World famous toxicologists Zbinden and Flury-Rovesi comment:

"An LD50 does not give direct indication of the acute (short term) toxicity of a compound, but only of its lethal potential."

and...

"For the recognition of the symptomology of acute poisoning in man and for the determination of the human lethal dose, the LD50 in animals is of very little value."

and...

"When we administer a new compound to animals we must never forget that only a small percentage of the toxic side effects which may occur in humans will manifest themselves in the course of the animal experiment."

and...

"From all the considerations it must be concluded that the results of an LD50 test even if it were conducted with the greatest care, must be regarded as an isolated biological finding that cannot make a claim to universal and perpetual validity."
- Arch. Toxicol (1981) 47:77-99.

"Specific attention should be focused on the experiment euphemistically called the LD50 test. This is a nice way of saying that the lethal dose of a substance is determined when half the animals in an experimental batch die."
- Editorial, Daily Telegraph, 28 October 1982.

The following extract is taken from:
Compound 1080 Properties and Use of Sodium Monofluoroacetate in New Zealand

"Dogs

The LD50 of 1080 for dogs is generally accepted as 0.07 mg/kg. Individual dogs vary widely in their susceptibility as may be seen from typical results of a dosing trial on impounded dogs... The LD50 calculated from the results of this trial is 0.07 mg/kg even though a dose of 0.07 mg/kg killed only 25 percent of the dogs.

This illustrates the wide variations that occur and the need for caution in using LD50 figures."

There follows a detailed account of the sufferings of poisoned dogs and other animals at Wallaceville Research Laboratories.

"During a recent visit to a medium-sized European pharmaceutical company I enquired about the number of animals used in toxicology in 1981. Of 21,210 rodents, over 60% were sacrificed for the study of acute toxicity, the great majority of them being utilised in LD50 tests."
- Prof. G. Zbinden, Institute of Toxicology, University of Zurich.

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