New birth defects study - animal tests accurate half the time


Unborn children at risk of birth defects

WASHINGTON--Pregnant women may unknowingly be putting their unborn children at risk of birth defects by taking over-the-counter medications and prescription drugs, and using common household chemicals, according to a new study published in the May issue of the research journal, Biogenic Amines.

"The Future of Teratology Is In Vitro" shows that many common drugs and household chemicals have been certified as safe for humans on the basis of animal tests that are accurate on average slightly more than half the time.

"We are betting the health of our children on odds just slightly better than a coin flip," said principal author Jarrod Bailey, Ph.D., project development coordinator at the University of Newcastle Upon Tyne School of Population and Health Sciences.

Potential teratogens--drugs and chemicals that can cause birth defects during pregnancy--are tested on animals, including mice, rabbits, dogs, and monkeys. None of these animal tests can accurately predict how the substances will affect humans, said Dr. Bailey. "There are simply too many differences in physiology and biochemistry," he noted.

As a result, researchers test drugs and compounds across a wide spectrum of species, a practice that leads to conflicting and often useless results. Among the examples cited: Cortisone has teratogenic effects on every animal species tested, but none in humans. Valium can cause fetal malformations in humans during the first trimester of pregnancy, but causes none in rats.

According to the report's authors, "Virtually all known human teratogens have so far been identified in spite of, rather than because of, animal-based methods."

The answer, said Bailey, is in vitro, or test-tube based, technology. "Embryonic stem cell tests (EST) are more effective in detecting potential embryotoxicities than tests using animals," he said.

"It is time to admit that animal-based testing is an abject failure," Bailey added. "An estimated 50,000 to 70,000 new chemicals and up to 400 new drugs are introduced to the market every year. Every year we delay, every year we continue to rely on animal testing, brings us that much closer to another tragedy like thalidomide."

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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