May 5, 1999
Web posted at: 4:05 p.m. EDT (2005 GMT)

In this story: Drug metabolism enzymes work differently in men and women Companies hesitate to test drugs on women of childbearing age RELATED STORIES, SITES

WASHINGTON (CNN) - Women are more likely than men to suffer side effects from some drugs, according to research presented Wednesday at a meeting sponsored by the National Institutes of Health (NIH) and the U.S. Food and Drug Administration.

At the conference, cardiologist Raymond Woosley, chairman of the Department of Pharmacology at Georgetown University Medical Center, said his research shows that nearly 40 drugs could be more likely to cause sometimes fatal heart problems in women than in men.

He said the drugs include antibiotics and medicines used to treat heart disease. For some of the drugs, women are twice as likely to suffer serious reactions. For others, the differences between men and women are less dramatic.

Much of the research has been on animals or is in the preliminary stages in humans, and doctors said more studies need to be done.

Drug metabolism enzymes work differently in men and women

Other studies presented showed that specific enzymes involved in drug metabolism work differently in men and women, and that men and women respond differently to pain medications.

"We need to understand the biology, what it is about men and women that is causing this," said Woosley.

He said it appears that body size and hormones are two major factors.

"When I was in medical school, I was told the heart was a muscle and the same in men and in women. We didn't know that hormones make the heart function," he said.

Companies hesitate to test drugs on women of childbearing age

New drugs are always tested on both men and women, according to Dr. Bert Spilker, senior vice president for scientific and regulatory affairs for the Pharmaceutical Research and Manufacturers of America.

Gender differences in drug metabolism in animals or in humans in the laboratory do not necessarily make a significant difference in actual patients, he said.

Pharmaceutical companies are beginning to enroll more women, Woosley said. But they need to consider whether the women are post-menopausal, on oral contraceptives, or in their menstrual cycles when taking the drugs, he said.

Dr. Vivian Pinn, director of the NIH's office of research on women's health, is concerned that drug companies hesitate to include women of childbearing age in their drug studies for fear that the drugs could harm the fetuses. She said it's difficult, but companies need to find ways to do research on women of childbearing age.

"We've got a real desire on the part of women to know more, especially women who are pregnant or want to become pregnant," Pinn said.