Teratology study with the synthetic prostaglandin ONO-802 given intravaginally to rabbits

ONO-802, a synthetic E1 prostaglandin, was administered intravaginally via pessaries to Dutch belted rabbits at doses of 250, 62.5, and 12.5 micrograms/kg on days 6 through 18 of gestation. Rabbits in a vehicle control group were treated with pessaries that did not contain ONO-802 during the same period. Another group of animals remained untreated throughout gestation. Necropsies were performed on rabbits found dead and on those killed on gestation day 30. Body weight, food and water consumption, and clinical signs were monitored during the experiment. Major organs were weighed when the dams were necropsied on gestation day 30, and litter and fetal data were collected. Abortion and maternal deaths occurred in drug-treated groups. Body weight gains and food and water consumption were adversely affected by treatment particularly at the 250 and 12.5 micrograms/kg dose levels. Wastage (postimplantation loss) was significantly increased among treated groups (all dose levels), while other litter and fetal parameters were unaffected. ONO-802 was not teratogenic at maternal and embryotoxic dose levels.