May 12 (Bloomberg) -- GlaxoSmithKline Plc warned doctors that adults under the age of 30 may face an elevated risk of suicide attempts while taking its Paxil antidepressant, extending beyond children the group that may be vulnerable.

A new analysis of data from clinical trials involving almost 15,000 people found suicidal behavior was more likely in adults taking Paxil for depression than in those getting a placebo. The majority of the attempts were in young adults ages 18 to 30. Among older adults taking the drug for any psychiatric disorder, no similar increase was seen.

The analysis is the first from a request by the U.S. Food and Drug Administration for all makers of anti-depression drugs to evaluate whether their medications increased the risk of suicidal thinking or actions among adults. A similar analysis in children led to warnings on drugs including Paxil, Eli Lilly & Co.'s Prozac, Pfizer Inc.'s Zoloft and Wyeth's Effexor in 2004.

``Right now, the warning applies only to kids,'' said Kelly Posner, an assistant professor in the department of child psychiatry at Columbia University Medical Center in New York. ``Later on in the year, whenever the FDA is ready, a large pooled analysis with all the companies and all the drugs will see if they find similar things in the adult data.''

Under Review

The FDA said its review isn't yet complete and all patients taking antidepressants should be carefully monitored for worsening of depression and suicidal thinking. It is essential that patients on Paxil, known in Europe as Seroxat, don't stop taking it suddenly, the agency said in a statement.

``For the vast majority of patients with depression who take Paxil/Seroxat, this medicine helps them to live a normal life,'' said Gwenan Evans, a spokeswoman for London-based Glaxo, in an interview today. ``This new analysis reinforces existing medical guidance to closely monitor patients during treatment. This is especially the case in patients with depression, and the under 30 year olds.''

Doctors reduced the number of antidepressants prescribed for children by 25 percent after the FDA required that drug packaging materials include a warning of suicide risk highlighted in boldface type outlined with a black box, according to Columbia's Posner. Glaxo said it is adding a warning of the risk to young adults that won't be highlighted the same way.

Concerns that antidepressants might trigger suicidal thinking and attempts in children surfaced in 2004 when British regulators issued a warning that children taking Paxil in clinical trials were nearly three times more likely to attempt suicide than those taking placebos. The regulators advised doctors not to use Paxil in children.

Other Suicides

The FDA issued a similar warning nine days later and started its own review of Paxil's pediatric trials. The review soon broadened to include seven other antidepressants. British regulators eventually advised doctors to stop prescribing six antidepressants to children. The FDA warned that children taking antidepressants should be monitored for signs of suicidal thinking.

Suggestions that Paxil can trigger suicidal or violent acts in adults aren't new. A 1991 safety review by an FDA official evaluating the original application for Paxil noted seven completed suicides by adult Paxil patients during clinical trials.

In 2001, a Wyoming jury awarded $6.4 million to the surviving members of the family of Donald Schell, a 60-year-old Wyoming man who killed his wife, daughter, granddaughter and then himself three hours after taking two Paxil tablets given to him as samples by his internist. Lawyers for Glaxo and the family later settled the case.

Paxil Sales

The new review released by GlaxoSmithKline describes one completed suicide among the young adult Paxil patients whose cases it reviewed, a 23-year-old male with social phobia who killed himself in 1997. The clinical investigator conducting the trial determined that the suicide was ``probably unrelated to study medication.''

The FDA is expected to announce a decision on any link to suicidal thoughts in adults in the next few months.

``It adds to what we already know,'' said Dr. Tim Kendall of the Royal College of Psychiatrists in London.

Glaxo in April reported total sales of Paxil, which no longer has market exclusivity, were 161 million pounds ($304 million) in the first quarter. Shares in the drugmaker fell 5 pence to 1,515 pence in London.

Regulators Notified

The higher frequency of suicidal behavior in adults 18 to 24 years old treated with the drug compared with placebo wasn't statistically significant, Glaxo said. There was a statistically significant higher frequency in all adults with major depressive disorder, with eight of 11 attempts involving people ages 18 to 30, the company said.

``It is difficult to conclude a causal relationship'' because of a number of factors, including the small number of incidents involved, the company said in the analysis.

Glaxo said that regulators around the world have been notified of the new data and the company has sent letters to doctors. The FDA and the U.K.'s Medicines and Healthcare Regulatory Agency advised doctors to continue to closely monitor patients taking Paxil.

To contact the reporters on this story: Etain Lavelle in London at at elavelle1@bloomberg.net; Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net.

Last Updated: May 12, 2006 17:33 EDT