During the 1960s, Japan suffered a devastating epidemic of drug-induced disease associated with clioquinol, the main ingredient of Ciba-Geigy's antidiarrhoea medicines Enterovioform and Mexaform. At least 10,000 people, and perhaps as many as 30,000, were victims of SMON (subacute myelo-optic neuropathy), a new disease whose symptoms include numbness, weakness in the legs, paralysis and eye problems, including blindness.(1) In 1970 Japan's Ministry of Health and Welfare banned the drug and 15 years later clioquinol was withdrawn worldwide.
Clioquinol's harmful effects result from nerve damage yet animal experiments performed by the company revealed "no evidence that clioquinol is neurotoxic", tests being carried out on rats, cats, beagles and rabbits.(2)
Although some argue that "Animal tests have consistently failed to reproduce the effects seen in humans,”(3) researchers at the Okayama University Medical School say they have induced clioquinol toxicity in mongrels.(4) Nevertheless, they note that different species respond differently, with monkeys, hens, cocks, and mice only mildly affected even after higher doses. They also found that beagle dogs were 3-4 times less sensitive to clioquinol than mongrels, and concluded that “These facts suggest strongly differences in strains as well as species of animals for the neurotoxicity of clioquinol.”
1) Lancet, 1977, March 5, 534.
2) R.Hess et al, Lancet, 1972, August 26, 424-425.
3) W.Sneader, Drug Development: From Laborator,v to C/inic (Wiley)
4) J.Tateishi et al, Lancet, 1972, June 10, 1289-1290.
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