Long-term paracetamol use could increase the risk of heart disease and strokes in people with high blood pressure, a study suggests.
Patients who have a long-term prescription for the painkiller, usually used for the treatment of chronic pain, should opt for the lowest effective dose for the shortest possible time, researchers say.
The University of Edinburgh study, published in the scientific journal Circulation, is the first large randomised clinical trial to address the issue and complements earlier work in observational studies.
Paracetamol has often assumed to be a safer alternative to another class of painkillers called non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, which have long been known to increase blood pressure and the risk of heart disease.
In the study, 110 patients with a history of high blood pressure were prescribed 1g of paracetamol four times a day – a routinely prescribed dose in patients with chronic pain – or a matched placebo for two weeks. All patients received both treatments, with the order randomised and blinded.
Those prescribed paracetamol had a significant increase in their blood pressure, compared with those taking the placebo. This rise was similar to that seen with NSAIDs, and might be expected to increase the risk of heart disease or stroke by about 20%, experts say.
The lead investigator, Dr Iain MacIntyre, a 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.”
Prof James Dear, personal chair of clinical pharmacology at Edinburgh, added: “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.”
The study found that after people stopped taking the drug, their blood pressure returned to what it was at the start of the study. Researchers said they did not have accurate numbers of the people in the UK who are on paracetamol long-term and have high blood pressure. But it is estimated that one in three adults in the UK have high blood pressure, increasing with age, while one in 10 people in Scotland – where the research was conducted – take paracetamol regularly.
There were limitations to the study. It involved only 110 people, it did not look at patients with chronic pain, and the results do not reveal anything specific about what might happen in people who did not have high blood pressure to begin with.
Prof Sir Nilesh Samani, the medical director at the British Heart Foundation, which funded the study, said the research showed “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”.
However, he also stressed: “If you take paracetamol occasionally to manage an isolated headache or very short bouts of pain, these research findings should not cause unnecessary concern.”