Despite earlier health agency warnings, there is no strong evidence that the anti-smoking drug Chantix raises the risk of suicidal thoughts or depression compared to other stop-smoking products, researchers reported Thursday in the British Medical Journal.

Back in July of this year, U.S. health officials ordered strong black box warnings be added to Chantix (also called varenicline) as well as anti-smoking drug Zyban, following more than five thousand reports of depression, hostility and other behavioral changes possibly associated with use of these drugs.

There have been recent concerns that varenicline, a relatively new smoking cessation product, may increase the risk of suicidal behavior and suicide, study co-author Dr. David Gunnell of the University of Bristol, UK, explained in an email to Reuters Health.

We found no clear evidence of an increased risk of self-harm or depression associated with varenicline, he said.

The findings stem from data on more than 80,660 would-be quitters in the UK who used different smoking cessation products between September 2006 and May 2008.

A total of 63,265 of these individuals used nicotine replacement products, 10,973 used Chantix, and 6,422 used Zyban, an antidepressant also called bupropion, which has been found to help smokers quit.

When researchers looked at medical records, they didn't find any evidence of an increased risk of serious mental health problems (i.e., self-harm, suicidal thoughts or depression) while they were using these products and during the three months after the last prescription was filled.

Gunnell cautioned, however, that based on the size of the study, it's still possible that Chantix does increase the risk of suicide - or even decrease it.

Other studies should be undertaken to provide further evidence on this issue, he concluded.

The study was funded by a grant from the UK's Medicines and Healthcare Products Regulatory Agency (MHRA).

SOURCE: British Medical Journal, online October 2, 2009.

United kingdom Medicine