International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

33: Morphine Madness

Morphine remains the most valuable analgesic for severe pain (1) yet has such a peculiar effect in some species that had it been tested on, say cats, prior to human studies, it could have been rejected. In these animals the drug produces a condition known as "morphine mania" which leaves them highly excitable and apprehensive. Their movements are irregular and jerky, and their pupils are abnormally dilated.(2) While morphine produces hyperexcitement in cats, it has the opposite, calming effect in people.(3) Furthermore, their pupils may be contracted.(1) Fortunately the drug was discovered through human studies and only later tested on animals. (4)


1) British National Formulary, no.26 (BMA & the Royal Pharrnaceutical Society of G.B.,1993).
2) F.M.Sturtevant & V.A.Drill, Nature, 1957, June 15, 1253.
3) B.Brodie, Clinical Pharmacology & Therapeutics, 1962, vol.3, 374-380.
4) J.T.Litchfield in Drugs in our Society, Ed. P.Talalay (Johns Hopkins, 1964).

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