International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

93: Flexible Animal Test Support Rival Theories

A new animal test raised fears that Astra's ulcer treatment, omeprazole, may cause stomach cancer. In the test, developed by Glaxo pharmaceutical company, rats are dosed with the suspect drug or chemical, after which tissue samples are removed from the animal's stomach and analysed for effects on DNA, the substance which controls proper development of the cells. Interference with DNA is regarded as a possible first step to cancer.

The experiments showed that omeprazole damaged the DNA but that ranitidine, Glaxo's own antiulcer drug, did not.(1) On the basis of these results, Glaxo halted comparative clinical trials of ranitidine (Zantac) and omeprazole, an action, according to the Lancet, that seemed certain to influence prescribing habits.(2)

In response, Astra, the makers of omeprazole, argued that "the method used by Glaxo is scientifically unsound and the results therefore have no clinical consequences."(3) They noted that "long term studies in which omeprazole was administered for up to 2 years in rats, 18 months in mice, and 1 year in dogs yielded no evidence for a direct carcinogenic potential, in the stomach or elsewhere."


1) B.Burlinson et al, Lancet, 1990, February 17, 419.
2) Lancet, 1990, February 17, 386
3) L Ekman et al, Lancet, 1990, February 17, 419-420.

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