Abnormal embryogenesis induced by thiopental

The effects of thiopental on chick embryos were analyzed in the present study. Thiopental was dissolved in saline and injected into embryonating chicken eggs at doses ranging from 0.2 to 4.0 mg per egg. The injections were made into the air sacs of eggs after two to four days of incubation. Control eggs were injected with an equivalent volume of saline (0.1 ml per egg). In all 1080 chicken eggs were used for this study. All embryos were examined on day 7. The LD50 for eggs injected on days 2, 3 and 4 was 2.1, 1.9, and 4.1 mg per egg, respectively. The principal malformations observed were exencephaly, anencephaly, twisted limbs, twisted neck, microphthalmia, everted viscera, and hemorrhage above the left eye and in both cerebral hemispheres. The results of the present study indicate that thiopental has a tendency to cause malformations in the chick embryos tested.