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. 5. 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Study to determine the ability of MBR 10995 to induce mutations to 6-thioguanine resistance in mouse lymphoma L5178Y cells using a fluctuation test. Unpublished report from Microtest Research Ltd., Heslington, York, UK. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. KIRKLAND, D.J., GARNER, J.V., RUTTER, A., BIDGOOD, J. & ARNOLD, W. (1985). Study to evaluate the chromosome damaging potential of MBR-10995-R-802 (flumequine) by its effects on cultured Chinese hamster ovary (CHO) cells using an in vitro cytogenetics assay. Unpublished report from Microtest Research Ltd., Heslington, York, UK. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. MARSHALL, R.R., HULME, L., BIDGOOD, J., RUTTER, A., McENANEY, S., TAYLOR, M., FEASBY, T., BARKER, L., KENNELLY, J.C. & COLE, H. (1987). Study to evaluate the chromosome damaging potential of MBR 10995 (flumequine) by its effects on the bone marrow cells of treated rats. Unpublished report from Microtest Research Ltd., Heslington, York, UK. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. NELSON, R.A. & OWEN, G. (1972a). Effect of R-802 (flumequine) on pregnancy of the albino rat. Unpublished report from Riker Laboratories Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. NELSON, R.A. & OWEN, G. (1972b). Effect of R-802 (flumequine) on the pregnancy of the New Zealand white rabbit. Unpublished report from Riker Laboratories Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. NELSON, R.A., CASE, M.T. & HAMILTON, R.R. (1972a). Ninety (90) day subacute oral toxicity of flumequine in Charles River rats. Unpublished report from Riker Laboratories, Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. NELSON, R.A., CASE, M.T., GLICK, P.R., & STEFFEN, G.R. (1972b). Ninety (90) day subacute oral toxicity of flumequine in beagle dogs. Unpublished report from Riker Laboratories, Inc. St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. RIKER RESEARCH LABORATORIES (1972a). Metabolic studies of R-802 (flumequine). Unpublished report from Riker Research Laboratories Inc., St. Paul, MN, USA. Submitted by Sanofi Santé Nutrition Animale, Libourne Cedex, France. RIKER RESEARCH LABORATORIES (1972b). Range-finding studies of R-802 (flumequine) in mice, rats, guinea-pigs, and dogs. Unpublished report from Riker Research Laboratories Inc., St. Paul, MN, USA. Submitted by Sanofi Santé Nutrition Animale, Libourne Cedex, France. ROHLFING, S.R. & WINANDY, R.M. (1977). Mutagenicity study with MBR 10995 (flumequine). Unpublished report from Riker Laboratories, Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. SAUNDERS, D.R. & CASE, M.T. (1976). One-year oral toxicity study of R-802 in dogs. Unpublished report from Riker Laboratories, Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Codex, France. SIBINSKI, L.J., STEFFEN, G.R. & CASE, M.T. (1977a). Eighteen (18) month oral carcinogenicity study of R-802 (flumequine) in mice. Unpublished report from Riker Laboratories, Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. SIBINSKI, L.J., STEFFEN, G.R. & CASE, M.T. (1977b). Two-year oral toxicity-carcinogenicity study of R-802 (flumequine) in rats. Unpublished report from Riker Laboratories, Inc., St. Paul MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. SIBINSKI, L.J., STEFFEN, G.R. & CASE, M.T. (1979). Special 18-month toxicity study of R-802 (flumequine) in male mice. Unpublished report from Riker Laboratories, Inc., St. Paul, MN, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. WAZETER, F.X., GOLDENTHAL, E.I., GEIL, R.G., COOKSON, K.M. & HOWELL, D.G. (1971a). Subacute rang-finding study of S-10995 (flumequine) in monkeys. Unpublished report from International Research and Development Corp., Mattawan, MI, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France. WAZETER, F.X., GOLDENTHAL, E.I., GEIL, R.G. & HOWELL, D.G. (1971b). Fourteen-day oral toxicity study of flumequine in rats. Unpublished report from International Research and Development Corp., Mattawan, MI, USA. Submitted to WHO by Sanofi Santé Nutrition Animale, Libourne Cedex, France.
See Also: Toxicological Abbreviations Flumequine (JECFA Food Additives Series 51) Flumequine (WHO Food Additives Series 53) Flumequine (WHO Food Additives Series 39) FLUMEQUINE (JECFA Evaluation)