How Reliable are Animal Experiments?

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    How Reliable Are Animal

    Experiments ?

    Uncovering the failure rates from animal labs

    An inquiry into animal experiments is long overdue, as there has never

    been a formal evaluation of animal testing.

    However, there have been smaller scale statistical studies, and they

    make interesting reading.

    Drug Testing

    Animal experiments are an established method of safety testing medical

    drugs. Although this was never evaluated before the method wasadopted, adequate data is available.

    Animals of various species are used to screen drugs for potential

    unwanted reactions. Given that it is normal practice to use a number of

    species, it might be expected that if animal experiments were predictive,

    this method would identify potential dangers.

    Animal experiments were evaluated by animal experimenters, whotook six drugs, and noted which of the 78 adverse effects were

    detectable in dogs or rats. They ignored the effects which were

    undetectable in animals (e.g. headaches). Less than half (46%) of

    the remaining side effects were detected in the animals - slightly less

    than the expected results from flipping a coin[1]. In other words,

    animal tests were wrong 54% of the time.

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    54% failure

    With such a high failure rate, it might be expected that a high proportion

    of side effects caused by drugs would go unpredicted by animal

    tests. With this in mind, the American Food & Drug Administration (FDA)

    monitored all the drugs approved over a ten-year period.

    Of 198 drugs monitored, 102 (52%) were re-labelled or withdrawndue to unforeseen effects[2]. As some of the side effects

    that were predicted would have been discovered by pre-approval

    human trials, the success rate of animal use can be safely assumed

    to be well below the 48% discovered by the FDA.

    52% failure

    An international authority on the matter who represented the World

    health Organization failed to put a figure on the success rate of standard

    vivisection practice when he stated:

    "Most adverse reactions which occur in man cannot bedemonstrated, anticipated or avoided by the routine subacute and

    chronic toxicity experiment."[3]

    Where he avoided estimating a percentage, Dr Ralph Heywood did

    not. As Scientific Executive of Huntingdon Research Centre (now

    Huntingdon Life Sciences), one of the largest animal labs in Europe

    concerned with screening drugs, he estimated that:

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    "the best guess for the correlation of adverse reactions in man andanimal toxicity data is somewhere between 5% and 25%." [4]

    75%-95% failure

    Interestingly, his estimation of a maximum of 25% is agreed on by Dr AP

    Fland:

    'As a very approximate estimate, for any individual drug, [only] upto twenty-five per cent of the toxic effects observed in animal studies

    might be expected to occur as adverse reactions in man'.[5]

    More than 75% failure

    This has terrible consequences, whihc you can read abouthere.

    But sometimes the reverse is true. Unwanted effects may be predicted by

    animal studies, when they do not affect humans. For example, the first

    chemotherapy drug, Actinomycin-D, was discovered without animal

    use. Later it was tried on animals and found to kill many species,

    including monkeys. This did not relate to humans. This is common:

    45 drugs tested in 1978 were analysed. Of the side effects predictedby animal studies, 75% did not happen in humans[6].

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    75% failure

    Along with the matter of whether a drug is actually effective or not, the

    safety profile of a potential new drug is assessed first on animals, thenprogressing to human trials if successful in animals. So the success rate

    of animal tested drugs in humans can again be evaluated by examining

    the progress of these medicaments.

    The Pharmaceutical Research and Manufacturers of America estimatethat

    of the drugs presented to human trials, 5% are eventually

    approved[7].

    95% failure

    The human trials are in three stages. The first trial involves healthy

    human volunteers, typically about 20-80.

    At this stage eleven out of twelve animal-modelled drugs fail[8].

    92% failure

    An example of this - an example which has produced statistical evidence -

    is the case of stroke drugs.

    In the periods 1978-1988, twenty-five drugs were found to treatstroke in animals. The number that worked in humans was found to

    be zero[9].

    100% failure

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    Twenty-two drugs to treat spinal cord damage were developed onanimals. None worked in humans.[10]

    100% failure

    An approach such as animal experimentation to discovering drugs can be

    likened to gambling. Occasionally - through sheer chance - it may give

    the correct result applicable to humans. But it cannot be relied on. A

    famous pharmacologist said on accepting a prize for his work that is it "a

    matter of pure luck that animal experiments lead to clinically useful

    drugs". He was among those who used animals for exactly that when he

    said this[11].

    Why don't animal methods work for predicting drug reactions? The

    simple answer is that animals are different. A major difference is that

    they suffer from different diseases to us. Less than 2% of the illnesses

    that can afflict humans are found in any other animal species[12]. So

    many of the diseases animal experimenters are trying to treat - as well as

    many of the conditions which may be caused as a side effect of aprospective medication - may not exist in the test animal (or any

    animal). Dogs get distemper, humans do not. This is also why no

    animals have developedAIDSin the same way that humans have.

    Animals also have different biochemistry, different diets, they don't live as

    long as us (and the test periods are over short periods) - and they

    process drugs differently. Vitamins affect different animals in different

    ways, and the drugs are digested and metabolised differently. Animal

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    experimenters have discovered that rats metabolise drugs in a different

    way to humans in 83% of cases[13]. Yet still they are a favourite tool for

    drug testing and chemical screening. Why?

    Dr James G Gallagher was director of Medical research, Lederle

    Laboratories, when he discussed "an unscientific preoccupation with

    animal studies." He went on to say "Animal studies are done for legal

    reasons and not for scientific reasons."[14]

    It gets drugs onto the market, and provides evidence that something was

    done, therefore avoiding the charge of negligence when the inevitable

    human damage occurs.

    Cancer

    Another area where animal use is claimed to be essential is incancerresearch. Animals are used to see which chemicals cause cancer, and

    which may help combat it.

    The screening of potential cancer-causing chemicals is a subject in which

    vivisection has been evaluated. The drug company Pfizer did this in 1983.

    "The results would be vitally important because despite costingmillions of dollars, no one really knew whether they provided

    adequate protection against hazardous substances. Human findings

    were compared with experimental data from rats and mice for all

    chemicals known to cause cancer in people. The outcome was

    disturbing: in most cases animal tests had given the wrong

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    answer. The report concluded that we would have been better off to

    have tossed a coin[15]."

    The actual percentage of carcinogens identified was 36.8%

    63% failure

    Rats and mice are still overwhelmingly the most commonly used

    animals. But the use of other animals is no more successful.

    "Warning is given not to carry over, without reservation, to man, theconclusions based on animal experiments. In monkeys none of the

    power carcinogens [to humans] has been shown to produce

    cancers."[16]

    100% failure

    Which means that approval by experiments on monkeys means nothing

    for our safety. More data to evaluate the methods is available from the

    study or oral cancers:

    Nineteen chemicals known to cause oral cancer in humans werestudied in animals. Using the standard National Cancer Institute

    Protocol, and rats and mice, twelve were found to be safe in

    animals[17].

    63% failure

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    Also the reverse is true - substances identified as dangerous by animal

    experiments are likely to be completely harmless.

    Of twenty compounds known not to cause cancer in humans,nineteen did cause cancer in the laboratory animal[18].

    95% failure

    Differences between species are so specific that even relatively similar

    species may show a different profile of reactions to test chemicals.

    Experiments on rats and mice show that 46% of chemicals whichcaused cancer in rats, were not cancer inducing in mice. Mice were

    found to develop cancer, due to exposure to chemicals which did not

    affect rats[19].

    Industry experts correctly conclude: "We would have been better off totoss a coin"[20] Animal experimenters involved in the practice have

    themselves evaluated their business as "a half-baked guess" and "all

    guess" (Dr Frederick Coulston)[21].

    Animals are also used in attempts to detect drugs and plants that may be

    useful in treating human cancers. Yet this has not been effective. As the

    executive director of cancer research at Merk Research Laboratorysummed up: "The fundamental problem in drug discovery for cancer is

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    that the model systems are not predictive at all"[22]. Model systems that

    use animals.

    The lack of success with animal models is not due to a lack of

    trying. Between 1970 and 1985, 500,000 different chemicals were tried

    on animals in an attempt to find some which would combat cancer.

    From this mammoth operation, just eighty drugs were identified bythe animal studies. Of these eighty, only twelve went on to make a

    different to the lives of humans.

    85% failure

    At a first glance this might seem to be a worthwhile exercise -

    somethingworthwhile came out of this massive project. Yet all of these

    new treatments were sufficiently similar to existing treatments that they

    could have been identified from their chemical structure. Using no

    animals and a fraction of the time and money, non-animal, human basedmethods could have had these drugs in use more quickly[23].

    A similar study, over 25 years by the National Cancer Institute (USA)

    tested 40,000 plant species for anti-cancer effects.

    All chemicals identified by the animal tests were either ineffective ortoo highly poisonous to be used in humans[24].

    Even the Handbook of Laboratory Animal Science admitted: "despite 25

    years of intensive research and positive results in animal models, not a

    single anti-tumour drug emerged from this work."[25]

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    100% failure

    One of the major reasons for this is that the cancers that humans develop

    are not the same as the animal cancers. With this in mind, experimentershave tried to improve their success rates by implantinghuman cancers

    into mice. Known cancer drugs were used on the animals.

    In 30 of the 48 cases, the human drugs had no affect on the cancer,despite working in humans, and the cancers in question being human

    cancers[26].

    63% failure

    The species differences exist on too many, and on too subtle levels to be

    bypassed. As Irwin Bross, formerly of the Roswell Park Memorial Institute

    for Cancer Research stated when giving evidence to the US Congress in

    1981:

    "while conflicting animal results have often delayed and hamperedadvances in the war on cancer, they have never produced a single

    substantial advance in either the prevention or treatment of human

    cancer."

    100% failure

    Instead, research has been led in the wrong direction, studying the wrong

    form of cancer in the wrong species.

    "God knows we've cured mice of all sorts of tumours" said Thomas E

    Wagner, a long-serving cancer research specialist. "But that isn't medical

    research."[27]

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    Why do they do this? Let someone who does this answer this

    question. Dr P Shubik was at a conference of cancer researchers who

    used animals. Many had openly criticised their work and stated how

    unscientific it was.

    "The chief objective is to keep us all employed, and to make sure wedo interesting experiments so that we can come back to these nice

    places."[28]

    Read more about cancer researchhere.

    Birth Defects

    Perhaps the greatest fear among ordinary people is that of the damage

    drugs can do to theirunborn children. The example of Thalidomide,

    which caused thousands of serious birth defects, has been quoted as a

    reason why animal experiments mustbe done - to stop it happening

    again.

    It has been claimed that thalidomide was never tested on pregnant

    animals before it was given to humans, although this is unlikely. Animal

    experiments were standard practice. It is undisputed that after the

    human disasters it was tested on animals.

    Countless species and sub-strains were used, including over 150different breeds of rabbit. One species of rabbit produced malformedoffspring when given Thalidomide - and that was at doses of 10

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    times the human dose. Salt or sugar in that dose would have caused

    the same problems. Animal experiments were - and still are -

    incapable of predicting that thalidomide is dangerous to pregnant

    humans[29].

    100% failure

    Experiments have been conducted to evaluate whether animal

    experiments are effective in showing which drugs can damage the unborn

    child. Drugs known to damage the human foetus were given to animals.

    55% passed tests on hamsters[30].

    55% failure

    70% passed tests on pregnant monkeys - our closest animalrelative[31].

    70% failure

    Yet other drugs and chemicals have been identified to be dangerous to

    pregnant mothers by animal experiments despite being harmless. As

    reported in a medical journal, over 1,200 chemicals have been identified

    to cause birth defects in lab animals, yet only 30 cause birth defects in

    humans[32]. Many useful drugs are indicated dangerous in animals but

    are safe in humans, including aspirin and insulin[33].

    97.5% failure

    This estimate of 97.5% failure invites disbelief, but was arrived at

    independently:

    More than eight hundred chemicals have been identified as teratogens in

    laboratory animals, but only a few of these, approximately twenty, have

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    been shown to be teratogenic in humans. This discrepancy can be

    attributed to differnces in metabolism, sensitivity and exposure

    time.[34] This is also 2.5%.

    97.5% failure

    Now that animal experiments are an established, commonly used method,

    it is known that all drugs released have been tested on pregnant animals

    first. Yet of all birth defects, an estimated 61% of them were estimated

    to be caused by medical drugs, according to one of the most detailed

    studies ever conducted[35]. For stillborn babies, drugs are estimated to

    be the cause in 88% of cases[36].

    Birth defect rates are rocketing. Over a 25-year period from 1948 to

    1973, they rose from 3 per 100,000, to 500 per 100,000[37]. They are

    continuing to rise. Read more about thishere.

    Evidence taken from the results of animal experiments enable us evaluate

    the accuracy of their tests. Many good scientists expect that due to themassive differences in species, which can never be overcome, the

    accuracy will be low. Other people have looked at the results and come

    to a similar conclusion.

    The average of the percentages uncovered above is 20%. But even this

    figure may be flattering. Much of animal experimentation is attempting to

    recreate a condition already known.

    "until somebody knew what to look for, they did not seek thosethings. To suggest that this process is predictive is somewhat of an

    anomaly in terms. It can hardly be predictive after the fact"[38]

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    If animal testing were abandoned today, there would behundreds of

    methods we could use. The American National Cancer Institute alone

    uses 100 cell culture tests to identify cancer-causing chemicals[39]. As

    technology progresses we are able to develop more accurate

    methods. Gene therapy and computers are just two examples of areaswhere massive advances have been made using ingenuity and good

    science.

    All these methods have the advantage of being human-centred and

    therefore can expect a degree of accuracy far in excess of the extremely

    low levels achieved by animal experiments. 20% effectiveness is not

    science. It is the sort of success rate achieved by the charlatan fortune-teller.

    Medical advances have been made throughout history by studying

    patients, observing results, studying cells and human tissue, autopsies,

    the use of mathematical techniques and computer modelling and studying

    populations. These methods have been successful, while animal

    experiments have been haphazard and have failed us.

    This article may be copied and circulated with the aim of educating more people of the

    failure of vivisection.

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    5 Dr. A. P. Fland, Journal of the Royal Society of Medicine, vol.71, 1978, pp.693-696.

    6 AP Fletcher in Proc R Soc med, 1978;71, 693-8

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    27 The Columbus Dispatch, March 20 1998

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