Popular nicotine mints used to help smokers quit may trigger a heart rhythm problem that can increase the risk of stroke, drug watchdogs have warned.

The list of potential side effects of Nicotinell's Mint Compressed Lozenges has been updated to include atrial fibrillation, a condition that can cause a rapid and intense heartbeat and lead to life-threatening complications.

It applies to the brand's 1mg and 2mg lozenges, which are sold at high-street staples including Boots, Tesco, Morrisons and ASDA, costing £24 for a pack of 204.

Nicotinell's lozenges, which have the appearance of a small, white tablet, are widely used by those who want to quit smoking.

As they dissolve in the mouth, the lozenges release nicotine - the highly addictive stimulant found in cigarettes and vapes - into the bloodstream.

Research has long shown that nicotine can increase heart rate, including a previous study published in the journal Nicotine and Tobacco Research that looked at the effect of lozenges.

Another study in the European Heart Journal, published last December, said nicotine makes the heart work harder by triggering the body's 'fight or flight' response, causing it to beat faster and pump more forcefully.

According to the British Heart Foundation (BHF), people with atrial fibrillation are five times more likely to have a deadly or life-changing stroke.

Stroke is one of the leading causes of death in the UK, killing around 38,000 Britons per year. 

Nicotinell's guidance says the likelihood of atrial fibrillation occurring from its products is 'not known'. 

It now sits alongside other potential side effects in the 'not known' group like tremors – the term for uncontrollable shaking – as well as flu-like symptoms and itchy hives. 

However, the most common side effects of the lozenges include nausea, mouth and throat pain, vomiting, diarrhoea, stomach pain, dizziness and insomnia. 

The NHS urges anyone who believes they may have atrial fibrillation to see a GP.

Alongside an irregular or rapid heartbeat symptoms can include feeling extremely tired and suffering with chest pains.

People with the condition may also find it harder to exercise alongside having a shortness of breath or feeling faint. 

According to the BHF, around 1.5 million people have been diagnosed with atrial fibrillation in the UK.

That is a 50 per cent jump from 2013, when around one million people had the condition. 

The charity also estimated that 270,000 people in the UK may have atrial fibrillation without knowing it.

Professor Sir Nilesh Samani, BHF medical director, said previously that the figures showed an 'astonishing rise' in the number of people diagnosed with the condition.

He added: 'Research has helped us understand the links between atrial fibrillation and stroke and that has spurred the efforts we have seen in recent years to identify people with this potentially dangerous heart rhythm.

'What remains troubling is the sheer number of people who are undiagnosed and unaware that they are living with a heightened risk of stroke. Finding people with this hidden threat must remain a priority.'

A Danish study, published in the British Medical Journal in 2024, also found that around 40 per cent of people with atrial fibrillation are likely to develop heart failure during their lifetime. 

By comparison, the researchers estimated that around 20 per cent would experience a stroke.

Heart failure occurs when the heart is unable to pump blood around the body effectively. 

It is one of several cardiovascular diseases, which collectively kill around 170,000 people in the UK each year.