© Pfizer
Champix by Pfizer: "Because we care"
Fears are growing over the safety of an anti-smoking "wonder drug", taken by nearly a quarter of a million Britons, after officials in America linked it to 37 suicides.

The Food and Drug Administration said it looks "increasingly likely" that there is a connection between the drug Champix and serious psychiatric problems.

The Mail on Sunday revealed in December that there were concerns over the drug after it emerged that seven deaths in Britain were thought to be linked to the pill.

But updated figures now suggest that 11 people taking Champix in the UK have died.

And reports of suspected adverse reactions to the drug to the Government's medicines watchdog, the Medicines and Healthcare Products Regulatory Agency, have risen by 35 per cent to 1,811 in just the past seven weeks.

The FDA began investigating Champix in November after a number of patients reported possible side-effects ranging from depression and agitation to headaches and nausea.

On top of the 37 suicides, it has recorded more than 400 cases of suicidal behaviour.

Manufacturer Pfizer has insisted a direct link between Champix and psychiatric problems has not been officially established and that nicotine withdrawal can lead to mood swings and behavioural changes.

But the FDA said it had found evidence that people taking Champix developed problems even if they were still smoking.

Bob Rappaport, a director at the FDA's drug-evaluation centre, said: "A number of compelling cases look like they are the result of exposure to the drug itself and not other causes."

Champix, which is marketed as Chantix in the US, was launched in Britain in December 2006 and touted as the most effective weapon in the fight to give up smoking.

In trials, 22.5 per cent of those who took the prescription-only drug were still not smoking after a year, compared with 16 per cent who used nicotine replacement therapy and three per cent relying on willpower.

The non-nicotine product works on brain receptors to relieve the cravings and withdrawal symptoms associated with giving up smoking.

The European Medicines Agency that licenses Champix has ordered a safety warning to be included in patient information.

It said that any users who develop suicidal thoughts should stop their treatment and contact their doctor, but there were no plans to ban the drug.

A spokeswoman for Pfizer said: "Clinicians should be aware of the possible emergence of depressive symptoms in patients undergoing a smoking cessation attempt, with or without pharmacological treatment, and should advise patients accordingly. Our priority is patient safety."