International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

91: The Opren Affair

The arthritis drug Opren (Oraflex in the US) was withdrawn from the world market in August 1982 following British reports of deaths and serious liver damage in people taking the drug.(1) Since 1980, when Opren was first introduced in the UK, there had been 3,500 reports of harmful effects with 61 deaths, mainly in elderly patients.(2)

Scientists list Opren as a drug whose injuries were not predictable from animal tests,(3) and note that "despite searching preclinical animal toxicity studies... administration to rheumatoid patients resulted in adverse reactions including onycholysis (nail damage) and skin phototoxicity (light sensitivity) and finally in fatal hepatotoxicity (liver damage) whereupon the drug was withdrawn". And Dista, the subsiduary of Eli Lilly who marketed the drug in Britain, stated in their literature that "the effects of benoxaprofen (Opren) in the rhesus monkey were studied for one year...There were no apparent adverse effects on survival."

Researchers believe that the fatal cases of liver damage might have been averted by more extensive clinical trials,(3) especially in the elderly who take much longer to eliminate Opren from the body than either young people or laboratory animals.


1) E.M.B.Sorensen, Toxicology Letters, 1986, vol.34, 277-286.
2) British Medical Journal, 1982. August 14, 459-460.
3) C.T.Eason et al, Regulalory Toxicology & Pharmacology, 1990, vol.11, 288-307.

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