Teratogenic effects of 6-aminonicotinamide in mice.

6-Aminonicotinamide (6-AN), a potential broad-spectrum rodenticide, was examined for embryotoxic and teratogenic potential. Mice of the BALB/c strain were given a single oral dose of 1, 17, 34, 51 or 136 mg/kg on one of days 8 to 13 of gestation. Fetuses were either examined on day 18 post coitum (prenatal study), or allowed to go to term and examined 2 days after birth. Dam weights were significantly reduced (p less than 0.01) at dose levels of 17 mg/kg and greater. These same dose levels caused a significant decrease (p less than 0.01) in litter size and in mean fetal weight. They also caused an increase in the number of resorptions. Hydrocephalus and cleft palate were the most frequent visceral anomalies and were dose-dependent. Skeletal anomalies were also dose-dependent, and the fetus was most susceptible on days 8 to 10 post coitum. A significant (p less than 0.05) increase in the ratio of female to male fetuses was observed at dose levels of 34 mg/kg and greater. Surviving 2-day-old pups had few visceral anomalies but skeletal anomalies were more frequent. Because of its teratogenic properties, it would be difficult to register 6-AN for use against commensal rodents or as a broad-spectrum rodenticide for use in agricultural crops.