WASHINGTON－Medical researchers have uncovered a startling and disturbing fact: Many prescription drugs seem to work very differently in women from the way they do in men.

Scientists still do not know why－hormones, weight and metabolism are among the chief suspects. Whatever the causes, researchers are convinced that understanding the differences between how men and women respond to drugs holds the key to new knowledge and safer medicines for everyone.

“That’s really the core－ by unlocking these kinds of scientific gender mysteries, we can apply them to developing medications that are safe and that work in all individuals,” said Marietta Anthony, an official with the women’s research program at the US National Institutes of Health(NIH). “For the first time, we are documenting that men and women respond differently to drugs and sometimes with serious consequences, including death.”

The NIH last month convened a two-day meeting on the topic so scientists could compare notes and discuss future research. And in the last year, since the Food and Drug Administration (FDA) started requiring companies to conduct gender studies on all applications for new drugs, the field has begun to heat up.

Lessons about the baffling gender differences have come the hard way from recent experiences with experimental drugs and, tragically in some cases, from drugs already on the market.

One experimental drug, for example, which at first seemed a perfect antidote for a rare form of stroke, worked spectacularly in men－ and not at all in women. Eventually it was approved for sale in several European countries－ but only for use in men. And it still is not on the market in the US.

Another drug－ the once-popular allergy medication Seldane, which was removed from the market in 1997－ was found to cause life-threatening cardiac arrhythmias and in some cases resulted in death when taken with certain other drugs.

Looking at the data, experts discovered that these heart problems were striking women twice as often as men.

“We missed it at first,” said Dr Raymond L. Woosley, chairman of the pharmacology department at Georgetown University in Washington. “It look a while before it became clear. But then we realized this is too much to be coincidence. There has to be a biologic basis for this.”

The new research on gender differences could have a significant impact on the way physicians prescribe drugs－ identifying vulnerable women and protecting them from dangerous side effects.

21st century