Plavix works in men and women, with differences

* Women mostly benefit from reduced heart attack risk

* More gender-based studies urged

By Julie Steenhuysen

CHICAGO, Nov 9 (Reuters) - The popular blood-thinner Plavix prevents heart attacks and strokes in both women and men, but the benefits differ slightly by gender, U.S. researchers said on Monday.

They analyzed data from five major studies of more than 80,000 people, 30 percent of them women, and found that Plavix or clopidogrel cut the risk of having a heart attack or stroke by 16 percent in men and by 7 percent in women.

The study by Dr. Jeffrey Berger of the New York University School of Medicine offers the first look at gender differences with Plavix -- a $9 billion-a-year seller made by Sanofi-Aventis (SASY.PA) and Bristol-Myers Squibb (BMY.N).

Plavix is used widely in treating heart attack patients. It works in a similar way to aspirin by stopping platelets -- tiny blood cells vital for the normal clotting process -- from clumping together and forming life-threatening clots.

In women, the benefit from Plavix mostly comes from a reduction in the risk of heart attacks, but does it not significantly reduce the risk of stroke or death, Berger and colleagues wrote in the Journal of the American College of Cardiology.

In men, Plavix significantly cut the risk of all three -- heart attacks, stroke and death, they said.

The study also found differences in the risk of bleeding, with women who take Plavix in addition to aspirin having roughly twice the bleeding risk as men.

The team said the overall differences in benefit were not statistically significant, and the findings suggest both men and women benefit from taking the drug.

Other studies have shown significant differences in the effects of blood thinners on men and women with heart disease.

Dr. Kirk Garratt of Lenox Hill Hospital in New York, who was not involved in the study, said in a telephone interview that women are traditionally underrepresented in clinical trials, particularly of heart drugs.

"In this analysis, the benefit in women was about about half that seen in men," he said.

Garratt said the study also shows that women have a higher bleeding risk than men that doctors need to watch.

"The risk to benefit (ratio) has gotten narrower for women than it appears to be for men on these drugs," he said.

Garratt said Plavix will soon go generic, but he said the findings may cause drugmakers to work harder to enroll women in studies of new anti-platelet drugs, such as AstraZeneca's (AZN.L) experimental blood-thinning drug Brilinta.

"The hope is that the manufacturers will take this to heart and structure trials that are more oriented toward women," he said.

(Editing by Eric Walsh)