Thalidomide as a teratogen appears to be highly species-specific. According to a review by Rogers and Kavlock (1996), the drug has been tested for prenatal toxicity in at least 19 laboratory species. These studies showed that limb malformations and increased resorption could be induced only in less commonly used rodent laboratory animals. Teratogenic effects similar to those observed in the human fetus have been reported for several rabbit strains, but at a much lower incidence rate. The monkey had been shown to be the most sensitive test species for thalidomide. Even in these nonhuman primates, the thalidomide effects can be induced typically only within the short time frame of 10 days to 2 weeks.

The animal studies conducted for the teratogenic effects of thalidomide are critical not only for elucidating the mechanism of the drug’s teratogenicity. They are also important in that certain teratogenic effects were proven to be highly time- and species-specific. The exact details of such a mechanism of action should be elucidated because certain teratogenic effects could also be specific to a certain chemical structure involved. To this day, the functional relationship between thalidomide’s chemical structure and its teratogenic action remains largely unknown. Some progress has been made, however, after more than 30 years later since the epidemic. According to Neubert et al. (1999), pronounced changes in the expression of surface adhesion receptors were observed during the embryonic differentiation and migration processes in primates dosed with thalidomide.