Federal health experts say Yaz and other widely-used birth control pills should carry stronger labeling information that emphasizes recent evidence that the drugs have a slightly higher risk of blood clots than older drugs.

The Food and Drug Administration's panel of experts voted 21-5 Thursday that labeling on the popular drugs made by Bayer is inadequate and should be updated with information from several recent studies.

Yaz, its predecessor Yasmin and related prescriptions use a manmade hormone called drospirenone, which mimics the naturally occurring female hormone progesterone.

Panelists spent more than nine hours discussing often conflicting data on the blood clot risk of drospirenone-containing drugs compared with older medications. While the group disagreed on the quality of the evidence, the overwhelming majority said it should be made more explicit in the label, including the potentially fatal nature of blood clots.

"Clearly the wording is inadequate and incomplete," said Dr. Richard Bockman of New York's Hospital for Special Surgery. "Adverse events have to be made graphic so physicians and patients are aware of the consequences."

In an earlier vote, panelists voted 15-11 that the pills remain a beneficial option for preventing pregnancy. The majority opinion amounts to a vote of confidence that the drugs should remain on the market, though well over a third of panelists voted against the drug's overall benefit, especially given numerous other oral contraceptives available.

"I can see no real group of patients that this drug benefited over existing alternatives," said Mark Woods of New York University School of Medicine. "Without any clear benefit, and given the potentially catastrophic risk, I voted no."

Approved in 2006, Yaz grew into the best-selling birth control pill in the U.S. by 2008, backed by hundreds of millions of dollars in TV and magazine advertising that emphasized its ability to clear up acne and other hormonal side effects. But prescriptions have fallen more than 80 percent in the last two years amid safety concerns and a consumer backlash against misleading advertisements that regulators said overstated the drug's benefits.

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