The US Food and Drug Administration (FDA) has issued what the agency terms an “early communication” about a potential, but yet to be confirmed, safety issue with Pfizer’s smoking cessation drug Chantix, where a number of postmarketing cases have reported patients on Chantix experiencing suicidal thoughts and related erratic behaviour.

The information on the cases involved was given to the FDA by the drug maker Pfizer Inc, as part of ongoing post marketing safety monitoring.

An early review of the cases suggests that within days to weeks of starting treatment with Chantix, some patients have had first time experiences of depressed mood, suicidal thoughts, and emotional and behavioral changes.

However, the agency stresses that the role of Chantix in these cases is not clear because:

“Smoking cessation, with or without treatment, is associated with nicotine withdrawal symptoms and has also been associated with the exacerbation of underlying psychiatric illness.”

But, the agency also pointed out that not all the patients in the reported cases had had psychiatric illnesses before taking Chantix and not all had stopped smoking.

Chantix (varenicline) was approved by the FDA last year as a prescription drug to help adults quit smoking. The FDA said on Tuesday 20th November that the early communication reflected the agency’s “current analysis of available data”. It did not mean the agency had concluded that the drug caused the symptoms reported.

The FDA has asked Pfizer for more information about the cases of suicidal ideation (thoughts) and erratic behaviour.

The FDA’s Center for Drug Evaluation and Research will analyse the complete case information, along with a number of recent reports in the popular press and internet sites, and publish its conclusions and recommendations.

In the meantime the agency asks doctors and other health care providers to keep an eye on patients who are taking Chantix, and to look out for mood and behaviour changes in particular. Any patient who is on the drug who notices a change in their mood or behaviour should contact their doctor at once.

The agency also recommends patients be cautious about driving or operating machinery until they have been on Chantix long enough to establish how it affects them, as it can cause drowsiness.

Chantix helps people give up smoking in two ways: it gives the same sense of satisfaction as nicotine and it blocks the effect of nicotine on the brain. The first effect lessens withdrawal symptoms, and the second effect stops nicotine from trigerring the brain’s reward center.

Smoking is the most preventable cause of death in the US, said the FDA last year when it approved the drug.

Director of FDA’s Center for Drug Evaluation and Research, Dr Steven Galson, said at the time the drug was given approval that Chantix was a proven and effective treatment for smokers who wanted to quit.

FDA approval was based on the results of 6 clinical trials involving a total of 3,659 smokers. Two of the trials showed Chantix was better at helping smokers quit than Zyban (bupropion).

A typical course of Chantix lasts 12 weeks, although patients may take it for another 12 weeks if they wish.

Click here for the FDA early communication on Chantix and how to report problems with the drug.

Written by: Catharine Paddock