FLUMEQUINE
First draft prepared by
Dr L. Ritter
Canadian Network of Toxicology Centres
University of Guelph, Guelph, Ontario, Canada
1. EXPLANATION
Flumequine is a first generation quinolone with anti-microbial
activity against gram negative organisms and is used for the treatment
of infections in animals. Flumequine had not been previously reviewed
by the Committee.
2. BIOLOGICAL DATA
2.1 Biochemical aspects
2.1.1 Absorption, distribution and excretion
Studies with 14C-flumequine in dogs and rats indicated that
flumequine is readily absorbed following oral administration. Peak
plasma levels occurred in male dogs between 2 and 4 hours after
dosing. Peak plasma levels were approximately 55-65 µg flumequine
equivalents/ml of plasma after an oral dose of 25 mg/kg bw.
Approximately one-half the concentration of total radioactivity for
the first 12 hours following administration corresponded to unchanged
drug. The disappearance of flumequine from the plasma appeared to
follow multi-exponential kinetics with an initial half-life of about
75 minutes and a terminal ß-phase half-life of 6.5 hours.
In rats, peak plasma levels of about 70 µg/ml were produced
approximately 2 hours after administration of the 25 mg/kg bw oral
dose. Most of the radioactivity in plasma appeared to be unchanged
drug. The plasma half-life for flumequine was 5.25 hours.
Total recovery of the orally administered dose was achieved in
the urine and faeces within 5 days after dosing in both species,
indicating that very little residual flumequine and/or metabolites
were retained in the tissues.
There was a significant difference in the mode of drug excretion
between dogs and rats. In dogs, 55-75% of the dose was excreted in the
faeces compared to only 10-15% in rats. Less than 5% of the dose was
present in the urine of dogs as unchanged drug while another 13-15%
was excreted as a conjugate of flumequine. In rats, 20-36% of the dose
was excreted in urine as unchanged drug and very little as a conjugate
of flumequine. The concentrations of free flumequine in the 24-hour
urine sample were about the same for both species.
The concentrations of flumequine in the plasma and urine of dogs
and monkeys during short-term toxicity studies were found to be
consistent with findings in these studies (Riker Research Laboratories
Inc., 1972a).
2.1.2 Biotransformation
In dogs, less than 5% of the dose was excreted in the urine as
unchanged drug and 13-15% was excreted as an acid-labile urinary
conjugate of flumequine (or a material fluorometrically similar to
flumequine). In rats, 20-36% was excreted in the urine as unchanged
drug and very little as an acid-labile conjugate (Riker Research
Laboratories Inc., 1972b).
Pre-treatment of rats with 100 mg flumequine/kg bw for 14 days
significantly reduced the duration of hexobarbital sleep time. This
indicates that treatment wth flumequine can increase liver microsomal
drug-metabolizing activity in this species under these experimental
conditions (Riker Research Laboratories Inc., 1972b).
2.2. Toxicological studies
2.2.1 Acute toxicity studies
The results of acute toxicity studies with flumequine are
summarized in Table 1.
2.2.2 Short-term toxicity studies
2.2.2.1 Mice
Flumequine was administered by gastric tube to 10 female Simonsen
Swiss Webster mice at 500 mg/kg bw/day for 14 days. Observations were
made daily with special attention directed to the occurrence of
alopecia. No signs of alopecia or other toxicity were noted (Riker
Research Laboratories Inc., 1972b).
2.2.2.2 Rats
Groups of 5 Simonsen Swiss Sprague-Dawley rats/sex/dose were
orally administered (by gastric tube) 0, 125, 250, or 500 mg
flumequine/kg bw/day for 14 days. No mortality occurred in the course
of the study. Marked alopecia was observed in both sexes of the
high-dose group after 3 to 5 days treatment, which persisted for the
duration of the study (Riker Research Laboratories Inc., 1972b).
Two groups of 5 Charles River CD rats/sex/dose and two groups of
5 Carworth Farms CFN rats/sex/dose were orally administered (by
gastric tube) 0 or 800 mg flumequine/kg bw/day for 14 days.
Observations were made daily for signs of toxicity and mortality.
Individual body weights were recorded daily. Clinical signs observed
in treated rats included bloating, cyanosis, dehydration, reduced
weight gain, and shedding. At necropsy, the only gross lesion reported
for the treated Charles River CD rats was alopecia over the left flank
area observed in one male. One male and 1 female Carworth Farms CFN
rats receiving flumequine died during the study. Urine stained
abdomen, red intestinal contents and meningeal haemorrhage were
reported in the male which died on day 12. No gross lesions were seen
in the female, which died on day 14. Gross lesions in the remaining
Carworth Farms CFN rats treated for 14 days with flumequine included
cachexia and paraphimosis in 1 male and urine stained abdomen in 1
female (Wazeter et al., 1971b).
Table 1. Acute toxicity studies1
Species Sex Route LD50 (mg/kg bw)
Mouse F oral 2480 (2000-3075)
F oral (fasted) 1630 (1190-2233)
F i.v. 97 (90-104)
F i.v. 90 (86-93)
F i.v. 822 (718-944)
Rat M oral (fasted) 2210 (1864-2625)
F oral (fasted) 2450 (1992-3014)
F oral (fasted) 1340 (971-1849)
F oral (fasted) 1375 (1170-1620)
F oral (fasted) 1753 (1520-2025)
Rabbit M oral > 2000
Dog 2 i.v. > 120
1 Riker Reserach Laboratories, 1972b.
2 In this particular study, the test compound was administered
as a 2% solution for two days per dose level; one male and one
female each received 100 or 120 mg/kg bw, respectively.
Although severe clonic-tonic convulsions, prostration,
urination and defection were seen in all test animals, all
dogs had returned to normal by the second day and were free of
signs of toxicity for the balance of the fourteen-day
observation period.
Groups of 10 Charles River Sprague-Dawley rats/sex/dose were
orally administered (by gastric tube) 0, 200, 400, or 800 mg
flumequine/kg bw/day for 90 days. Observations were made daily for
signs of toxicity and body weights were recorded weekly.
No mortalities were reported. Body-weight gain was signif-icantly
depressed in both sexes of the mid- and high-dose groups. Alopecia
occurred in all treated rats, which appeared to be more severe in
females than in males. Sporadic urinary incontinence occurred in most
rats of the high-dose group and in a few females of the low-dose
group. Salivation was noted in all rats of the mid- and high-dose
groups, which was not reported in the low-dose or control groups.
Pilomotor erection was seen sporadically in rats of the control, mid-,
and high-dose groups.
Haematological and clinical chemistry data revealed no
treatment-related effects. However, urine of all treated rats showed
a dose-related positive acetone (ketone) reaction. The authors
suggested that this effect could have been due to the interference of
the ketone test by the presence of flumequine metabolites in the
urine.
Relative kidney weights in both sexes and absolute kidney weights
in males were increased significantly at the high-dose. The relative
adrenal weights were significantly increased in both sexes at the mid
and high doses. Relative weights of heart, brain, spleen and testes
were also significantly increased in males of the high-dose group.
Information on the microscopic examination of these organs was not
available.
Alopecia was the only gross abnormality observed at necropsy. A
dose-related significant increase in relative liver weights occurred
in all treated rats. Microscopic examination of liver revealed swollen
and enlarged hepatocytes (30 to 90%) in rats of the high-dose group.
Similar degenerative changes in hepatocytes were not observed in rats
at the mid and low doses. The authors suggested that enlargement of
the liver was due to stimulation of drug metabolizing enzymes by
flumequine. A NOEL could not be determined in this study (Nelson et
al., 1972a).
2.2.2.3 Guinea-pigs
Groups of 5 female Hartley strain guinea-pigs were given oral
doses of 0, 300, or 500 mg flumequine/kg bw/day by gavage for 14 days.
Hair samples were plucked at initiation and termination of the study
to examine any differences in hair growth patterns. Mortality was
noted after 4 days in the high-dose group (2/5) with the remaining 3
animals dying after 6 days. Two animals in the low-dose group died,
one at day 12 and other one day after cessation of treatment. No
alopecia was noted at any time during the study. No changes were seen
microscopically in the hair samples taken at termination when compared
with those taken at initiation of the study. Information on necropsy
was not available (Riker Research Laboratories Inc., 1972b).
2.2.2.4 Dogs - 90 Days
Flumequine was given orally by gelatin capsule at 150 mg/kg bw
twice daily for 21 days to 2 mongrel dogs, one male (8.3 kg) and 1
female (5.0 kg). Prominent signs noted within 3 hours of
administration included emesis, depression, ataxia, and mild
hyperactivity. These signs were most severe between the 10th and 14th
days after which they appeared to diminish. Both dogs became anorectic
after the first week and, as a result, the male lost 0.6 kg and the
female 0.8 kg during the study. No gross lesions were observed at
necropsy in either dog (Riker Research Laboratories Inc., 1972b).
Flumequine was administered orally (by gelatin capsule or tablet)
to four groups (2/sex/group) of young adult purebred beagle dogs.
Dosages administered were 0, 25, 50, or 100 mg flumequine/kg bw given
twice daily for 90 days. Each dog was observed for signs of toxicity
immediately following dosing and periodically throughout the day. Body
weights were recorded at weekly intervals.
There were no mortalities or consistent signs of toxicity at any
dosage level. Flushing of the skin was the only clinical sign seen in
treated dogs. This occurred very infrequently and in no specific
pattern. Only minor fluctuations in body weight were observed during
the study. None of the changes were considered significant or
treatment-related.
Haematologic and urinary parameters appeared to be unaffected by
the administration of flumequine. Elevation of LDH values occurred in
dogs at the low (1/4), mid (1/4), and high (3/4) doses on day 14. LDH
values were normal on subsequent evaluations at days 42 and 90.
Gross and microscopic examination of heart, liver, kidney and
skeletal muscle at the end of the study revealed no treatment-related
changes (Nelson et al., 1972b).
2.2.2.5 Dogs - 1 year
Groups of four male and four female beagle dogs were given total
daily oral doses of 0, 50, 100, or 200 mg flumequine/kg bw/day divided
in half as twice daily doses. Emesis in the high-dose group resulted
in this group receiving only a single 100 mg/kg bw dose for the first
five days, after which the emesis subsided and the scheduled dosing of
200 mg/kg/bw day divided into two 100 mg/kg bw doses was resumed.
All dogs survived the one-year treatment period. A decrease in
food consumption was noted in all treatment groups throughout the
study. Declines in food consumption were reflected in weight loss over
the first three weeks of the study. Weight loss did not appear to be
entirely dose-dependent but due to the somewhat random distribution of
affected animals within dose groups.
A dose-dependent incidence of convulsive episodes was observed in
treated dogs. The convulsions were relatively severe, of short
duration (15-30 seconds), and almost always followed by ataxia and
tremors. Normal behaviour returned within about ten minutes after
treatment. Other drug-related clinical signs observed included ataxia,
hypoactivity, tremors, emesis (particularly early in the study),
decreased food consumption, and body-weight loss. Less frequently
observed treatment-related clinical signs included excessive
salivation and mild gingivitis in five of eight high-dose dogs and in
one mid-dose dog during the last six months of the study.
Drug-related effects noted on physical examination included
ataxia, a slow-knuckling response, and exaggerated knee and toe
reflexes in one animal. Other effects appeared to be somewhat random,
occurring in both control and treated animals.
Treatment-related effects were not observed in haematology, serum
chemistry, and urinalyses, organ weight data, or gross and microscopic
pathology. The NOEL for this study was 50 mg/kg bw/day (Saunders &
Case, 1976).
2.2.2.6 Monkeys
Flumequine was given orally by gelatin capsule twice daily at
increasing dosage levels for 15.5 weeks to 3 female rhesus monkeys as
follows: 100 mg/kg bw/day for 1 week, 200 mg/kg bw/day for 3 weeks,
300 mg/kg bw/day for 8 weeks, 400 mg/kg bw/day for 1 week, 500 mg/kg
bw/day for 1 week, and 600 mg/kg bw/day for 1.5 weeks. One monkey died
accidentally on day 2 of drug administration. Clinical signs noted
during the study included emesis, total anorexia, and transient hair
loss. No gross lesions were observed at necropsy in either monkey. No
microscopic abnormalities were noted in skin sections. Although
specimens of the organ tissues were collected for microscopic
examination, no further information was provided (Wazeter, et al.,
1971a).
2.2.3 Long-term toxicity/carcinogenicity studies
2.2.3.1 Mice
In an 18-month study, flumequine was administered in the feed
(concentrations not stated) to provide doses of 0, 400, or 800 mg/kg
bw/day to groups of 93 Charles River CD-1/ ICR mice of each sex. The
mice were observed daily for clinical signs of toxicity. Food
consumption and body weights were recorded periodically. At the end of
the study, animals were necropsied and subjected to a complete gross
examination. Microscopic examination was conducted on tissues and
gross lesions from all animals.
A slight depression in body weight occurred in the high-dose
group from the sixth week to termination of the study. There were no
differences in food consumption in male or female mice of the treated
and control groups throughout the study. Survival rates were
comparable in treated and control groups. Clinical observations showed
no adverse effects attributable to the administration of flumequine.
Information was not available on haematology, clinical chemistry,
urinalysis, or organ weights.
Incidences of liver tumours seen grossly at necropsy, which are
summarized in Table 2, were dose-related and more prevalent in males
than in females.
The liver tumours were classified histologically into hepatoma,
hepatoma with atypica, and hepatocellular carcinoma. The first two,
hepatoma and hepatoma with atypica, were considered benign, and
hepatocellular carcinoma was considered malignant in this study. A
definite dose-response was apparent and the higher incidence of both
benign and malignant liver tumours in males, observed grossly, was
confirmed by histopathological analysis. Dose-related toxic changes in
hepatocytes occurred in the low-dose males and in the high-dose males
and females. These included cytoplasmic degenerative changes,
vacuolation, fatty infiltration, and the presence of lymphocytes and
neutrophils. The incidence of hepatic toxic changes paralleled the
liver tumour incidence. Chi-square analysis of the number of
tumour-bearing animals indicated significant increases (p < 0.05) for
the low- and high-dose males considering all tumours and benign
tumours. The number of high-dose males with both benign and malignant
liver tumours was also statistically significant. In females, the only
significant increases occurred in the high-dose group for numbers of
animals with any type or benign only tumours. No other tissue changes
were considered significant or treatment-related. A NOEL could not be
determined in this study (Sibinski et al., 1977a).
A special 18-month dietary study of flumequine was conducted to
correlate the length of drug administration with the development of
toxic and neoplastic liver changes observed in the Sibinski et al.
(1977a) study. Five groups of male Charles River (CD-1/ICR) mice
comprised the study. The substance was administered via dietary
admixture. Group A (60 males) served as controls and received no
treatment. Group B (100) males received flumequine at 800 mg/kg bw/day
for 18 months; interim necropsies of 10 mice each were done at 3, 6,
9, and 12 months to follow the development of the liver tumorigenic
response. Group C (80) males received flumequine at 800 mg/kg bw/day
for the first 6 weeks of the study; for the next 6 weeks they were off
drug; the following 6 weeks they were back on the same dose of drug
and then off drug for the rest of the study. Necropsies of 10 mice
each were done at 12, 18, and 24 weeks. Group D (60) males received
flumequine at 800 mg/kg bw/day for the first 6 weeks of the study,
then fed control diet for the rest of the study. At the end of the
6-week period, 10 mice were necropsied. Group E (50) males received a
formulation of flumequine at 800 mg/kg bw/day that contained less
than 0.001% of dimethylformamide (DMF) for 18 months. Group E was
added to evaluate whether the 0.3% DMF present in the lot administered
in the previous 18-month study had a role in the carcinogenic
response. The analytical specification for DMF is < 0.5%. Interim
necropsies were performed on 5 mice after 6 weeks and on 10 mice after
12 months of drug treatment.
Table 2. Incidence of liver tumours and toxic changes in the liver in
18-month oral carcinogenicity study of flumequine in mice
Control Low dose High dose
(400 mg/kg bw/day) (800 mg/kg bw/day)
Males Females Males Females Males Females
Number of n=70a n=64a n=75a n=69a n=78a n=69a
mice with n n n n n n
liver tumours (%) (%) (%) (%) (%) (%)
Any type 6 0 28b 0 69b 9b
(9) (37) (88) (13)
Benign 6 0 25b 0 36b 7b
onlyc (9) (33) (46) (10)
Benign & 0 0 0 0 30b 0
malignantd (38)
Only 0 0 3 0 3 2
malignante (4) (4) (3)
---------------------------------------------------------------------------------------------
Toxic 0 32b 1 78b 39b
changes in (43) (100) (57)
liver
a Number of animals that had gross and microscopic tissue
examination.
b Significant difference from control (p <0.05) (Chi-square).
c Hepatoma and/or hepatoma with atypica.
d Hepatoma with or without atypica and hepatocellular carcinoma
in the same animal.
e Hepatocellular carcinoma.
The mice were observed daily for clinical signs of toxicity with
the exception of week-ends and holidays, during which only live/dead
checks were made. Daily observations were replaced with live/dead
checks during the last third of the study. For the first 18 weeks of
the study, body weights and food consumption were recorded weekly;
thereafter, they were recorded on a monthly basis. Liver tumours and
toxic changes in the liver were classified histologically as described
in the previous Sibinski et al. 1977a study.
Mice in Group B and Group E had lower mean body weights from
weeks 18 to 78 and higher mortality rates as compared to Group A
controls. Group E showed a 15% higher food intake from week 18 to
termination. Incidence of swollen abdomen was more prevalent in the
treated groups than in the control group. Information was not
available on haematology, clinical chemistry, urinalysis, or organ
weights.
Interim necropsies of Group B mice revealed a time-dependent
development of liver tumours following flumequine administration. At
3 months, 0/10 mice had liver tumours, but all 10 mice had evidence of
toxic changes in the liver. The number of mice with liver tumours at
6, 9 and 12 months was 1/10, 3/10, and 9 (2 malignant)/ 10,
respectively. Interim necropsies of Group E mice at week 6 revealed
toxic changes in the liver of all 5 mice. At 12 months, 6/10 mice had
liver tumours.
Table 3 shows the incidence of liver tumours and toxic changes in
the liver of all mice necropsied at the end of the study. An increase
in the incidence of liver tumours, both benign and malignant, was
statistically significant for mice in Groups B and E. Two mice in
Group B had metastatic lung lesions of hepatocellular carcinoma
origin. A large percentage of mice in Group B (81%) and Group E (97%)
had toxic changes in the liver as compared to Group A controls (0%).
Toxic changes in the liver which were reversible and no longer
evident at the end of the study, as shown in Table 3, occurred in
Groups C and D. No liver tumours were found in animals killed for
interim necropsies. Although the percent of animals with any type of
liver tumour was increased nearly 2-fold compared to controls in
Groups C and D, the increase was not statistically significant.
Results from Group E indicated that the presence of DMF as a
contaminant in flumequine did not influence the development of toxic
and neoplastic liver changes in mice in response to oral flumequine
exposure (Sibinski et al., 1979).
2.2.3.2 Rats
Groups of 60 Carworth CFN (Wistar derived) rats/sex/dose were
orally administered flumequine via dietary admixture (concentrations
nolt stated), to provide daily doses of 0, 200, 400, or 800 mg
flumequine/kg bw/day. The rats were observed daily for clinical signs
of toxicity. Food consumption and body weights were recorded
periodically. At the end of the study, animals were necropsied and
subjected to complete gross examinations. Microscopic examinations
were conducted on the tissues and gross lesions from all animals.
Table 3. Incidence of liver tumours and toxic changes in the liver at the
end of the special 18-month toxicity study of flumequine in male
mice
Group A Group B Group C Group D Group E
Number of n=60a n=58a n=49a n=48a n=35a
mice with n n n n n
liver tumours (%) (%) (%) (%) (%)
Any type 7 39b 11 10 29b
(12) (67) (22) (21) (83)
Benign onlyc 5 26b 8 7 15b
(8) (45) (16) (15) (43)
Benign & 1 12b 2 1 11b
malignantd (2) (21) (4) (2) (31)
Malignant 1 1 1 2 3
onlye (2) (2) (2) (4) (9)
--------------------------------------------------------------------------------
Toxic 0 47b 0 0 34b
changes in liver (81) (97)
a Number of animals that had gross and microscopic examination.
b Significant difference from control (p <0.05) (Chi-square).
c Hepatoma and/or hepatoma with atypica.
d Hepatoma with or without atypica and hepatocellular carcinoma
in the same animal.
e Hepatocellular carcinoma.
Dose-related decreases in mean body weight and food consumption
occurred in rats of flumequine treated groups. Mortality at 400 and
800 mg/kg bw/day was significantly reduced. Results of haematology,
clinical chemistry, and urinalysis were comparable in treated and
control groups.
Significant increases in the mean relative weights of the
pituitary gland, liver, heart, and brain occurred in males in the mid-
and high-dose groups. A similar effect was observed in the mean organ
weights of the liver, heart, and brain of females in the high-dose
group.
Microscopically, benign chromophobe adenoma was noted in the
pituitary gland of males at the mid- and the high-doses, but the
incidence was not greater than in controls. Livers showed scattered
foci of swollen hepatocytes due to mild degenerative changes. A few of
these cells also had fatty changes with fat droplets in their
cytoplasm. Spermatogenesis was absent in many of the males at the mid
and high doses; this effect was not analyzed statistically.
No carcinogenic effect attributable to flumequine was observed
either during or at the end of 2 years of its administration. The
benign and malignant tumours observed in all groups were considered
spontaneous in nature and there was no significant increase in tumour
incidence in treated groups as compared to controls. The NOEL was 200
mg/kg bw/day (Sibinski et al., 1977b).
2.2.4 Reproduction studies
2.2.4.1 Rats
A fertility and general reproductive performance (Segment I)
study with flumequine was conducted in Charles River Sprague-Dawley
rats. Groups of 11 or 12 males weighing 140-160 g were treated, by
gavage, with doses of 0, 100, 200, 400, or 800 mg flumequine/kg bw/day
for at least 80 days before breeding and throughout the breeding
period. Females weighing 150-215 g were treated with a gavage dose of
flumequine for at least 21 days prior to breeding and throughout
gestation and lactation. The females were divided into 8 groups each
having 20 or 21 animals. Dose schedules varied by group as follows:
Group I Control
Group II 800 mg/kg bw/day (19/21 animals died in the
second week of treatment).
Group III 400 mg/kg bw/day until breeding, bred to males of
the 400 mg/kg bw/day group, then dosed at 200
mg/kg bw twice daily throughout gestation and
lactation.
Group IV 200 mg/kg bw/day until breeding, bred to males of
the 200 mg/kg bw/day group, then dosed at 100
mg/kg bw twice daily throughout gestation and
lactation.
Group V 100 mg/kg bw/day until breeding, bred to males of
the 200 mg/kg bw/day group, then dosed at 50
mg/kg bw twice daily throughout gestation and
lactation.
Group VI Control, bred to males of the 800 mg/kg bw/day
group.
Group VII 200 mg/kg bw/day, bred to males of the 400 mg/kg
bw/day group, dosing stopped on the 15th day of
gestation.
Group VIII 100 mg/kg bw/day, bred to males of the 200 mg/kg
bw/day group, dosing stopped on the 15th day of
gestation.
Group II females had 4 deaths in the first week and 15 deaths in
the second week of flumequine treatment. The mean body weight was
significantly lower than that of controls. Prominent signs of toxicity
included alopecia, prostration, and respiratory depression. The
remaining 2 females were sacrificed after 3 weeks of dosing. Necropsy
results were not available.
Group III females had significantly lower mean body weight,
longer mean gestation period, smaller mean litter size, and a larger
number of dead pups than did the controls. Group IV females showed a
similar pattern of changes as Group III females in pregnancy rate,
length of gestation, litter size and pup survival, but the changes
were not statistically significant. The mean pup weights of Group III
and Group IV were significantly lower when compared to the controls.
No significant changes in reproduction parameters were noted with
females of Groups V, VI, VII and VIII. However, the pups from females
treated with flumequine (100, 200, or 400 mg/kg bw/day) throughout
gestation and lactation had significant lower mean body weight at
birth and at weaning. A NOEL could not be determined in this study
(Gortner & Case, 1974a).
2.2.5 Special studies on embryotoxicity/teratogenicity
2.2.5.1 Mice
Groups of 18 or 22 pregnant Charles River CD-1 mice were given
doses of 0, 50, 100, 200, or 400 mg flumequine/kg bw/day by gavage
from the sixth through fifteenth days of gestation. Observations were
made daily for signs of toxicity and body weights were recorded on
days 6, 9, 12, 15, and 17 of pregnancy. Ovaries, uteri, and their
contents were collected from animals at termination on day 17 to
determine the number of viable fetuses, number of resorption sites,
fetal weights, and gross fetal abnormalities.
Mean maternal body weights at 200 and 400 mg/kg bw/day were
significantly reduced from the twelfth day of gestation throughout the
rest of pregnancy. No change in the number of viable fetuses or
resorption sites was observed in any treatment group. A slight
reduction in mean fetal weight was noted at 400 mg/kg bw/day, but the
change was not significant when compared with the control value. Cleft
palate was seen grossly in 3% (6/227) of fetuses from the high-dose
group. Internal examination of 72 of the fetuses revealed that 9 (13%)
had cleft plate. Of these, 4 had been detected on gross examination.
There was one fetus each with cleft palate at the 50 and 100 mg/kg
bw/day level but none at the 200 mg/kg dose level. Incomplete
ossification of sternebra and skull bones were noted in the great
majority of the fetuses in all groups including the controls. The
authors suggested that the incomplete ossification was the result of
removing the fetuses one day earlier than the 18-day gestation period
known to be required for this strain of mice. The NOEL in this study
was 400 mg/kg bw/day (Gortner & Case, 1974b).
Groups of 32 or 35 pregnant OFI-IOPS mice were orally
administered (by gastric tube) doses of 0, 100, 200, or 400 mg
flumequine/kg bw/day from the second to fifteenth days of gestation.
Incomplete ossification, invaginated trachea, dilatation of the renal
pelvis, and cleft palate were observed in fetuses at the mid and high
doses. These observations were interpreted as evidence of fetotoxic,
not teratogenic, responses to exposure to flumequine. The NOEL in this
study was 100 mg/kg bw/day (Ecole Nationale Vétérinaire de Lyon,
1974).
2.2.5.2 Rats
Groups of 23 or 27 pregnant COBS rats were dosed orally (by
gavage) with 0, 100, 200, or 400 mg flumequine/kg bw/day from the
sixth through fifteenth days of gestation. Observations were made
daily for signs of toxicity and body weights were recorded on days 6,
9, 12, 15, and 20 of pregnancy. Ovaries, uteri and their contents were
collected from animals at termination on day 20 to determine the
number of corpora lutea, number of resorption sites, number of viable
fetuses, fetal weights and fetal abnormalities.
There was a dose-related reduction of mean body weight in the
treated dams and the difference from controls was significant at 400
mg/kg bw/day. The mean fetal weights of the mid- and high-dose groups
were significantly lower as compared to controls. Dose-related
incomplete ossification of sternebra, vertebrae, and skull bones were
also noted in fetuses of the mid- and high-dose groups. No
drug-related visceral or skeletal malformations were found and there
was no embryotoxic effect noted in this study. The NOEL in this study
was 100 mg/kg bw/day (Nelson & Owen, 1972a).
2.2.5.3 Rabbits
Groups of 15 or 21 pregnant New Zealand white rabbits were orally
administered (by gastric tube) doses of 0, 100, 200, or 400 mg
flumequine/kg bw/day from sixth through eighteenth days of gestation.
Observations were made daily for signs of toxicity and body weights
were recorded on days 0, 6, 14, 21, and 29 of pregnancy. On day 29 the
animals were killed and uterine disposition of young, resorption
sites, and number of corpora lutea were evaluated. Viable young were
weighed, sexed, and examined internally and externally for
abnormalities.
There was a slight, but not significant reduction of mean body
weights of dams and pups in the mid- and high-dose groups. Examination
of the stained skeletons of the pups revealed no increase of
incomplete ossification of bones in any dose group. No drug-related
visceral or skeletal teratologic changes, or embryotoxic effects were
noted in this study. The NOEL in this study was 400 mg/kg bw/day
(Nelson & Owen, 1972b).
2.2.6 Special studies on genotoxicity
The results of in vitro and in vivo genotoxicity studies of
flumequine are summarized in Table 4.
2.3 Observations in humans
No information was available.
Table 4. Results of genotoxicity studies on flumequine
Test Test object Concentration Results References
In vitro
Ames test (1) S. typhimurium 0.01-1000 negative Rohlfing &
TA1515, 1537, µg/disc Winandy, 1977
1538, 98, 100
HGPRT test (1) Mouse L5178Y 0-200 µg/ml negative Kennelly et al.,
lymphoma cells 1985
Gene mutation Chinese hamster 0-200 µg/ml negative Kirkland et al.,
assay (1) ovary cells 1985
In vivo
Chromosome Rat bone marrow 1000 mg/kg negative Marshall et al.,
aberration assay bw po 1987
(1) With and without rat liver S-9 fraction.
3. COMMENTS
Information from a range of studies on flumequine was available
for assessment, including data on pharmacokinetics, acute toxicity,
short-term and long-term toxicity, reproductive and developmental
toxicity, and genotoxicity.
Studies with 14C-labelled flumequine in dogs and rats indicated
that flumequine is readily absorbed following oral administration.
Most of the radioactivity in plasma appeared to be unchanged drug. The
plasma half-life for flumequine was 5.25 hours in the rat. There were
some differences in the pattern of drug excretion between dogs and
rats. In dogs, 55-75% of the dose was excreted in the faeces, while in
rats, only 10-15% was excreted by this route. Less than 5% of the dose
was present in the urine of dogs as unchanged drug and 13-15% as a
conjugate of flumequine. In rats, 20-36% was eliminated in urine as
unchanged drug and very little as a conjugate of flumequine.
Single oral doses of flumequine were slightly toxic (LD50 =
1630-2210 mg/kg bw) in rats, mice, and rabbits.
The most common findings in rats dosed with 800 mg/kg bw/day by
gastric tube for 14 days included bloating, cyanosis, dehydration,
reduced weight gain, and alopecia. In a 90-day study in rats, animals
receiving doses of 0, 200, 400, or 800 mg/kg bw/day by gastric
intubation showed a dose-dependent significant increase in relative
liver weights. Guinea-pigs were given repeated gavage administration
of 300 or 500 mg/kg bw/day for 14 days, and two of six animals died at
the 300 mg dose. All animals receiving 500 mg/kg bw/day died after six
days of treatment.
Repeated oral administration of flumequine to dogs at 300 mg/kg
bw/day for 21 days resulted in emesis, depression, ataxia, and mild
hyperactivity, but there was no mortality or consistent signs of
toxicity at 200 mg/kg bw given in divided doses. In a one-year study
in dogs given total daily oral doses up to 200 mg/kg bw/day, the most
prominent effects were neuro-logical signs. The NOEL was 50 mg/kg
bw/day.
In an 18-month carcinogenicity study in mice, flumequine was
administered in the feed at 0, 400, or 800 mg/kg bw/day. The only
clinical signs were a slight depression in body weight which occurred
in the high-dose group from the sixth week to termination of the
study. The incidence of benign and malignant liver tumours combined
was dose-related with 9, 37 and 88% in the control, low-dose, and
high-dose males affected, respectively, and 0, 0, and 13% in the
control, low-dose, and high-dose females affected, respectively.
Dose-related toxic changes in the hepatocytes, which paralleled the
liver tumour incidence, occurred in the low-dose males and in the
high-dose males and females. The incidence of hepatotoxicity was
statistically significant in both male treatment groups and in the
high-dose female group. A NOEL could not be determined in this study.
A further 18-month dietary study in mice of flumequine was
conducted to investigate the relationship of duration of drug
administration with the development of toxic and neoplastic liver
lesions. Interim necropsies of males receiving 800 mg/kg bw/day
revealed a time-dependent development of liver tumours following
flumequine administration. At 3 months, 0/10 mice had liver tumours,
but the same 10 mice all had evidence of toxic changes in the liver.
The number of mice with liver tumours at 6, 9, and 12 months was 1/10,
3/10, and 9/10, respectively. Of these, malignant tumours were
observed in two animals from the 12-month sacrifice. Tumours observed
in all other animals were benign.
In a two-year carcinogenicity study in rats dosed with flumequine
at 0, 200, 400, or 800 mg/kg bw/day, no carcinogenic effects were
observed. Dose-related decreases in mean body weight and food
consumption occurred. Spermatogenesis was absent in many males in the
mid- and high-dose groups, in addition to significant increases in the
mean relative weight of the pituitary gland, liver, heart, and brain.
A similar effect was observed in the mean weights of the liver, heart,
and brain of females in the high-dose group. At the high dose the
liver showed foci of swollen hepatocytes due to mild degenerative
changes and a few cells also had fatty changes. The NOEL was 200 mg/kg
bw/day.
There was evidence of compound-related tumorigenic effects in the
liver of mice. The Committee noted that the tumorigenic activity of
flumequine was most pronounced in the liver of male mice, which are
known to be sensitive to liver tumour induction. As the compound was
negative in a range of mutagenicity studies, the mechanism of this
tumorigenesis is unclear.
A fertility and general reproductive performance study on
flumequine was conducted in rats. In an unconventional protocol,
groups of male and female rats were treated with gavage doses of
flumequine at 0, 100, 200, 400, or 800 mg/kg bw/day. Virtually all
females in the high-dose group died within two weeks of initiation of
treatment. Because of reduced body weight of pups at all doses, a NOEL
could not be determined, but the Committee noted that there were no
effects on fertility or reproductive performance of the dams.
In a teratogenicity study, groups of mice were given gavage doses
of 0, 50, 100, 200, or 400 mg flumequine/kg bw/day from the sixth
through fifteenth days of gestation. Incomplete ossification of
sternebra and skull bones were noted in many of the fetuses in all
groups including the controls. The NOEL was 400 mg/kg bw/day in this
study.
In another teratogenicity study, groups of mice received doses of
0, 100, 200, or 400 mg flumequine/kg bw/day by gastric tube from the
second to fifteenth days of gestation. Increased frequency in cleft
palate was considered to be indicative of fetotoxicity and
compound-related in the mid- and high-dose groups. The NOEL was 100
mg/kg bw/day.
In a teratology study, groups of rats were dosed orally with 0,
100, 200, or 400 mg flumequine/kg bw/day from the sixth through
fifteenth days of gestation. There was a significant reduction of mean
body weight at 400 mg/kg bw/day. In the mid- and high-dose groups,
there was a significant reduction in mean fetal weights and incomplete
ossification of sternebra, vertebrae, and skull bones. No drug-related
visceral or skeletal malformation were observed and no embryotoxic
effects were observed in this study. The NOEL was 100 mg/kg bw/day.
In a rabbit teratology study, animals were dosed by gavage with
0, 100, 200, or 400 mg flumequine/kg bw/day from the sixth through
eighteenth days of gestation. No drug-related visceral or skeletal
teratogenic changes or embryotoxic effects were noted in this study.
The NOEL was 400 mg/kg bw/day.
The Committee recognized the association of quinolone exposure
and arthropathy and concluded that data to evaluate this hazard were
not adequate for flumequine.
Genotoxicity studies in an in vitro bacterial and mammalian
gene mutation assay and in an in vivo mammalian chromosome
aberration assay were negative.
No data were available that would permit the Committee to
evaluate the microbiological hazard of flumequine residues in food.
4. EVALUATION
The Committee was unable to establish an ADI for this compound
due to the absence of the information outlined below. Before reviewing
flumequine again the Committee would wish to see:
A. Further data from mice which would identify NOELs for
hepatotoxicity.
B. Information regarding the tumorigenic mechanism of
flumequine.
C. Further data relating to whether the compound induces
arthropathy.
D. Information regarding the microbiological safety of
flumequine residues.
E. Appropriate residue data.
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