Pfizer, Glaxo anti-smoking drugs need warning - FDA

WASHINGTON (Reuters) - U.S. health officials said on Wednesday they ordered Pfizer Inc and GlaxoSmithKline PLC to add strong "black box" warnings on smoking cessation drugs to highlight a risk of serious mental health problems including suicidal thoughts.

The warnings must be added to Pfizer's Chantix and Glaxo's Zyban, the Food and Drug Administration said in a statement.

"The warning will highlight the risk of serious mental health events including changes in behavior, depressed mood, hostility, and suicidal thoughts when taking these drugs," an FDA statement said.

Pfizer said it had added the warning to the prescribing instructions for Chantix. "The benefits of Chantix outweigh the risks for many patients when used as directed," said Dr. Briggs Morrison, a senior vice president at Pfizer.

GlaxoSmithKline officials were not immediately available for comment.

Pfizer shares fell 1.2 percent to $14.82 early Wednesday afternoon on the New York Stock Exchange. Glaxo shares gained 2.3 percent to $36.15, also on the NYSE.