Teratology and reproduction studies with triclopyr in the rat and rabbit

Triclopyr (3,5,6-trichloro-2-pyridyloxyacetic acid), being developed as a new herbicide for use on brush and weeds, was evaluated for its potential effects on reproduction, and embryonal and fetal development. Pregnant Sprague-Dawley rats were given doses of 0, 50, 100, or 200 mg/kg/day by gavage on Days 6 through 15 of gestation. Dose-related signs of maternal toxicity were observed during the treatment period. No teratogenic effects were observed at any dose level, though slight fetotoxicity, possibly secondary to maternal toxicity, occurred at the high dose level (200 mg/kg/day). Pregnant New Zealand White rabbits were given doses of 0, 10, or 25 mg/kg/day by gavage on Days 6 through 18 of gestation which produced transient, dose-related decreases in maternal body weight gain. However, there were no indications of any treatment-related effects on fetal growth and development among rabbits. Male and female Sprague-Dawley rats maintained on diets supplying 0, 3, 10, or 30 mg/kg/day over three generations exhibited no consistent treatment-related effects on reproductive performance, pregnancy, parturition, or neonatal survival. These data indicated that triclopyr had little or no potential for teratogenic or reproductive toxicity even when the level of exposure approached that which elicited maternal toxicity.