tek-monkey said:
Sorry, I can't where the results were misleading. I also can't see how animal testing caused the results to be misleading in any of these cases, merely that the scientists were flawed in the way they carried out some experiments.
First recorded case of birth defect in humans linked to thalidomide was in December 56, but the drug was released in 1957 regardless. Thalidomide didn't get recalled until 1962 in which time 10,000 children were born with deformities.
In those five years, scientists tried desparately to reproduce birth defects from thalidomide in animals despite already having proof that it occurred in humans. Animal testing didn't indicate a problem with thalidomide and its use persisted, delaying recall.
One breed of rabbit (White New Zealand) was affected but only then at 25 - 300 times the human doese. Some monkeys eventually displayed birth defects, but at 10 times the normal dose. Findings summarised by two scientists - "an unexpected finding was that the mouse and rat were resistant, the rabbit and hamster variably responsive and certain strains of primate were sensitive to thalidomide developmental toxicity. Different strains of the same species of animal were found to have highly variable sensitivity to thalidomide" - in other words no predictive value other than in the animal being tested.
Another scientist wrote " in approximately 10 strains of rats, 15 strains of mice, 11 breeds of rabbit, 2 breeds of dogs, 3 strains of hamsters, 8 species of primates and in other such varied species as cats, armadillos, guinea pigs, swine and ferrets in which thalidomide has been tested, teratogenic effects have been induced only occasionally".
That "thalidomide wasn't tested on animals" prior to release doesn't stand scrutiny. In a German medical journal of the time, it is stated animal tests were conducted, including on pregnant rodents. Time magazine in Feb 62 also states thalidomide was released "after three years of animal tests".
Whatever happened, animal based teratogenicity tests would never have been conclusive....
Another scientist: "There is at present no hard evidencve to show the value of more extensive and prolonged laboratory testing as a method of reducing eventual risk in human patients. In other words the predictive value of studies carried out in animals is uncertain. The statutory bodies such as the Committee on Safety of Medicines which require these tests does so largely as an act of faith rather than on hard scientific grounds. With thalidomide, for example, it is only possible to produce specific deformities in a very small number of species of animals. In this particular case, therefore, it is unlikely that specific tests in pregnant animals would have given the necessary warning: the right species would probably have never been used. Even more striking, the Practolol [birth defect] adverse reactions have not been reproducible in any species except man".
No amount of animal testing would have prevented the thalidomide disaster. In vitro research on human tissue would have done.