FDA to review Champix/Chantix side effects

Nov 29 2007

A drug which was designed to help people quit smoking is causing concern following a number of reports that it induces suicidal feelings and aggressive and erratic behaviour.

The drug Champix, which was licensed in the UK last year, is also known as Varenicline and as Chantix in the U.S. and it is causing concern both in the U.S. and Britain.

There have been it seems almost 50 reports to the Medicines and Healthcare products Regulatory Agency (MHRA) in Britain of depression; these have been mainly in patients with a previous psychiatric history, along with another 16 reports of suicidal thoughts.

Between 15,000 and 20,000 people are using the drug in the UK and of the reactions reported to the MHRA, 183 reports were of nausea, 52 reports of abnormal dreams, 49 of dizziness, 37 of fatigue, 82 of headaches, 21 of drowsiness and 67 of vomiting.

The U.S. regulatory body, the Food and Drug Administration (FDA) has also expressed concerns about the drug which is manufactured by drug company Pfizer and are also investigating the drug after receiving similar reports.

Varenicline is novel in that it both stimulates and blocks specific nicotinic receptors in the brain; it is thought that the stimulation of these receptors mimics the effects of nicotine and reduces cravings.

As it also partially blocks the receptor preventing nicotine from binding to it, a weaker response is produced in people who give in to temptation and have a cigarette.

Trials of the drug suggested that it enabled some 44% of smokers to quit; this was on a regime of a dose taken twice a day for 12 weeks where it compared favorably with a placebo and another major anti-smoking drug, bupropion.

The European Medicines Agency also examined some of these concerns in July, and decided then that no action was needed.

Pfizer says there is no scientific evidence establishing a causal relationship between varenicline and the post-marketing report events.

The drug company says quitting smoking, with or without treatment, is associated with nicotine withdrawal symptoms and has also been associated with exacerbating underlying psychiatric illnesses.

The FDA has asked Pfizer for any additional cases of side-effects that it is aware of and is currently reviewing the data; the agency has advised doctors prescribing the drug to monitor patients for behaviour and mood changes.

Champix was licensed by the European Medicines Agency (EMA) in September 2006 and was made available on the NHS.