In the late 1950s and early 1960s, many babies were born with limb malformations after expectant mothers had taken Contergan (Thalidomide) for insomnia during pregnancy. This drug had been tested in animals and was deemed safe. Do animal experiments convey a false sense of security?
No matter how safe tests may be, the risk of undesirable effects can only be minimised; it can never be ruled out entirely.
Thalidomide, the active ingredient of Contergan, a sedative and sleeping pill, had been tested on rodents before it was launched on the market in the 1950s. The damage caused to human embryos by Contergan during the first few weeks of pregnancy was not discovered in the animal experiments. Standard testing with pregnant animals was not common practice at the time. Shortly after the Contergan scandal broke, experiments were carried out with pregnant rabbits, and they developed exactly the same malformations as those seen in humans. Thus, had Thalidomide been tested in pregnant animals, the alterations involving the animal embryos would in all likelihood have been discovered and it would have been known that this substance is extremely harmful to embryos. Nowadays, such (teratological) testing is a compulsory part of the preclinical development of a medicinal product.
In cell tests, Thalidomide is neither toxic nor does it alter the genetic makeup. Hence, the malformations would probably not have been discovered with the alternative methods available to us today. This shows why abandoning the use of animals altogether is not feasible.