Teratogenic Effect of Chlormadinone Acetate in Mice and Rabbits

Oral administration of a large amount of chlormadinone acetate into pregnant mice and rabbits produced a large number of fetal malformations, such as cleft palate and others, while norethisterone with 1% mestranol showed no such teratogenic activity though its lethal effect on the fetuses was stronger than that of chlormadinone acetate. Norethynodrel with 2% mestranol showed the strongest lethal effect of the progestogens tested in mouse embryos, and cleft palate was induced in the surviving fetuses at 10 mg/kg. The dosage of the drugs which showed teratogenicity was generally much higher than human therapeutic or pharmacological doses in rabbits on the basis of maternal body weight.