Inamed Corp. narrowly failed to convince a U.S. panel on Tuesday that its silicone breast implants are safe enough to win U.S. approval and end 13-year-old restrictions sparked by concerns over possible illness from leaking silicone.

Shares of Inamed, which had an earlier silicone implant application rejected by the FDA 15 months ago, plummeted by 9.4 percent in after-hours trading.

The advisory committee voted 5-4 against recommending Inamed’s implants, with opponents saying they needed more information on how often and why the devices break.

“I feel that (approval) is premature. I don’t feel secure about the safety,” said Dr. Amy Newburger, a panel member from Dermatology Consultants of Westchester in Scarsdale, New York.

The Food and Drug Administration will consider the advice as it decides whether to lift sales restrictions imposed in 1992 amid concerns that leaking implants could cause long-term, disabling diseases such as lupus or Rheumatoid Arthritis.

Studies have failed to find a connection between silicone implants and chronic illnesses. The implants can cause pain and other local complications, and they can break and require repeat operations to replace them.

“We don’t really know why this device is failing and when it fails,” said Stephen Li, a panel member and president of Medical Device Testing and Innovations.

But “you can never know everything,” countered Dr. Michael Miller, deputy chairman of plastic surgery at the University of Texas M.D. Anderson Cancer Center.

“There are women who will benefit from these implants who don’t have access to them,” he said. Supporters of silicone gel-filled implants tout them as the most natural-looking option.

In the United States, only breast cancer survivors and others needing reconstruction or implant replacements can now receive silicone implants, through clinical trials. Any woman can get breast implants filled with saline.

Dan Cohen, Inamed’s vice president of global government and corporate affairs, said the panel vote was a surprise as the company felt its data was “very strong and very complete.”

Earlier, Cohen told the panel the risks were “acceptably low” and “largely related to the surgical procedure” rather than the device itself. Inamed’s research tracked women with implants for about three years.

In January 2004, the FDA rejected Inamed’s earlier bid to sell silicone breast implants despite a 9-6 vote from another panel that urged approval.

Inamed, which is being bought by Medicis Pharmaceutical Corp., and rival Mentor Corp. have said new silicone implants are more durable, and the gel is stickier and less likely to migrate.

The panel will review and vote on Mentor’s silicone breast implant application on Wednesday.

Piper Jaffray analyst Thomas Gunderson, who rates Inamed “market perform,” said Inamed and Medicis may decide their research dollars could be better spent elsewhere.

“Do you keep beating your head against the wall on one of the most controversial medical devices ever?” he said.

Inamed shares fell to $60.16 on the Inet electronic brokerage in after-hours trade. Mentor fell to $33.80 from a close of $34.56 on the New York Stock Exchange.