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By Susan Heavey

WASHINGTON, Feb 6 (Reuters) - Some newer birth control pills, which carry twice the risk of dangerous blood clots as older contraceptives, should be banned, an advocacy group said in a petition filed with U.S. regulators on Tuesday.

The pills, which include several made by Barr Pharmaceuticals Inc. <BRL.N> and Akzo Nobel NV <AKZO.AS> unit Organon BioSciences, are also no better than some older ones, Public Citizen said in a petition filed with the Food and Drug Administration.

Its Health Research Group estimated that in the year ended last October, more than 7.5 million prescriptions were filled for such pills, which also include's Johnson & Johnson's <JNJ.N> Ortho-Cept and Watson Pharmaceuticals Inc.'s <WPI.N> Reclipsen.

The petition also targeted Barr's Mircette, Velivet, Kariva and Apri-28, as well as Organon's Desogen. Generic contraceptives containing desogestrel were also cited.

Older oral contraceptives contain estrogen and progestin hormones. But newer ones sold in the United States -- so-called "third generation" -- contain a different type of progestin called desogestrel.

"By banning third-generation oral contraceptives, the FDA will potentially save hundreds of young women a year from developing venous thrombosis and its disabling and sometimes fatal consequences," the group wrote.

FDA spokeswoman Susan Cruzan said the agency had received the petition and would review it carefully.

Blood clots are a known risk of hormonal contraceptives, including birth control pills. They can occur throughout the body and dislodge to block blood flow to the lungs and other crucial organs.

The FDA publicly announced the higher blood clot risk in 1995, and newer pills also contain a warning about the risk.

But Public Citizen said its analysis of available research found pills with desogestrel still too risky to be sold.

"Since there is no evidence of any superior clinical benefit, it is impossible to recommend that third-generation oral contraceptives remain on the market when second-generation oral contraceptives are equally effective and do not cause an increased risk of blood clots," the petition said.

Representatives for the makers of the pills either had no immediate comment or did not immediately return calls seeking comment.

In late-morning trade on the New York Stock Exchange, shares of Barr were off more than 1 percent, or 60 cents, at $53.13, while J&J shares were down less than 1 percent, or 29 cents, at $66.01. Watson shares were up less than 1 percent, or 15 cents, at $27.71.

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