at any examination was recorded and the subsequent progress was monitored.
FOOD CONSUMPTION The food consumption was recorded for 7-day periods and the mean daily food consumption calculated. These data were recorded weekly.
WATER CONSUMPTION Water consumption was monitored by daily visual appraisal of the water bottles. During week 11, the water consumption of all animals was measured quantitatively.
BODY WEIGHTS The body weight of each animal was recorded weekly.
OPHTHALMOSCOPIC EXAMINATIONS Qphthalmoscopic examinations were performed on ten animals per sex and group. A description of any abnormality was recorded. Examinations were performed at pretest, at 13 weeks of treatment and at the end of the recovery period.
ORGAN WEIGHTS
The following organ weights were recorded of all animals necropsied at the end of treatment and after the recovery period-. adrenal glands, brain, heart, kidneys, liver, ovaries, pituitary gland, spleen, testes, thyroid gland.

NECROPSY AND HISTOPATHOLOGY
Necropsy was performed on all rats. Tissue specimens were fixed in 4% neutral phosphate buffered formalin, processed and embedded in paraffin. Sections were cut at an approximate thickness of 4 micrometers and stained with hematoxylin and eosin.
Sections of the following organs/tissues were examined microscopically (number of sections per organ) •.
Adrenal glands <2>, aorta (thoracic, 1>, bone (sternum, 1), bone marrow (sternum, 1> , brain (3) , cecum (1>, colon (1) , duodenum (1), epididymides (2), esophagus (1), eyes (2), Harderian glands (2), heart (1), ileum (1), jejunum (1), kidneys (2), liver (2), lungs (2), lymph nodes (mandibular, mesenteric, 1), mammary gland (1), ovaries (2>, pancreas (1) , parathyroid glands (uiherever possible, 2), pituitary gland (1), prostate (1), rectum (1), salivary glands (1), sciatic nerve (i), seminal vesicles (2), skeletal muscle (1), skin (1), spinal cord (1>, spleen (1), stomach (1), testes (2), thymus (wherever passible, 1), thyroid gland (2), tongue (1), trachea (1), urinary bladder 01 > , uterus (3), and all gross lesions.
From all rats, lungs, liver, kidneys, and gross lesions were examined. The other organs were examined only from the rats of groups 1 and 5 that were killed at the end of the administration period (K0).

Sacrifice and pathology:

Fifteen rats per sex and group were killed after a treatment period of 13 weeks and 10 rats per sex and group were killed after an additional treatment-free period of 4 weeks.

Statistics:

The following statistical methods were used to analyze the body weights, food consumption, water consumption, organ weights and clinical laboratory data: Univariate one-way analysis of variance was used to assess the significance of intergroup differences. If the variables could be assumed to follow a normal distribution, the Dunnett-test (many to one t-test) based on a pooled variance estimate was applied for the comparison between the treated groups and the control groups. The Steel-test (many-one rank test) was applied when the data could not be assumed to follow a normal distribution. For the overall spontaneous mortality data, the Fisher's exact test for 2x2 tables was applied. Group means were calculated for continous data and medians were calculated for discrete data (scores) in the summary tables. Individual values, means, standard deviations and statistics were rounded off before printing. For example, test statistics were calculated on the basis of exact values for means and pooled variances and then rounded off to two decimal places. Therefore, two groups may display the same printed means for a given parameter, yet display different test statistics values.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No treatment-related clinical symptom or sign of toxicity was evident.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

No treatment-related death was observed during this study one male of the control group (no. 9) died spontaneously during this study. The cause of death remains unclear.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

The body weight gain of all treated animals was unaffected by the treatment with DESMEDIPHAM TECHNICAL.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

The food consumption of the treated and the control groups were comparable.
The mean daily nominal test article consumption during the reported 13 weeks of treatment was 0.5, 2.6, 5.2 and 26 mg/kg body weight for males and 0.5, 2.7, 5.6 and 27 mg/kg body weight for females of treatment groups 2, 3, 4 and 5, respectively.

Food efficiency:

not examined

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

no effects observed

Description (incidence and severity):

The mean water consumption of the treated and control groups was comparable.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No treatment-related findings were noted.

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

The assessment of hematological data indicated slight toxic methemoglobinemia and a compensatory erythrogenic response during the 13 weeks of treatment. The effects observed were-.
- slightly increased methemoglobin formation for male and female rats of group 5 at each time point during the treatment,
- minimally increased reticulocyte count for both sexes of group 5 at 9 weeks and for male rats of group 5 at 12/13 weeks of treatment.
Recovery phase-.
- slightly increased methemoglobin level for male rats of group 5 at 16/17 weeks,
- minimally increased reticulocyte count for both sexes of group 5 at 16/17 weeks.
These results indicate that DESMEDIPHAM TECHNICAL induces a slight oxidative attack on circulating erythrocytes with an accompanying increase in circulating reticulocytes . The effects were not cumulative to the extent that the body's normal adaptive mechanisms (such as increased erythropoiesis) would be overloaded, resulting in irreversible damage, nor were Heinz bodies observed. At the termination of the treatment-free period, reversible changes were noted in the methemoglobin levels for both sexes of group 5, however, for the male rats the findings were significantly greater than those of the controls .
All other statistical differences in the results of the hematological parameters were considered to be incidental and of normal biological variation

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

The assessment of biochemical data indicated slightly lower T4 values for both sexes of group 5 at 12/13 weeks of treatment, and for the male rats of group 5 at termination of the treatment-free period, at 16/17 weeks. All other statistical differences in the results of the biochemical parameters were considered to be incidental and of normal biological variation

Endocrine findings:

not examined

Urinalysis findings:

no effects observed

Description (incidence and severity):

The assessment of urinalysis data indicated no treatment related changes at 4/5 weeks and 12/13 weeks of treatment, nor at termination of the treatment-free period at 16/17 weeks. All differences in the results of the urinalysis parameters were considered to be incidental and of normal biological variation.

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):

At the end of the application period - after 13 weeks - a minimal decrease in the mean absolute and organ to brain weight ratio was noted for the pituitary of female rats in groups 4 and 5. These weight changes are interpreted as being incidental because no clear dose relationship could be seen, and neither gross nor histological alterations were present. This is also true for the altered liver weight in group 3 and 4 female rats as for the altered heart weight of the females in group 4. Because of a technical error, the organ weights at the end of the recovery period were not considered to be an accurate reflection of the actual organ weights and therefore not included in this report. However, the organ weights of the animals sacrificed after the treatment period showed no treatment-related differences between the control and treated groups. No treatment-related macro- and microscopic findings were noted in either the 13-week or 17- week sacrifice interval.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No treatment-related macroscopic findings were observed. A few spontaneous gross lesions were encountered in both control and treated rats.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

A few spontaneous microscopic lesions were observed at a random incidence in various organs of both control and treated rats.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not examined

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

30 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

haematology

Remarks on result:

other: Equivalent to achieved mean intakes of 2.6 and 2.7 mg/kg bw/d un males and females respectively

Target system / organ toxicity

Key result

Critical effects observed:

no

Lowest effective dose / conc.:

60 ppm

System:

other: Target system / organ toxicity Other: Erythrocyte (Met-Hb formation)

Organ:

other: Erythrocyte (Met-Hb formation)

Any other information on results incl. tables

See results tables attachment for details.

Applicant's summary and conclusion

Conclusions:

A NOAEL of 30 ppm (2.6-2.7 mg/kg bw/d) was determined for this study based on haematological changes at 60 ppm.

Executive summary:

In this 13-week oral toxicity (feeding) study, DESMEDIPHAM TECHNICAL was administered in the feed to Wistar rats. The study was comprised of five groups, each containing 25 male and 25 female rats.  Ten animals per sex and dose group were observed for an additional recovery period of four weeks.  No treatment-related death was observed. One male of the control group died spontaneously during this study. No treatment-related clinical signs of toxicity were noted.  Body weights, food and water consumption were unaffected by treatment. The mean daily test article consumption was 0.5, 2.6, 5.2 and 26 mg/kg bw/d for males; 0.5, 2.7, 5.6 and 27 mg/kg bw/d for females.  Ophthalmoscopy did not reveal any treatment-related findings.  Haematological data indicated slight toxic methemoglobinemia and a compensatory erythrogenic response during the 13 weeks of treatment.  Clinical chemistry data indicated slightly lower T4 values for both sexes of group 5 at 12/13 weeks of treatment, and for the male rats of group 5 at termination of the recovery phase.  Urinalysis data indicated no treatment-related changes.
No treatment-related organ weight changes were observed either after 13 weeks or after 17 weeks of the experiment.  No treatment-related macroscopic and microscopic findings were observed after 13 and 17 weeks, respectively.  A NOAEL of 30 ppm (2.6-2.7 mg/kg bw/d) was determined for this study based on haematological changes at 60 ppm.