Fatal Mistakes of Animal Experiments Testing

4: Animal Tests Cannot Predict What Will Happen with New Medicines

Examples of Adverse Drug Reactions since Thalidomide (not predicted by animal experiments16 )
Aminorex Benoxaprofen Chloramphenicol Clindamycin Clioquinol Domperidone Halothane Isoprenaline aerosol inhalers Ketoconazole Methysergide Oral contraceptives Phenylbutazone Practolol Prenylamine Stilboestrol Suprofen Tycrynafen Zimediline	pulmonary hypertension fatalities, phototoxicity aplastic anaemia intestinal disease neurotoxicity cardiotoxicity jaundice asthmatic deaths liver damage retroperitoneal fibrosis blood clots aplastic anaemia eye, skin and abdominal toxicity cardiotoxicity vaginal cancer in female offspring kidney dysfunction, side pain fatatities neurotoxicity

In most cases, animal tests cannot predict what will happen when a new medicine is given to people.17 But the tests not only give a false sense of security, there is also the risk that worthwhile therapies may be lost or delayed through toxic effects that do not occur in human beings. A review of 45 drugs by Britain’s Committee on Safety of Medicines found that animal experiments were most likely to predict vomiting and gastrointestinal disturbances. Overall, however, the survey found that, at best, just 25% of the harmful effects observed in animals actually occurred in people.18

Examples include propranolol, a now widely used beta-blocking drug for heart disease and high blood pressure. Development was put in jeopardy when it caused rats to collapse and dogs to vomit severely.16 On the basis of animal tests, the transplant drug tacrolimus was feared too toxic for human use, and if it hadn’t been given as a last chance option to desperate patients, its life-saving qualities may never have been appreciated.19 And the discovery that tamoxifen caused cancer in rats would have stopped development of this important anti-cancer agent had the company ICI not already been reassured by its safety profile in human patients.16

A well known but potentially far-reaching case is penicillin. Howard Florey, who developed the drug for therapeutic use, later admitted it was a 'lucky chance' that mice rather than guinea pigs had been used: ‘If we had used guinea pigs exclusively we should have said that penicillin was toxic, >>

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