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Study: Long-Term Paracetamol Use Raises Blood Pressure

Paracetamol has often been cited as a safer alternative to non-steroidal anti-inflammatory drugs (NSAIDs) with regards blood pressure and cardiovascular health. But now researchers have raised concerns about this, suggesting that those taking paracetamol long-term may be at greater risk of heart attack and stroke.

In the first large randomised clinical trial to address whether paracetamol has an effect on blood pressure, researchers from University of Edinburgh performed a double-blind, placebo-controlled, cross-over study with 110 individuals, all of whom had hypertension.

The participants were randomised to receive 1g paracetamol four times a day or matched placebo for 2 weeks, followed by a 2-week washout period, before crossing over to the alternate treatment. Researchers measured 24-hour ambulatory blood pressure at the beginning and end of each treatment period, with the primary outcome of the study being comparison of the change in mean daytime systolic BP from baseline to end of treatment between the placebo and paracetamol arms.

Long-term Paracetamol Use Should Prompt a Closer Eye on Blood Pressure

In their study, published in the scientific journal Circulation, the researchers found that those prescribed paracetamol saw a significant increase in their systolic blood pressure of around 5 mmHg, compared with those taking the placebo. They commented that "the rise in blood pressure was similar to that seen with NSAIDs and might be expected to increase the risk of heart disease or stroke by around 20%".

Prof James Dear, personal chair of Clinical Pharmacology at the University of Edinburgh, 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." 

He added that, together, patients and their doctors should "consider the risks versus the benefits of long-term paracetamol prescription", particularly those patients at risk of cardiovascular disease.

Principal Investigator Prof David Webb, chair of Therapeutics and Clinical Pharmacology at the University of Edinburgh, said: "We would recommend that clinicians start with a low dose of paracetamol, and increase the dose in stages, going no higher than needed to control pain." 

He went on to caution that the substantial rises in blood pressure demonstrated might prompt doctors to "keep a closer eye on blood pressure in people with high blood pressure who newly start paracetamol for chronic pain".

Study Raises Many Questions

Prof Kevin McConway, emeritus professor of Applied Statistics, The Open University, explained to the Science Media Centre how: "All the patients already had hypertension," meaning that the trial “cannot directly give information on whether taking paracetamol in these doses would increase blood pressure in people who did not already have hypertension."

"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", said Prof Sir Nilesh Samani, medical director at the British Heart Foundation, who funded the study. "It emphasises why doctors and patients should regularly review whether there is an ongoing need to take any medication."

Dr Dipender Gill, NIHR clinical lecturer in Clinical Pharmacology and Therapeutics, St George’s, University of London, emphasised how there were still many unknowns. He told the Science Media Centre how it was not clear whether the increase in blood pressure would be "sustained with longer term use of paracetamol", and also it was not known "whether any increase in blood pressure attributable to paracetamol use would lead to an increased risk of cardiovascular disease".

Prof Kevin McConway raised the point that, as all the participants came from Scotland and were all Caucasian, there’s "no direct evidence that things would be the same in other places or ethnic groups", an observation that was echoed by Dr Gill.

The research team says the findings should lead to a review of long-term paracetamol prescriptions to patients – particularly those with high blood pressure, or those at particular risk of heart disease or stroke.

Commenting on the study to the Science Media Centre, Dr Richard Francis, head of research, Stroke Association, said: "Patients in this study had pre-existing high blood pressure, so further studies in people with normal healthy blood pressure, over longer time periods are needed to confirm the risks and benefits of using paracetamol more widely."

Lead Investigator for the study, Dr Iain MacIntyre, consultant in Clinical Pharmacology and Nephrology at NHS Lothian, offered reassurance saying: "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."

Lead Image Credit: Ginasanders/Dreamstime


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