The Food and Drug Administration will require two smoking-cessation drugs, Chantix – blamed by friends and family of a Dallas musician for the violent behavior that led to his death in 2007 – and Zyban, to carry the agency's strongest safety warning over side effects including depression and suicidal thoughts.

The new requirement, called a "black box" warning, is based on reports of people experiencing unusual changes in behavior, becoming depressed, or having suicidal thoughts while taking the drugs.

The antidepressant Wellbutrin, which has the same active ingredient as GlaxoSmithKline PLC's Zyban, already carries such a warning.

The FDA is also requiring an additional study on Chantix and Zyban to determine the extent of the side effects.

Pfizer Inc., which makes Chantix, had already updated its labeling after the FDA began investigating potential side effects in 2007.

That investigation was sparked by reports of about 37 suicides and more than 400 of suicidal behavior in connection with the drug.

The FDA announced that investigation after the death of Carter Albrecht, 34, in Dallas in September 2007. His girlfriend told police that Albrecht suddenly became violent, had hit and chased her into her house and then was attempting to break into the home of her next-door neighbor in the White Rock Lake area when he was shot. Police said the homeowner shot once at the top of the door to scare Albrecht away but instead struck the 6-foot-4 musician in the head, killing him.

Albrecht, who played guitar and keyboard for the bands Sorta and Edie Brickell & New Bohemians, had a blood alcohol level of 0.29 when he died, according to an autopsy report. The legal limit for driving is 0.08.

After his death, the FDA asked Pfizer to provide reports of any "adverse events similar to the events that occurred with Mr. Albrecht."

Albrecht's girlfriend, Ryann Rathbone, said she and Albrecht had been taking Chantix for about a week before he died, and she said they were having vivid sleep experiences that users call "Chantix dreams."

In February 2008, the FDA said the connection between Chantix and serious psychiatric problems was increasingly likely, though the company had already updated the label to reflect the potential side effects.

Despite the new, stricter warnings, the FDA said consumers and doctors still have to weigh the benefit versus the risks when taking the drug.

"The risk of serious adverse events while taking these products must be weighed against the significant health benefits of quitting smoking," said Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research. "Smoking is the leading cause of preventable disease, disability, and death in the United States, and we know these products are effective aids in helping people quit."

Last fall, the FDA also began looking into scores of patient reports about blackouts and injuries while taking Chantix. The Federal Aviation Administration later banned use of Chantix by pilots and air traffic controllers. The drug's label also warns that patients may be too impaired to drive or operate heavy machinery.

Chantix was approved in 2006. Sales reached $846 million in 2008, a 4 percent drop from the prior year, as concerns over side effects surfaced.

"The labeling update underscores the important role of health care providers in treating smokers attempting to quit and provides specific information about Chantix and instructions that physicians and patients should follow closely," said Dr. Briggs W. Morrison, senior vice president of the primary care development group at Pfizer.

Pfizer said it made the revised label warnings in agreement with the FDA and is immediately making the information available to health care providers and patients.

The Associated Press,

The Dallas Morning News