Pyridinium, 1-[[(6R,7R)-7-[[(2Z)-(2-amino-4-thiazolyl)[(1-carboxy-1-methylethoxy)imino]acetyl]amino]-2-carboxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl]methyl]-, chloride, hydrochloride (1:1:1)

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Reference substance 001

Cas Number:

73547-70-3

Molecular formula:

C22-H22-N6-O7-S2.2 H-Cl

Specific details on test material used for the study:

Identification : Ceftazidime dihydrochloride
Identification Number : 73547-70-3 (CAS number)
Physical State/Appearance : White powder
Assigned Purity (%w/w) - dry : 99.2% w/w (as dihydrochloride)
Assigned Purity (%w/w) : 95.663% w/w (as dihydrochloride)
Batch Number : G317308
Storage Conditions : Store in darkness and cold (approximately 4 °C);
used/formulated in light and at ambient temperature
(10 to 30 °C)
Expiry Date : 26 October 2018
Re-Test Date : 26 October 2018

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Wistar Han™:RccHan™:WIST

Sex:

male/female

Details on test animals or test system and environmental conditions:

A sufficient number of male and female Wistar Han™:RccHan™:WIST strain rats were
obtained from Envigo RMS (UK) Limited, Blackthorn, Bicester, Oxon, UK. On receipt the
animals were examined for signs of ill-health or injury. The animals were acclimatized for
nineteen days during which time their health status was assessed. Following the day of
arrival, vaginal smears were performed for all females throughout the acclimatization period
and females considered not showing appropriate estrous cycling activity were excluded from
treatment groups at least five days before the start of treatment. A total of ninety six animals
(forty eight males and forty eight females) were accepted into the study. At the start of
treatment the males weighed 286 to 367g, and were approximately eleven weeks old. The
females weighed 194 to 231g, and were approximately fourteen weeks old.
3.3.2 Animal Care and Husbandry
Initially, all animals were housed in groups of three in solid floor polypropylene cages with
stainless steel mesh lids and softwood flake bedding (Datesand Ltd., Cheshire, UK). During
the pairing phase, animals were transferred to polypropylene grid floor cages suspended over
trays lined with absorbent paper on a one male: one female basis within each dose group.
Following evidence of successful mating, the males were returned to their original cages.
Mated females were housed individually during gestation and lactation in solid floor
polypropylene cages with stainless steel mesh lids and softwood flakes.
The animals were allowed free access to food and water. A pelleted diet (Rodent 2018C
Teklad Global Certified Diet, Envigo RMS (UK) Limited, Oxon, UK.) was used. A
certificate of analysis of the batch of diet used is given in Annex 6. Mains drinking water
was supplied from polycarbonate bottles attached to the cage. Environmental enrichment
was provided in the form of wooden chew blocks and cardboard fun tunnels (Datesand Ltd.,
Cheshire, UK) except for paired animals and mated females during gestation and lactation.
Mated females were also given softwood flakes, as bedding, throughout gestation and
lactation. The diet, drinking water, bedding and environmental enrichment was considered
not to contain any contaminant at a level that might have affected the purpose or integrity of
the study.
The animals were housed in a single air-conditioned room within the Envigo Research
Limited, Shardlow, UK Barrier Maintained Rodent Facility. The rate of air exchange was at
least fifteen air changes per hour and the low intensity fluorescent lighting was controlled to
give twelve hours continuous light and twelve hours darkness. Environmental conditions
were continuously monitored by a computerized system, and print-outs of hourly
temperatures and humidities are included in the study records. The Study Plan target ranges
for temperature and relative humidity were 22 ± 3 °C and 50 ± 20% respectively. Short term
deviations from these targets were considered not to have affected the purpose or integrity of
the study; see deviations from Study Plan.
The animals were randomly allocated to treatment groups using a stratified body weight
randomization procedure and the group mean body weights were then determined to ensure
similarity between the treatment groups. The cage distribution within the holding rack was
also randomized. The animals were uniquely identified within the study by an ear punching
system routinely used in these laboratories.

Administration / exposure

Route of administration:

oral: gavage

Details on route of administration:

The test item was administered daily by gavage using a stainless steel cannula attached to a
disposable plastic syringe. Control animals were treated in an identical manner with 4 mL/kg
of Polyethylene glycol 400.
The volume of test and control item administered to each animal was based on the most
recent scheduled body weight and was adjusted at weekly intervals.

Vehicle:

polyethylene glycol

Remarks:

400mw avg

Details on oral exposure:

For the purpose of this study the test item was prepared at the appropriate concentrations as a
suspension in Polyethylene glycol 400. The stability and homogeneity of the test item
formulations were determined by Envigo Research Limited, Shardlow, UK, Analytical
Services. Results showed the formulations to be stable for two hours at 2.5, 12.5 and 50
mg/mL and for thirteen days at 187.5 mg/mL. Formulations were therefore prepared daily
for the low and intermediate dose levels and weekly for the high dose level and stored at
approximately 4 ºC in the dark.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of test item formulations were taken on two occasions and analyzed for
concentration of Ceftazidime dihydrochloride at Envigo Research Limited, Shardlow, UK,
Analytical Services. The results indicate that the prepared formulations were 95-107% of
the nominal concentration.

Duration of treatment / exposure:

Groups of twelve male and twelve female animals were treated daily at the
appropriate dose level throughout the study (except for females during parturition
where applicable). The first day of dosing was designated as Day 1 of the study.
doing continued until Day42 for Males and Day 13 post partum for females.

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

250 mg/kg bw/day (actual dose received)

Doses / concentrations 4

Dose / conc.:

750 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

12 (twelve)

Control animals:

yes, concurrent vehicle

Details on study design:

The animals were randomly allocated to treatment groups using a stratified body weight
randomization procedure and the group mean body weights were then determined to ensure
similarity between the treatment groups. The cage distribution within the holding rack was
also randomized. The animals were uniquely identified within the study by an ear punching
system routinely used in these laboratories.

Positive control:

N/A

Examinations

Observations and examinations performed and frequency:

Serial Observations
General Observations/Measurements

Clinical Observations
All animals were examined for overt signs of toxicity, ill-health and behavioral change
immediately before dosing, soon after dosing, and one hour after dosing during the working
week (except for females during parturition where applicable). All observations were
recorded.

Body Weight
Individual body weights were recorded on Day 1 (prior to dosing) and then weekly for males
until termination and weekly for females until pairing. During pairing phase females were
weighed daily until mating was confirmed. Body weights were then recorded for females on
Days 0, 7, 14 and 20 post coitum, and on Days 1, 4, 7 and 14 post partum. Body weights
were also recorded at terminal kill.
Normal range data for body weight changes for males and females during pre-pairing, and
males post-pairing are shown in Annex 8. Normal range data for body weight changes in
pregnant and lactating females are shown in Annex 9.

Food Consumption
During the pre-pairing period, weekly food consumption was recorded for each cage of
adults. This was continued for males after the mating phase. For females showing evidence
of mating, food consumption was recorded for the periods covering post coitum Days 0-7,
7-14 and 14-20. For females with live litters, food consumption was recorded for the periods
covering post partum Days 1-4, 4-7 and 7-14.
Food efficiency (the ratio of body weight change/dietary intake) was calculated
retrospectively for males throughout the study period (with the exception of the mating
phase) and for females during the pre-pairing phase. Due to offspring growth and milk
production, food efficiency could not be accurately calculated during gestation and lactation.

Water Consumption
Water intake was observed daily by visual inspection of water bottles for any overt changes.

Specialist Evaluations

Functional Observations
Prior to the start of treatment and at approximately weekly intervals thereafter, all animals
were observed for signs of functional/behavioral toxicity. These observations were
performed on mated females on Days 4, 11 and 18 post coitum and for littering females on
Days 4 and 12 post partum. Functional performance tests were also performed on five
selected males and females from each dose level, prior to termination, together with an
assessment of sensory reactivity to various stimuli.

Behavioral Assessment
Detailed individual clinical observations were performed for each animal using a purpose
built arena. The following parameters were observed:
Gait
Hyper/Hypothermia
Tremors
Skin color
Twitches
Respiration
Convulsions
Palpebral closure
Bizarre/Abnormal/Stereotypic behavior
Urination
Salivation
Defecation
Pilo-erection
Transfer arousal
Exophthalmia
Tail elevation
Lachrymation

This test was developed from the methods used by Irwin (1968) and Moser et al (1988). The
scoring system used is outlined in The Key to Scoring System and Explanation for
Behavioral Assessments and Sensory Reactivity Tests.

Functional Performance Tests
Motor Activity. Purpose-built 44 infra-red beam automated activity monitors were used to
assess motor activity. Animals were randomly allocated to the activity monitors. The tests
were performed at approximately the same time on each occasion (at least two hours after
dosing), under similar laboratory conditions. The evaluation period was thirty minutes for
each animal. The percentage of time each animal was active and mobile was recorded for the
overall thirty minute period and also during the final 20% of the period (considered to be the
asymptotic period, Reiter and Macphail, 1979)
.
Forelimb/Hindlimb Grip Strength. An automated meter was used. Each animal was allowed
to grip the proximal metal bar of the meter with its forepaws. The animal was pulled by the
base of the tail until its grip was broken. The animal was drawn along the trough of the meter
by the tail until its hind paws gripped the distal metal bar. The animal was pulled by the base
of the tail until its grip was broken. A record of the force required to break the grip for each
animal was made. Three consecutive trials were performed for each animal. The assessment
was developed from the method employed by Meyer et al (1979).

Sensory Reactivity
Each animal was individually assessed for sensory reactivity to auditory, visual and
proprioceptive stimuli. This assessment was developed from the methods employed by Irwin
(1968) and Moser et al (1988).
The following parameters were observed:
Grasp response
Touch escape
Vocalization
Pupil reflex
Toe pinch
Blink reflex
Tail pinch
Startle reflex
Finger approach

Hematology
The following parameters were measured on blood collected into tubes containing potassium
EDTA anti-coagulant:
Hemoglobin (Hb)
Erythrocyte count (RBC)
Hematocrit (Hct)
Erythrocyte indices - mean corpuscular hemoglobin (MCH)
- mean corpuscular volume (MCV)
- mean corpuscular hemoglobin concentration (MCHC)
Total leukocyte count (WBC)
Differential leukocyte count - neutrophils (Neut)
- lymphocytes (Lymph)
- monocytes (Mono)
- eosinophils (Eos)
- basophils (Bas)
Platelet count (PLT)
Reticulocyte count (Retic)
Prothrombin time (CT) was assessed by ‘Innovin’ and Activated partial thromboplastin time
(APTT) was assessed by ‘Actin FS’ using samples collected into sodium citrate solution (0.11
mol/L).

Blood Chemistry
The following parameters were measured on plasma from blood collected into tubes
containing lithium heparin anti-coagulant:
Urea
Inorganic phosphorus (P)
Glucose
Aspartate aminotransferase (ASAT)
Total protein (Tot.Prot.)
Alanine aminotransferase (ALAT)
Albumin
Alkaline phosphatase (AP)
Albumin/Globulin (A/G) ratio (by calculation)
Creatinine (Creat)
Sodium (Na+)
Total cholesterol (Chol)
Potassium (K+)
Total bilirubin (Bili)
Chloride (Cl-)
Bile acids
Calcium (Ca++)

Sacrifice and pathology:

3.5.1 Necropsy
Adult males were killed by intravenous overdose of suitable barbiturate agent followed by
exsanguination on Day 44 or 45. Adult females were killed by intravenous overdose of
suitable barbiturate agent followed by exsanguination on Day 14 post partum. Surviving
offspring were terminated by carbon dioxide asphyxiation followed by cervical dislocation on
Day 13 post partum. Offspring required for blood sampling were terminated by cervical dislocation
with death confirmed by decapitation during the sampling procedure with blood
samples collected immediately following decapitation. Any females which failed to achieve
pregnancy or produce a litter were killed around the same time as littering females.
For all females, the uterus was examined for signs of implantation and the number of uterine
implantations in each horn was recorded. This procedure was enhanced; as necessary, by
staining the uteri with a 0.5% ammonium polysulphide solution (Salewski 1964).
All adult animals and offspring, including those dying during the study, were subjected to a
full external and internal examination, and any macroscopic abnormalities were recorded.
Examination of offspring was restricted to a macroscopic external examination except where
abnormalities were observed, then an additional internal examination was performed.

Organ Weights
The following organs were dissected free from fat and weighed before fixation from five
selected males and five selected females from each dose group. Tissues with asterisk were
weighed from all remaining animals:
Adrenals
Prostate*
Brain
Seminal Vesicles (with coagulating gland)*
Epididymides*
Spleen
Heart
Testes
Kidneys
Thymus
Liver
Thyroid (weighed partially fixed with Parathyroid)*
Ovaries*
Uterus (weighed with Cervix)*
Pituitary (weighed partially fixed)*

Other examinations:

Thyroid Hormone Analysis
Blood samples taken to produce serum were allowed to clot, centrifuged and the serum from
each blood sample stored frozen at lower than -60ºC. Samples were taken as follows:
Where possible serum samples were taken from two randomly allocated offspring from each
litter on Day 4 post partum (if offspring were of the same sex, samples from the same litter
were pooled). If eight or fewer offspring were present in a litter, then no offspring from that
litter were sampled on Day 4 post partum.
Where possible, serum samples were taken from two randomly allocated offspring per litter
(one male and one female) on Day 13 post partum for T4 analysis. Where possible, a second
serum sample was also taken from two randomly allocated offspring per litter (one male and
one female) on Day 13 post partum for TSH analysis if required. If required the number/sex
of offspring sampled was altered depending on the litter constituents.
Two serum samples were taken from all adult males and females at termination. One serum
sample was for T4 analysis and the second sample was for TSH analysis if required.
All serum samples for Thyroxine (T4) analysis were dispatched to the Test Site (Envigo CRS
Limited, Woolley Road, Alconbury, Huntingdon, Cambridgeshire, PE28 4HS) where the
serum from adult males and Day 13 offspring was analyzed under the supervision of the
Principal Investigator (H Bose). A complete Thyroid Hormone Analysis report is presented
in Annex 3. All serum samples that were designated for TSH analysis were retained at the
Test Facility.

Statistics:

See below

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Incidences of increased salivation and noisy respiration were evident in animals of either sex
treated with 750 and 200 mg/kg bw/day throughout the treatment period and noisy respiration
was also evident in animals of either sex treated with 50 mg/kg bw/day albeit to a lesser
extent.

Mortality:

no mortality observed

Description (incidence):

There were no unscheduled deaths.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Males treated with 750 mg/kg bw/day showed a reduction in body weight gain during
Weeks 1, 3, 5 and 6 of treatment. No such effects were detected in males treated with 200 or
50 mg/kg bw/day.
No adverse effect in body weight development was evident in treated females during
maturation, gestation or lactation.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Males treated with 750 mg/kg bw/day showed a reduction in overall food consumption.
Females from this treatment also showed a reduction in food consumption during maturation.
No such effects were evident in animals of either sex treated with 200 or 50 mg/kg bw/day.
No effect on food conversion efficiency was evident in treated males or in treated females
during maturation.

Food efficiency:

no effects observed

Description (incidence and severity):

No effect on food conversion efficiency was evident in treated males or in treated females
during maturation.

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

no effects observed

Description (incidence and severity):

Visual inspection of water bottles did not reveal any inter-group differences.

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

There were no toxicologically significant effects detected in the hematological parameters measured. See below for details

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Males treated with 750 mg/kg bw/day showed increases in cholesterol, alanine
aminotransferase and albumin/globulin ratio and a reduction in total protein. No such effects
were evident in females treated with 750 mg/kg bw/day or in animals of either sex treated
with 200 or 50 mg/kg bw/day.

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

Behavioral Assessment
There were no toxicologically significant changes in the behavioral parameters measured.
Functional Performance Tests
There were no toxicologically significant changes in functional performance.
Sensory Reactivity Assessments
There were no treatment-related changes in sensory reactivity.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Males treated with 750 and 200 mg/kg bw/day showed an increase in liver weight both
absolute and relative to terminal body weight. No such effects were evident in treated
females or in males treated with 50 mg/kg bw/day.

Gross pathological findings:

no effects observed

Description (incidence and severity):

Macroscopic necropsy findings did not indicate any effect of treatment for either sex at
dosages of 50, 200 or 750 mg/kg bw/day.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The following treatment-related microscopic abnormalities were detected:
Liver: Centrilobular eosinophilia was present in four females treated with 750 mg/kg bw/day.
Centrilobular necrosis was present in two females and centrilobular vacuolation was present
in one other female treated with 750 mg/kg bw/day.
Increased rarefaction in the centrilobular region was present in two males treated with
200 mg/kg bw/day and in all males treated with 750 mg/kg bw/day.
No changes related to treatment were present in the liver of any males or females treated with
50 or females treated with 200 mg/kg bw/day.

Histopathological findings: neoplastic:

not examined

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

ca. 200 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

histopathology: non-neoplastic

2

Dose descriptor:

NOEL

Effect level:

ca. 200 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

female

Basis for effect level:

histopathology: non-neoplastic

3

Dose descriptor:

NOEL

Effect level:

ca. 50 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

Target system / organ toxicity

Critical effects observed:

no

Lowest effective dose / conc.:

750 mg/kg bw/day (actual dose received)

System:

hepatobiliary

Organ:

liver

Any other information on results incl. tables

Clinical Observations

Animals of either sex treated with 750 mg/kg bw/day showed incidences of increased

salivation from Day 3 (females) and Day 9 (males) onwards. Three males treated with 200

mg/kg bw/day also showed incidences of increased salivation between Days 31 and 37 and

one female treated with 200 mg/kg bw/day showed an isolated instance on Day 51. Instances

of noisy respiration were evident in the majority of animals of either sex treated with 750 and

200 mg/kg bw/day from Day 1 (males) and Day 2 (females) onwards and in four males and

six females treated with 50 mg/kg bw/day from Day 1 (males) and Day 22 (females)

onwards. Observations such as increased salivation and noisy respiration are commonly

observed following the oral administration of an unpalatable or irritant test item formulation

and represent difficulties in dosing particular animals rather than evidence of true systemic

toxicity.

Incidental observations, unrelated to test item administration, included noisy respiration in

three control males on one occasion only, an open wound and then scab formation in one

male treated with 50 mg/kg bw/day, vocalization in one female treated with 50 mg/kg bw/day

on one occasion only, generalized fur loss in one female treated with 200 mg/kg bw/day and

pilo-erection and hunched posture in one female treated with 750 mg/kg bw/day on one

occasion only.    

Functional Observations

Behavioral Assessments

There were no toxicologically significant changes in the behavioral parameters measured.

Isolated incidences of noisy respiration were evident in a small number of animals of either

sex from all treatment groups during the treatment period. These observations are likely to

reflect possible dosing difficulties on these occasions rather than true systemic toxicity and

correlate with the daily clinical observations recorded.

Functional Performance Tests

There were no toxicologically significant changes in functional performance.

Females treated with 750 mg/kg bw/day showed a statistically significant reduction (p<0.05)

in forelimb grip strength, however, the effect was confined to one out of the three tests.

Females from all treatment groups also showed a statistically significant reduction (p<0.05)

in the final 20% of activity. In the absence of a true dose related response, any similar effects

in males or any clinical signs of neurotoxicity, the intergroup differences were considered not

to be toxicologically significant.

Sensory Reactivity Assessments

Intergroup differences observed in the scores for sensory reactivity did not indicate any effect

of treatment for either sex at 50, 200 or 750 mg/kg bw/day.

Body Weight

Males treated with 750 mg/kg bw/day showed a reduction in body weight gain during Weeks

1 and 3 of treatment.  Body weight gain for these males was comparable to controls during

Weeks 2 and 4; however, body weight gain was again reduced during Weeks 5 and 6 of

treatment.  Statistical significance (p<0.01) was achieved for these males during Weeks 3 and

5.  Overall body weight gain for males treated with 750 mg/kg bw/day was 27% lower than

controls.  

No adverse effects were evident in males treated with 200 or 50 mg/kg bw/day.

A statistically significant reduction (p<0.01) in body weight gain was evident in males treated

with 200 and 50 mg/kg bw/day during Week 5, however, body weight gain prior to and after

this week was comparable to controls and no effect was evident on overall body weight gain.

The intergroup difference was therefore considered of no toxicological significance.  

No adverse effect in body weight development was evident in treated females during

maturation, gestation or lactation.  

Females treated with 750 and 200 mg/kg bw/day showed statistically significant increases

(p<0.05) in body weight gain during the first week of treatment and subsequently, higher

overall body weight gain during maturation was evident in these females.  An increase in

body weight gain is considered not to represent an adverse effect of treatment.  

Females treated with 750 mg/kg bw/day showed a statistically significant reduction (p<0.05)

in body weight gain during the first week of gestation.  Body weights for these females on

Day 0 and Day 7 of gestation were actually higher than control females, therefore, a lower

body weight gain during this period is not unexpected and is considered not to be of

toxicological significance.  Females treated with 750 mg/kg bw/day also showed a

statistically significant reduction (p<0.01) in body weight gain during the final week of

lactation.  Body weight gain for these females throughout gestation and lactation were within

historical control ranges and no effect on body weight was evident.  Body weight gain for

these females during the first week of lactation also exceeded control females, therefore, the

intergroup difference was considered not to be of toxicological significance.

Food Consumption

Males treated with 750 mg/kg bw/day showed a reduction (7%) in overall food consumption,

with the reduction being most significant during Weeks 1, 2, 4 and 6.  Females from this

treatment group also showed a reduction (13%) in food consumption during maturation.  

No such effects were evident in animals of either sex treated with 200 or 50 mg/kg bw/day.

No effect on food conversion efficiency was evident in treated males or in treated females

during maturation.

Females treated with 750 mg/kg bw/day showed a statistically significant reduction (p<0.05)

in food consumption during the second Week of gestation.  Individual values were within

historical control ranges and no effect was evident in the first or final week of gestation.  The

intergroup difference was therefore considered not to be of toxicological significance.  

Water Consumption

There was no effect of treatment on water consumption for either sex at 50, 200 or 750 mg/kg

bw/day; daily visual inspection of water bottles revealed no overt intergroup differences.

Hematology

There were no toxicologically significant changes in the hematological parameters examined.

Males treated with 750 mg/kg bw/day showed statistically significant reductions in

erythrocyte count (p<0.01), hematocrit (p<0.05), neutrophils (p<0.01) and eosinophils

(p<0.01).  With the exception of two individual values for erythrocyes and hematocrit, all

remaining individual values for these parameters were within the historical control ranges.  

Two control values for neutrophils and four control values for eosinophils were actually

above the historical control ranges.  In the absence of any associated histopathological

correlates the intergroup differences were considered not to be of toxicological significance.

Males from all treatment groups showed statistically significant reductions (p<0.05-0.01) in

total leukocyte count and lymphocytes.  With the exception of one individual value for both

parameters, all remaining individual values were within the historical control ranges and one

control value for lymphocytes and two control values for total leukocyte count were above

the historical control ranges.  A true dose related response was not observed for either

parameter, and in the absence of any associated histopathological correlates, the intergroup

differences were considered not to be of toxicological significance.    

Females treated with 750 mg/kg bw/day showed statistically significant reductions in mean

corpuscular hemoglobin, mean corpuscular volume and platelet count.  All of the individual

values for mean corpuscular hemoglobin and mean corpuscular volume were within the

historical control ranges, however, three individual values for platelet count were below the

historical control range.  In the absence of any associated histopathological correlates, the

intergroup differences were considered not to be of toxicological significance.  

Females treated with 200 mg/kg bw/day showed a statistically significant increase in mean

corpuscular hemoglobin concentration.  All of the individual values were within the historical

control range and in the absence of a similar effect at 750 mg/kg bw/day, the intergroup

difference was considered not to be of toxicological importance.  

Blood Chemistry

Males treated with 750 mg/kg bw/day showed statistically significant increases (p<0.05) in

cholesterol, alanine aminotransferase and albumin/globulin ratio and a statistically significant

reduction (p<0.05) in total protein.

No such effects were evident in females treated with 750 mg/kg bw/day or in animals of

either sex treated with 200 or 50 mg/kg bw/day.

Males from all treatment groups showed statistically significant reductions (p<0.05-0.01) in

alkaline phosphatase and bile acids.  With the exception of one individual alkaline

phosphatase value at 750 and 200 mg/kg bw/day, all remaining values were within the

historical control ranges and therefore were considered not to be of toxicological importance.

Males treated with 750 and 200 mg/kg bw/day also showed a statistically significant increase

(p<0.05) in potassium concentration and a statistically significant reduction (p<0.05) in

calcium concentration.  The majority of individual values were within the historical control

ranges and in the absence of a true dose related response, the intergroup differences were

considered not to be of toxicological importance.

Females treated with 750 and 200 mg/kg bw/day showed a statistically significant reduction

in bile acids.  Females treated with 750 mg/kg bw/day also showed statistically significant

increases (p<0.05-0.01) in albumin and albumin/globulin ratio.  All of the individual values

were within the historical control ranges, therefore, the intergroup differences were

considered not to be of toxicological importance.        

Necropsy

Macroscopic necropsy findings did not indicate any effect of treatment for either sex at

dosages of 50, 200 or 750 mg/kg bw/day.

The following macroscopic abnormalities were detected, however, they were either present in

the control group or were not associated with any treatment-related microscopic findings in

the treated groups and therefore were considered to be incidental.  Small testes in one control

male, small right seminal vesicle in one male treated with 750 mg/kg bw/day, an enlarged

cecum in one female treated with 750 mg/kg bw/day and a mass on the left ovary in one

female treated with 750 mg/kg bw/day.

Thyroid Hormone Analysis

Evaluation of Thyroxine (T4) in adult males and offspring at Day 13 of age did not identify

any obvious effect of treatment or indication of endocrine disruption at 50, 200 or 750 mg/kg

bw/day. Statistical analysis of the data did not reveal any significant intergroup differences.

Organ Weights

Males treated with 750 and 200 mg/kg bw/day showed a statistically significant increase

(p<0.05-0.01) in liver weight both absolute and relative to terminal body weight.  

No such effects were evident in treated females or in males treated with 50 mg/kg bw/day.

Males treated with 750 and 200 mg/kg bw/day showed statistically significant increases

(p<0.05) in brain, kidneys and testes weight both absolute and relative to terminal body

weight.  The majority of individual values were within the historical control ranges and in the

absence of true dose related responses or any associated histopathological correlates, the

intergroup differences were considered not to be of toxicological importance.  

Histopathology

The following treatment-related microscopic abnormalities were detected:

Liver: Centrilobular eosinophilia was present in four females treated with 750 mg/kg bw/day.

Centrilobular necrosis was present in two females and centrilobular vacuolation was present

in one other female treated with 750 mg/kg bw/day.

Increased rarefaction in the centrilobular region was present in two males treated with 200

mg/kg bw/day and in all males treated with 750 mg/kg bw/day.

No changes related to treatment were present in the liver of any males or females treated with

50 mg/kg bw/day or females treated with 200 mg/kg bw/day.

There were no test item-related microscopic findings in the reproductive tracts following the

qualitative examination of the stages of spermatogenesis in the testes (no test item-related

abnormalities in the integrity of the various cell types present within the different stages of

the sperm cycle) or the evaluation of the uterus or of follicles and corpora lutea in the ovaries.

Applicant's summary and conclusion

Conclusions:

The oral administration of Ceftazidime dihydrochloride to rats by gavage, at dose levels of
50, 200 and 750 mg/kg bw/day, resulted in reduced body weight gains in males treated with
750 mg/kg bw/day and microscopic liver changes in animals of either sex treated with
750 mg/kg bw/day and in males treated with 200 mg/kg bw/day. The ‘No Observed Effect
Level’ (NOEL) for systemic toxicity was therefore considered to be 200 mg/kg bw/day for
females and 50 mg/kg bw/day for males.
The increased cytoplasmic rarefaction in the liver of males was most likely due to variation in
glycogen storage within the cells and is generally considered to be an adaptive response,
therefore, a No Observed Adverse Effect Level (NOAEL) for males was considered to be
200 mg/kg bw/day.