Anti-smoking drug linked to 10 British suicides

The MHRA says the number of users reporting adverse side effects while using Champix, also known by its generic name varenicline, has doubled in the past seven months - up from 1,811 in February to 3,541 in September.

The figures are on the MHRA's website, which holds regularly updated information about the reported effects of drugs licensed for use in the UK. The information is provided by doctors, nurses and patients.

The watchdog is now warning doctors and nurses to monitor the effects of the drug on smokers over the New Year, when many will try to kick the habit.

Its latest bulletin states: 'We continue to receive reports of suspected adverse reactions associated with varenicline, the most frequently reported of which are psychiatric disorders. As Christmas and the time for New Year's resolutions approach, we remind you to highlight to those taking varenicline the possibility of adverse psychiatric effects.'

Champix quit-smoking drug

Karen McGhee says Champix caused her to attempt suicide

Last April an inquest heard how TV producer Omer Jama, 39, slashed his wrists eight weeks after starting a course of pills. A toxicologist told the hearing: 'There is a possibility he could have been influenced by the side-effects of the drug.'

In November 2007, father of two Wayne Marshall, 36, from Doncaster, was found hanged shortly after completing a 13-week course of Champix.

Karen McGhee, 38, from Greenock in Scotland, tried to hang herself following a course of the drug. She said: 'I don't have any doubt Champix is what caused me to try to take my own life.'

Bob Rappaport, of the US Food and Drug Administration's drug-evaluation centre, has said: 'A number of compelling cases look like they are the result of exposure to the drug itself and not other causes.'

Earlier this year all pilots and air traffic controllers in the US were banned from taking the drug because of fears about potential side effects.

Champix was launched in the UK in 2006. It works on the brain's receptors to reduce the cravings and withdrawal symptoms associated with quitting.

In trials, nearly a quarter of those taking Champix had given up smoking after a year compared with 16 per cent using nicotine patches.

But after monitoring adverse effects, the European Medicines Agency ruled last December that the safety leaflets in boxes of Champix be updated to include warnings about suicide and depression.

Manufacturer Pfizer added the warnings in February and updated them in July. It advises patients who suspect they are experiencing side effects to stop taking the medication.

Pfizer said: 'Stopping smoking, with or without treatment, is associated with nicotine withdrawal symptoms and the exacerbation of underlying psychiatric illness.

'Pfizer rigorously tested varenicline in a comprehensive clinical trial programme lasting many years and involving thousands of patients.

'Based on the results of those clinical trials, regulatory agencies in Europe, the US and elsewhere have recognised the safety and efficacy profile of varenicline and approved the medicine for use in smoking cessation in adults.'

The MHRA confirmed the figures on its website were accurate. A spokesman said: 'The side effects [of Champix] may have gone up but the number of people on it may have gone up too, so it would be useful to know the number of prescriptions that have been written.'