BELTSVILLE, Md. – Pfizer Inc said its epilepsy drugs do not increase the risk of suicidal behavior and should be exempt from tougher warnings being sought for similar medications, despite concerns from U.S. health regulators.

The company told a Food and Drug Administration advisory panel Thursday that its Lyrica and Neurontin drugs work differently than those of rivals.

A company review of available data showed they were not linked to higher rates of completed suicides or related thoughts, Pfizer told the FDA meeting of outside experts.

“There is no evidence of an elevated risk,” said Christopher Wohlberg, Pfizer's team leader for Lyrica.

The FDA is seeking the advisory panel's advice on whether a strong “black box” warning should be required for 11 drugs that treat seizure disorders or for only some of them.

FDA officials told the panel that their analysis found a clear link between most of the drugs and greater suicidal behavior and there was no reason to exclude certain medicines.

The issue is particularly complicated because suicidal behavior can be a symptom of epilepsy, a condition in which abnormal electrical activity in the brain triggers seizures that can cause involuntary movement or behavior.

Epilepsy medications aim to prevent seizures, and roughly 11 million patients take them, according to data from the FDA.

Some epilepsy drugs already caution about possible suicide, but a boxed warning – the strongest in the United States – could dent sales as black boxes must be prominently displayed in advertising and could make doctors more cautious about prescribing the drugs.

If Pfizer were to avoid a boxed warning, it could more freely market its medicines. Abbott Laboratories Inc's Depakote already has a boxed warning for liver damage and other complications.

Other epilepsy drugs include GlaxoSmithKline Plc's Lamictal , Johnson & Johnson's Topamax and UCB Inc's Keppra, among others.

The medications brought in more than $10 billion in 2007 sales, according to healthcare information company IMS Health. Both Lamictal and Topamax saw roughly $2.1 billion in sales, while Lyrica reached nearly $1.1 billion and Keppra $1 billion.

Similar suicide warnings have been added in recent years to drugs for depression. Some panel members expressed concerns about the effect those cautions had on patients, noting that prescriptions have declined.

“What we saw ... was a real scare factor,” said Gail Griffith, a consumer representative on the panel.

FDA officials said it was too early to see what impact the depression drug warnings had on related suicides but boxed warnings are meant draw attention to risks, not deter use.

For epilepsy products, FDA Director of Neurology Products Russell Katz told the advisers that while it was unclear how the various epilepsy drugs worked, they treat the same condition and should be considered as a group.

“It is important that we avoid inappropriately shifting prescribing to members of the class that in fact have the same signal,” Katz told the panel.

While Pfizer said their drugs were unique and should be weighed separately, one of its rivals agreed with the FDA.

Jack Modell, Glaxo's vice president of clinical development for neurosciences, said available data was difficult to interpret, but Glaxo's analysis mirrored the FDA's findings and warnings should be included on all such drugs.

A number of doctors and researchers expressed concern to the panel about the possible new warnings, saying current data was not conclusive.

But lawyers and family members for those who took some of the epilepsy drugs in question and committed suicide, said companies and the FDA should have done more sooner to warn the public.

Shares of Pfizer were unchanged at $18.03 in afternoon trading. Shares of Glaxo were down 1 percent to $48.07, while shares of Johnson & Johnson were up 1.1 percent to $66.93. Shares of Abbott were up 0.3 percent to $57.09. All four companies trade of the New York Stock Exchange.

(Reporting by Susan Heavey; Editing by Tim Dobbyn)