A highly effective drug that helps smokers to quit does not increase their risk of heart attack and depression as was previously thought, research suggests.
Researchers who carried out the study say doctors can prescribe varenicline - also known as Champix™ or ChantixTM - more widely to help people stop smoking.
Varenicline is the most effective medication to help smokers quit but previous reports have suggested that users may be more likely to suffer a heart attack.
The drug has also been linked to depression, self-harm and suicide.
This latest research - which has for the first time simultaneously studied these potential side effects - supports recent studies that failed to find any evidence that varenicline has a negative effect on mental health. It also shows that taking the drug does not raise a person's risk of heart disease.
The team looked at anonymised health information from more than 150,000 smokers across England.
The patients had been prescribed either varenicline or another anti-smoking drug called bupropion to help them quit, or had used nicotine replacement therapy - such as patches, chewing gum or lozenges.
They were tracked for six months to assess any impact of the treatment on their health.
Researchers found that people taking either varenicline or buproprion were no more likely to suffer a heart attack than those using nicotine replacement therapy.
People were also not at higher risk of depression or self-harm, researchers say.
The study was led by researchers from the Universities of Edinburgh and Dusseldorf and is published in The Lancet Respiratory Medicine. Researchers at Maastricht University, University College London and Harvard Medical School also contributed to the study. Data were provided by QResearch.
Professor Daniel Kotz, from the Medical Faculty of the Heinrich-Heine-University Dusseldorf, said: "Smokers typically lose three months of life expectancy for every year of continued smoking. Our research supports the use of varenicline as an effective and safe tool to help people quit."
Professor Aziz Sheikh, Co-Director of the University of Edinburgh's Centre for Medical Informatics, said: "On the basis of our extensive analysis, we believe it is highly unlikely that varenicline has any significant adverse effects on cardiac or mental health. Regulators such as the United States Food and Drug Administration (FDA) should review its safety warning in relation to varenicline as this may be unnecessarily limiting access to this effective smoking cessation aid."