London: An anti-smoking pill that was earlier thought to increase the risk of heart attack and depression is actually safe, researchers say.
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.
The latest research 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.
"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," said professor Daniel Kotz from the medical faculty of the Heinrich-Heine-University Dusseldorf.
Researchers who carried out the study say doctors can prescribe varenicline -- also known as Champix or ChantixTM -- more widely to help people stop smoking.
The team looked at anonymized 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.
Some of them also used nicotine replacement therapy such as patches, chewing gum or lozenges.
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.
"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," added professor Aziz Sheikh, co-director of the University of Edinburgh's Centre for Medical Informatics.
Regulators such as the the US 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, the authors noted.
The study was published in the journal Lancet Respiratory Medicine.