This past week's presentation on animal ethics made me think about where I stand on the issue. One of the major arguments for testing on animals is that many pharmaceutical and medical discoveries have been made that have saved many lives. Animal testing has allowed for the production of synthetic insulin to be used for patients suffering with diabetes. It has allowed for the production of many antibiotics such as penicillin and vaccines to prevent disease. Even today, animal testing is being used to find a potential cure for cancer, a vaccine for AIDS, a treatment for Parkinson's and a therapy for Alzheimer's. Not only has the effects of animal testing been beneficial to humans but also to animals. Veterinarians have been able to develop treatments for feline Leukemia and Canine distemper through animal testing. The medical and pharmaceutical companies absolutely depend on animal testing to make these advances.
However, are these medical advances just flukes? Merely accidents that happened to work out for the better? In 1999, the FDA approved the use and sale of a drug called Vioxx by the major pharmaceutical giant Merck. Vioxx, an NSAID, is an anti-inflammatory drug that works by removing substances that cause inflammation, pain and fever in the body. It was predominantly used as a treatment for arthritis. In 2004, the drug was taken off the market after it was found that it could double the risk for heart attack and stroke in humans. Vioxx proved safe in all the animal tests prior to its approval by the FDA. For example, in 2002 a test on mice found that Vioxx actually reduced atherosclerosis, build up of fatty substances in arteries, in the animals. These tests led researchers to believe that Vioxx could be used as a safe effective drug, which even prevented heart problems, in humans. Tens of thousands of people suffered related heart attacks and strokes due to Vioxx. Other drugs that have been shown safe in animal tests but have proved dangerous in humans are Fenfluramine, a weight loss drug that thickens heart valves, Baycol, used to lower cholesterol but caused severe muscle toxicity, and Seldane, an allergy medication that was shown to have severe drug interactions. Many of these severe effects were observed in the initial clinical research on humans. However, the companies used the fact that no adverse effects were observed in animal trials to continue marketing these drugs as safe.
It is simple biology; physiological differences between animals and humans make animal testing a poor model for how drugs will interact and what adverse affects might occur in humans. How many more "safe" drugs discovered through animal testing will be marketed only to find out years later that they cause dangerous side effects in humans? How are we to determine whether a medical discovery found through animal testing will be the next insulin or the next Vioxx?