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With EDM 400 highlighting penicillin, here is Alexander Fleming on the disaster of animal models

Parliamentary EDM 400  refers to penicillin as an example of the harm caused to human patients by animal models: penicillin was delayed for human use by more than 10 years because it has no effect on rabbits. Here is Alexander Fleming, the great scientist who discovered penicillin, on the misleading role of animal experimentation:

‘How fortunate we didn’t have these animal tests in the 1940’s, for penicillin would probably never been granted a license, and possibly the whole field of antibiotics might never have been realized’. [1]

Howard Florey also played a crucial role in bringing about the use of penicillin for humans; here is Florey on animal models:

‘Mice were used 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 and overcome the difficulties of producing the substance for trial in man. [2] (Emphasis added).

For a brief history of the discovery of penicillin, and the role lab animal models played in delaying this life saving medicine for human patients, please visit this link.


1. Parke DV: Clinical Pharmacokinetics in Drug Safety Evaluation. ATLA 1994, 22:207-209.

2. Florey H: The advance of chemotherapy by animal experiment. Conquest 1953, 41:12.