NEW YORK (CNNMoney.com) - GlaxoSmithKline added the increased risk of suicide for young adults to its Paxil label this week, but the antidepressant is past its prime in terms of sales so it's unlikely to hurt the drugmaker.

"If this had happened 7 or 8 years it would have sent the stock down, but Glaxo is trading up today," said Bernstein analyst Gbola Amusa, noting that Paxil no longer has patent protection and Glaxo's protected spin-off, Paxil CR, is declining in sales.

Glaxo's (up $0.11 to $57.10, Research) stock price edged up slightly in afternoon trading.

Glaxo spokeswoman Mary Anne Rhyne said Paxil sales totaled $33 million in 2005 and sales for Paxil CR totaled $209 million. This is a small slice of the British drugmaker's overall sales, which totaled $35 billion in 2005.

Rhyne said that Glaxo conducted a new analysis and revised the label at the request of the Food and Drug Administration. The new data shows 2.19 percent risk of suicidal behavior in adults aged 18 to 24 taking Paxil, compared to 0.92 percent for those on placebo.

Glaxo sent letters to physicians this week informing them of the increased risk.

"This is additional information we thought would be helpful to physicians and their patients," said Rhyne. "We believe, however, that the overall risk-benefit to Paxil remains positive."

Amusa, the Bernstein analyst, said that plaintiffs might sue Glaxo as a result of the new information, but the drugmaker would benefit from the fact that causation is unclear, meaning that it has not been proven that Paxil increases the risk of suicide.

The FDA has taken a hard look at the antidepressant sector, requiring all drugmakers to change their labels in 2004 to reflect reports of suicide risks. In 2005, the FDA ordered the drug makers to provide additional data to fully examine the risk of suicidal thoughts in antidepressant patients.

Other players in the antidepressant industry include Pfizer's (down $0.26 to $24.55, Research) Zoloft, the iconic blockbuster that's slated to lose patent protection in June, 2006, and Wyeth's (up $0.67 to $48.91, Research) Effexor XR, the current market leader with $3.5 billion in 2005 sales.

To read more about the antidepressant industry, click here.

Amusa does not own Glaxo stock.