Mar. 11, 1999 Tests suggest rats may be more useful than monkeys in some types of drug studies
The recent finding by a researcher at the University of Illinois at Chicago that humans and rats absorb and eliminate some drugs at the same rate may have a dramatic impact on future drug development.
The ability to predict the amount of drug absorption and rate of drug elimination in humans is vital for determining safe and effective dosages. It also may lower the cost of drug development by eliminating the need to test potential drugs on multiple animal species and animals that are more expensive than rats, said the UIC researcher, Win Chiou, professor of pharmacokinetics. He found that people and the rodents absorbed 64 drugs and eliminated 54 drugs at a similar rate.
To satisfy a Food and Drug Administration requirement, pharmaceutical companies generally test new drugs on three to six animal species before conducting human trials. Chiou, a researcher in the UIC College of Pharmacy, said his finding suggests that testing new drugs on rats and one other species may be sufficient.
The similarities in drug absorption and elimination in humans and rats is, he said, "very intriguing." If, for example, the absorption of one of the drugs tested is 20 percent in a rat, it will be close to 20 percent in a human, even though humans weigh up to 300 times as much as rats, Chiou discovered. Human intestines also are up to 10 times bigger and many times longer than rat intestines.
"Monkeys are very similar to humans, but they probably are not as useful for drug absorption studies as rats," Chiou said.
Chiou explained that the basic intestinal structures of rats and humans are similar despite the disparities in length and diameter. He and his team now are comparing drug absorption in humans and rats at multiple intestinal sites. They also are systematically comparing the ability to predict drug absorption and elimination using dogs and other traditional methods. Chiou said that his team's preliminary studies and evaluation of scientific literature indicate that dogs often are poor absorption models for humans.
The FDA and pharmaceutical companies in the United States and abroad have invited Chiou to discuss his findings. Chiou will present his research this fall at the International Pharmaceutical Federation meeting in Barcelona, Spain, and the Southeast Asian-Western Pacific Regional Meeting of Pharmacologists in Taipei, Taiwan.
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