Aspirin: teratogenic evaluation in the dog.

Beagle bitches were administered aspirin at either 100 or 400 mg/kg/day between Days 15 and 22 or Days 23 and 30 postmating, and corresponding control groups were dosed with vehicle during one of these same time periods. Maternotoxicity was evident in all dogs dosed with 400 mg/kg/day of aspirin, but no signs of toxicity were observed when 400 mg/kg/day of aspirin was administered from Days 15 to 22 postmating. Teratogenicity, as evidenced by 50% malformation rate, was seen in fetuses from dams treated with 400 mg/kg/day on Days 23 to30 postmating. Observed malformations included, but were not limited to cleft palate,micrognathia, anasarca, cardiovascular malformations, and tial anomalies. No evidence of embryotoxic or teratogenic effects was seen in fetuses from either 100 mg/kg/day dosage level group. Examination of fetuses from 12 untreated litters and 4 vehicle-control litters revealed a very low spontaneous malformation rate confined almost entirely to minor tail abnormalities. These data support use of the dog as an acceptable alternative species in teratogenic screening.