Those with higher blood pressure who routinely take paracetamol may be at a higher risk of suffering from heart disease or strokes, according to new research.
Based on the results of the study, researchers say that people who have been prescribed the painkiller to treat chronic pain should be given the minimum effective dose for the shortest time possible.
As reported by Hull Live, it was previously assumed that paracetamol was safe to take for patients with the condition.
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However, the new findings indicate that paracetamol's effect on blood pressure is akin to non-steroidal anti-inflammatories (NSAIDs) like ibuprofen.
These are known to raise blood pressure and risk of heart disease.
Scientists say the increase in blood pressure may correspond with an approximately 20% higher risk of suffering from heart disease or a stroke.
They have recommended that the results of the study should lead to a review of long-term paracetamol prescriptions to patients — and in particular people with the condition, or those at higher risk of heart disease or stroke.
Personal chairman of clinical pharmacology at the University of Edinburgh Professor James Dear said: “This study clearly shows that paracetamol – the world’s most used drug – increases blood pressure, one of the most important risk factors for heart attacks and strokes.
“Doctors and patients together should consider the risks versus the benefits of long-term paracetamol prescription, especially in patients at risk of cardiovascular disease.”
He added: “In summary, we’ve shown that two weeks of treatment with paracetamol increases blood pressure in patients who have hypertension (high blood pressure).”
Lead investigator Dr Iain MacIntyre, consultant in clinical pharmacology and nephrology at NHS Lothian, said: “This is not about short-term use of paracetamol for headaches or fever, which is, of course, fine – but it does indicate a newly discovered risk for people who take it regularly over the longer term, usually for chronic pain.”
The research found that, after stopping treatment with paracetamol, blood pressure in participants returned to what it was at the beginning of the study — indicating that the drug raised it.
The researchers stated that they do not have accurate figures for the number of people in the UK who are on paracetamol long term and have high blood pressure.
However, it is estimated that around 33% of UK adults have high blood pressure increasing with age, while one in 10 people in Scotland take paracetamol regularly.
In the study, 110 patients with a history of high blood pressure were prescribed 1g of paracetamol four times a day – a dose routinely prescribed for patients with chronic pain – or a placebo for two weeks each.
Researchers found there was a significant increase in the blood pressure of those taking the painkiller, compared with those taking the placebo.
According to the experts, the study was set up to see a very small effect on blood pressure, and they were surprised to see a much bigger impact.
Prof Dear suggested the research indicates the findings could affect a large number of people.
The scientists highlight that a limitation of their study was that it did not look at patients who have chronic pain.
But there is no reason to think that patients who are taking paracetamol for treatment of pain would have a different blood pressure response to the patients in the study, they say.
Professor Sir Nilesh Samani, medical director at the British Heart Foundation, which funded the study, said: “This research shows how quickly regular use of paracetamol can increase blood pressure in people with hypertension who are already at increased risk of heart attacks and strokes.
“It emphasises why doctors and patients should regularly review whether there is an ongoing need to take any medication, even something that may seem relatively harmless like paracetamol, and always weigh up the benefits and risks.”
Dr Richard Francis, head of research at the Stroke Association, said: “High blood pressure is the single biggest risk factor for stroke.
“This new and robust study adds to previous research and suggests regular paracetamol causes blood pressure to quickly increase in people who are already at risk of stroke and heart attacks.
“It’s therefore important that doctors regularly review and weigh up the risks and benefits of prescribing paracetamol.”
Dr Benjamin Ellis, consultant rheumatologist at charity Versus Arthritis, said many people with arthritis and musculoskeletal conditions use paracetamol, or medicines containing paracetamol, to help manage their pain.
He added: “The research demonstrates the need to develop safer medicines to treat pain. It also emphasises the importance of the health services providing more and better options to managing pain other than medicines.
“This includes ensuring that people are supported to be physically active, receive any mental health support they need, and working with charities like Versus Arthritis to provide peer support. If you are concerned about the risks from pain medicines you should speak with a healthcare professional to explore your options.”
