Developmental toxicity evaluation of the new fluoroquinolone antibacterial DW-116 in rats

Effects of moxifloxacin and clinafloxacin on murine limb buds cultured in regular and in magnesium-deficient medium

Evaluation of the prenatal toxicity of a substance in rats or other animals according to the current guidelines is often hampered by the rapid metabolism of the test compound and/or by maternal toxicity. One example for such a compound is moxifloxacin. In vitro systems offer the possibility to study the direct effects of the test compound on embryonic tissues. The aim of this study was to evaluate the embryotoxic potential of moxifloxacin in vitro using the murine limb bud culture. Clinafloxacin, which was found to be teratogenic when tested in rats, was used for comparison. The effects of various concentrations of moxifloxacin (10, 30, 60 and 100 mg/L) and clinafloxacin (3, 10 and 30 mg/L) on growth and differentiation of 12-day-old murine limb buds were studied in a standard and in a magnesium-deficient medium. After termination of the culture, the respective front limb buds were examined by different methods. Clinafloxacin showed clear-cut effects at a concentration of 30 mg/L in both media. Effects were similarly pronounced as the effects observed with moxifloxacin at a concentration of 100 mg/L. Lower concentrations of moxifloxacin, which are achieved during therapy in humans, did not impair growth and differentiation of limb buds. Using electron microscopy, slight ultrastructural changes could be seen after exposure to 3 mg clinafloxacin/L medium. Ultrastructurally, clinafloxacin caused a concentration-dependent decrease of the extracellular matrix, swelling of cell organelles and at higher concentrations necrotic chondrocytes. These effects were significantly enhanced in a magnesium-deficient medium. In conclusion, the effects of moxifloxacin on murine limb buds in vitro were definitely less pronounced than those of clinafloxacin. Effects on growth and differentiation occurred with moxifloxacin only at concentrations that are higher than plasma concentrations observed during therapy. This result is of special interest, because due to rapid metabolism of moxifloxacin in rats results from a routinely performed segment II type study cannot be used for a risk assessment.

Peri- and postnatal developmental toxicity of the fluoroquinolone antibacterial DW-116 in rats

DW-116 is a fluoroquinolone antibacterial developed by Dong-Wha Pharmaceutical Industry Co. The aim of this study is to determine the potential adverse effects of this chemical on pregnancy, delivery and lactation of dams and on peri- and postnatal development of F1 offspring. The test chemical was orally administered to pregnant rats from day 16 of pregnancy, through parturition and throughout the period of lactation up to weaning (postnatal day 21) at dose levels of 0, 10, 50, or 250 mg/kg/day. The progeny were examined at birth and subsequently to weaning. Mortality, body weight change, physical signs of postnatal development (pinna detachment, incisor eruption, fur development, eye opening, testis descent and vaginal opening) and behavioral function (righting reflex, negative geotaxis, grip-strength, pupillary reflex, acoustic startle response, rotating rod test, open field test and water-filled T-maze test) were evaluated. When the exposed offspring reached maturity (11 weeks old) their reproductive capacity was assessed. Maternal toxicity was observed only in the highest dose group and was limited to decreased food consumption during the late stage of pregnancy. However, this change was not observed during the lactation period. There were no adverse effects on mortality, clinical signs, body weight, necropsy findings, organ weight of dams in any treatment group. No adverse effects on the offspring were seen with the low and middle doses tested, but the highest dose increased postnatal mortality. The number of stillborn was also increased at the highest dose but the difference was not statistically significant. Meanwhile, no treatment-related effects were observed in clinical sign, developmental and behavioral landmarks and necropsy findings at any dose levels tested. There were no treatment-related effects on the mating of the F1 generation and resulting F2 offspring. The results of this study indicate that the peri- and postnatal administration of DW-116 to female rats results in an increase in postnatal mortality at a minimally maternotoxic dose, i.e., 250 mg/kg/day. Under the experimental conditions, the no-observed-adverse-effect level for peri- and postnatal developmental toxicity was considered to be 50 mg/kg/day.

Effects of prenatal exposure to the environmental pollutant 2-bromopropane on embryo-fetal development in rats

2-Bromopropane (2-BP), a halogenated propane analogue, is a substitute for chlorofluorocarbones. The present study was carried out to investigate the potential adverse effects of 2-BP on pregnant dams and embryo-fetal development after maternal exposure on gestational days (GD) 6 through 19 in Sprague-Dawley rats. The test chemical was administered subcutaneously to pregnant rats at dose levels of 0, 250, 500, and 1000 mg/kg per day. All dams were subjected to caesarean section on GD 20 and their fetuses were examined for external, visceral and skeletal abnormalities. In the 1000 mg/kg group, maternal toxicity included an increase in the incidence of abnormal clinical signs, a suppression in the body weight and body weight gain, and a decrease in the food intake. Developmental toxicity included an increase in the fetal deaths, a decrease in the litter size, and a reduction in the fetal body weight. In addition, an increase in the incidence of fetal external, visceral, and skeletal abnormalities was seen. In the 500 mg/kg group, minimal developmental toxicity including decreased fetal body weight and increased fetal ossification delay was observed. There were no adverse effects on either pregnant dams or embryo-fetal development in the 250 mg/kg group. These findings suggest that a 14-day subcutaneous dose of 2-BP is embryotoxic and teratogenic at a maternally toxic dose (i.e., 1000 mg/kg per day) and is minimally embryotoxic at a nonmaternally toxic dose (i.e., 500 mg/kg per day) in Sprague-Dawley rats. In the present experimental conditions, the no-observed-adverse-effect level (NOAEL) of 2-BP is considered to be 500 mg/kg per day for dams and 250 mg/kg per day for embryo-fetal development.

Effects of 2-bromopropane on pregnant dams and embryo-fetal development in the ICR mouse

2-Bromopropane (2-BP), a halogenated propane analogue, is a substitute for chlorofluorocarbones (CFCs) which have a great potential to destroy the ozone layer and to warm the earth's environment. The present study was carried out to investigate the potential adverse effects of 2-BP on pregnant dams and embryo-fetal development after maternal exposure during the gestational days (GD) 6-17 in ICR mice. The test chemical was administered subcutaneously to pregnant mice at dose levels of 0, 500, 1000, and 1500mg/kg per day. All dams were subjected to caesarean section on GD 18 and their fetuses were examined for external, visceral and skeletal abnormalities. Throughout the study period, no treatment-related deaths were found in the groups treated with 2-BP. Pregnant mice of the 1000 and 1500mg/kg groups showed treatment-related clinical signs such as rough fur and swelling, induration, crust formation, and ulceration in the injection sites which were dose dependent in incidence and severity. A decrease in fetal weight, an increase in fetal malformation, and an increase in fetal ossification delay were found at a dose level of 1500mg/kg per day in a dose-dependent manner. On the contrary, there were no adverse effects on body weight, body weight gain, gravid uterine weight, food consumption, gross finding at any dose tested. In addition, no treatment-related effects on the number of corpora lutea, implantations, resorptions, dead fetuses, live fetuses, and sex ratio of live fetuses were observed. These findings suggest that 2-BP was embryotoxic and teratogenic at a minimally maternally toxic dose (i.e., 1500mg/kg per day) in ICR mice. In the present experimental conditions, the no-observed-adverse-effect level of 2-BP is considered to be 500mg/kg per day for dams and 1000mg/kg per day for fetuses, respectively.