According to a study, people with high blood pressure who take prescription paracetamol may increase their risk of heart attack and stroke.
Doctors should consider the risks and benefits for patients taking it for several months, according to researchers from the University of Edinburgh.
Taking the painkiller for headaches and fever is safe, they point out.
Other experts say research in more people over a longer period is needed to confirm the findings.
Paracetamol is widely used around the world as a short-term remedy for aches and pains, but also prescribed to manage chronic pain, despite little evidence of its benefits for long-term use.
Half a million people — one in 10 people — in Scotland were prescribed the painkiller in 2018.
If they also have high blood pressure, a condition which affects one in three people in the UK, they may be at higher risk, according to this trial.
He followed 110 volunteers, two-thirds of whom were taking medication for high blood pressure or hypertension.
In a randomized trial, they were asked to take 1g of paracetamol four times a day for two weeks — a common dose for patients with chronic pain — and then dummy pills, or a placebo, for another two weeks.
The trial showed paracetamol raised blood pressure, ‘one of the strongest risk factors for heart attacks and strokes’ — far more so than a placebo, the Edinburgh clinical pharmacologist said , Professor James Dear.
Researchers advise doctors to start patients with chronic pain on as low a dose of paracetamol as possible and to closely monitor those with high blood pressure and at risk for heart disease.
Arthritis is one of the leading causes of chronic pain in the UK. A charity, Versus Arthritis, said safer drugs to treat pain were needed along with other aids, such as mental health support and encouragement to be physically active.
“If you are concerned about the risks of pain medication, you should speak to a healthcare professional to explore your options.” said Dr. Benjamin Ellis, consultant rheumatologist at Versus Arthritis.
Principal investigator Dr Iain MacIntyre, consultant in clinical pharmacology, at NHS Lothian, said: “This is not for short-term use of paracetamol for headache or fever, which is , of course, good.”
Dr Dipender Gill, professor of clinical pharmacology and therapeutics at St George’s, University of London, said the study, published in the journal Circulation, found “a small but significant increase in blood pressure in a white Scottish population “but “many unknowns remain”.
“First, it is unclear whether the observed increase in blood pressure would be maintained with longer-term use of paracetamol,” he said.
“Second, it is unclear whether an increase in blood pressure attributable to paracetamol use would lead to an increased risk of cardiovascular disease.”
A large US study previously found a link between long-term paracetamol use and an increased risk of heart attacks — but it could not prove one caused the other.