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May 1995
Drug Testing on Trial

By Robert Wilbur


I had two encounters with a drug called phenylbutazone (Butazoladin), one in a human being and one in a dog. The human being was my father, who nearly died of heart failure caused by phenylbutazone, a powerful non-steroidal anti-inflammatory agent that had been mindlessly prescribed for a trivial muscular ache. Some time later, my then-sixteen year old pit bull, Suzy, became increasingly crippled by arthritis of the spine. Her vet, Dr. Paul Cavanagh of the Westside Veterinary Hospital in New York City, wanted to prescribe phenylbutazone. I was taken aback by the suggestion, but Paul assured me that phenylbutazone can be given safely to dogs. And in fact, Suzy tolerated phenylbutazone without any problems.

This is just one example of a drug whose toxicity differs in human and non-human animals. The scientific literature is replete with similar examples, leading to the conclusion that drugs differ in their effectiveness, rate of metabolism, and toxicity in different species. Some side effects can’t even be measured in animal experiments. Thus, in one comparative survey of six different drugs given to rats, dogs, and humans, 89 different toxic reactions were observed. Of these reactions, 33 (37%) fell into the category of headache, depression, ringing of the ears, foul taste in the mouth, etc., none of which could be measured in rats and dogs.1

The foregoing conclusions have important implications for the present-day practice of using animals to test chemicals for safety and effectiveness as drugs in humans. Most of the drugs that reach the market every year are “me too” drugs, namely compounds that differ in minor ways from a prototype drug. This should not come as a surprise, since the animal “models” that are used to screen chemicals are models that responded favorably to the prototype. If Drug X and Drug Y differ only by a minor chemical modification, then they’re likely to have similar biological effects. Not surprisingly, the Food and Drug Administration estimates that only about 3% of the drugs that reach the market are significant medical advances.2
Nobel Prize winner Sir James Black, the pharmacologist who discovered propranolol (Inderal) for treating high blood pressure and cimetidine (Tagamet) for treating ulcers, is a harsh critic of animal models because of species differences.3 Black, who now heads his own research institute in England, believes that drug scientists must work from conceptual models of receptors — the chemical entities to which drugs bind in cells — in order to design fundamentally new drugs.

Certainly the outcome of animal experimentation has been pretty pathetic. Notwithstanding all the pain that has been inflicted on millions of cats, dogs, mice, rats, primates, and other species, the World Health Organization concludes that a mere 200 drugs are medically essential.4 What’s more, animal experimentation has failed to come up with medically essential drugs for major killers like AIDS, cancer, multiple sclerosis and hundreds of other medical horrors.

Pressure from the animal rights movement, coupled with purely pragmatic considerations like those expressed by Black, has led to some changes in drug development. The usual lag time from the test tube to the pharmacist’s shelf used to be about ten years, but the FDA has slashed this to two years for AIDS drugs, mainly by drastically reducing the amount of animal experimentation and getting drugs into clinical (e.g. human) testing much more rapidly. Animal activists have to keep up the pressure for prompt clinical testing of all drugs. Second, we must demand alternatives to preclinical studies using nonhuman animals. Such alternatives are already in use, and include computer simulation and studies of drug-receptor interactions derived from tissue cultures. If we are to have credibility we must demand that experiments be productive and humane; we must demand an end to the old way of screening drugs because it is inefficient and hurtful.

1. Litchfield J.T., Jr: "Evaluation of the safety of new drugs in animals." Clin Pharmacol Ther 3: 665 (1962)
2. PETA Factsheet: "Drug testing: pain, not gain." People for the Ethical Treatment of Animals: Washington, DC (1995), p. 2
3. Bernard L: "Drug design helped little by animal models." Cornell Chronicle, April 23, 1992, p. 3
4. PETA Factsheet, ibid. p. 2

Robert Wilbur is a scientist and researcher. He is also president of the Carriage Horse Strike Force. He lives in New York City.


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