Animal Experimentation - Frequently Asked Questions
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Animal Experimentation - Frequently Asked Questions

How can we know that medications will not cause birth defects without testing them on animals?

A principle called Karnofsky's Law states that any substance can be teratogenic (cause birth defects) if given to the right species, at the right stage in development, in the right dose. Even common table salt and water are teratogens in some species if given at a vulnerable time in ample enough amount. In other words, all medications can cause birth defects in some creature. An immense amount of experimentation supports this rule.

Data also supports the fact that not all species are equally susceptible to teratogenic influences by any given chemical. Likewise, an agent that is teratogenic in some species may have little or no teratogenic effect in others. According to a respected treatise on birth defects, "because substances cross the placental membrane by a number of mechanisms, some differences in species reactivity to teratogens may be due to accessibility of the drug to the embryo." Of over 1,200 tested chemicals that cause birth defects in animals, only thirty cause them in humans, according to the New England Journal of Medicine. Articles in many other publications repeat these conclusions.

Many safe and useful drugs have been shown to cause birth defects in lab animals:

  • Lovastatin
  • Chondroitin sulfate
  • Acetazolamide
  • Dichlorphenamide
  • Ethoxzolamide
  • Methazolamide
  • Furosemide
  • Clonidine
  • Diazoxide
  • Hydralazine
  • Reserpine
  • Guanabenz
  • Diltiazem
  • Nifedipine
  • Codeine
  • Hydrocodone
  • Hydromorphone
  • Meperidine (Demerol)
  • Morphine,
  • Oxymorphone
  • Phenazocine
  • Propoxyphene
  • Colchicine
  • Allopurinol
  • Aspirin
  • Acetaminophen
  • Other non-steroidal anti-inflammatory drugs
  • Enflurane
  • Ether
  • Halothane
  • Isoflurane
  • Nitrous oxide
  • Sevoflurane
  • Procaine
  • Corticosteroids
  • Ampicillin
  • Cephalothin
  • Chloramphenicol
  • Erythromycin
  • Many antibiotics, antifungal medications and antiviral medications
  • Antiparasitics
  • Anthelmintics
  • Antimalarials
  • Anti-hyperglycemics
  • Insulin
  • Thyroxine
  • Triiodothyroacetic acid
  • Methylthiouracil
  • Propylthiouracil
  • Aminophylline

Most of the medications used to treat nausea and vomiting, allergic conditions, and respiratory ailments cause birth defects in animals, but not humans.

After epidemiology or clinical observation links drugs to birth defects, animals can usually, though not always, be found to demonstrate that effect. Researchers have not been successful in reproducing birth defects in other animals for the following drugs that are teratogenic in humans: Captopril, Enalapril, Minoxidil, some calcium channel blockers, or Warfarin.

The popular lab animal, the rat, has been shown to get birth defects from almost every chemical that causes birth defects in humans. This is meaningless though. If chemicals that harm rat offspring do not cause birth defects in humans, the rat tests are not predictive.

What is teratogenicity testing good for and why does it continue? As Dr. Hawkins, professor of Obstetrics, pointed out,

The great majority of perinatal toxicological studies seems to be intended to convey medico-legal protection to the pharmaceutical houses and political protection to the official regulatory bodies, rather than produce information that might be of value in human therapeutics.Just as Karnofsky postulated, if researchers try hard enough they may eventually inflict birth defects on some animal species with a substance that is teratogenic in humans. But to what purpose? Animal experiments that are not predictive are of no value. They just use up money that might otherwise fund research of real medical value. There is no sense in "validating" something that is already known from human data.

Go on to Didn't all winners of the Nobel Prize in Medicine and Physiology experiment on animals?
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