International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

88: Antibiotics, Guinea Pigs & Hamsters

Years of experimentation have taught scientists that guinea pigs and hamsters are especially sensitive to the harmful effects of antibiotics. For instance, widely prescribed human antibiotics such as ampicillin, amoxycillin and oxytetracycline are considered "toxic" and therefore inappropriate for use in these species.(1) Another example is erythromycin where the usually recommended human dose is enough to kill a hamster!(2)

Today, "it is generally recognised that the guinea pig is peculiarly sensitive to the lethal effects of antibiotics,"(3) but this was not always realised. In his book Drug Development: From Laboratory to Clinic, Dr Walter Sneader describes how "it was fortunate that Florey and Chain did not decide to use guinea pigs when first testing penicillin, for they may then have abandoned the project as these animals are hypersensitive to penicillin". Florey and Chain were the Oxford scientists who carried out animal tests following Fleming's discovery of penicillin. Florey later commented "...mice were tried in the initial toxicity tests because of their small size, but what a lucky chance it was, for in this respect man is like the mouse and not the guinea pig. If we had used guinea pigs exclusively we should have said that penicillin was toxic, and we probably should not have proceeded to try to overcome the difficulties of producing the substance for trial in man.(4)


1) A.A.Tuffery (ed.), Laboratory Animals - An lntroduction for New Experimenters (Wiley, 1987).
2) A single, minimum recommended dose of erythromycin is 250-5OOmg every 6 hours i.e. 3.5-7.0 mg/kg for a 70kg person. The lethal dose for hamsters is 3.5mg/kg (ref.3)
3) S.J.Desalva et al, Toxicology & Applied Pharmacology, 1969, vol.14, 510-514.
4) H.Florey, Conquest, January, 1953.

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