Long-term paracetamol use could increase the risk of stroke in people with high blood pressure, new research has revealed.
Patients who have a regular 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.
This study, by the University of Edinburgh and funded by the British Heart Foundation, is the first large randomised clinical trial to address this question and complements earlier work in observational studies.
Paracetamol was often suggested as a safer alternative to another class of painkillers called non-steroidal anti-inflammatory drugs (NSAIDs), which are known to increase blood pressure and risk of heart disease.
In the latest study, 110 patients with a history of high blood pressure were prescribed one gram 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 saw 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 around 20 per cent.
The team say 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.
Principal Investigator Professor 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.
“Given the substantial rises in blood pressure seen in some of our patients, there may be a benefit for clinicians to keep a closer eye on blood pressure in people with high blood pressure who newly start paracetamol for chronic pain.”
Professor Sir Nilesh Samani, medical director at the British Heart Foundation, 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.
“However, if you take paracetamol occasionally to manage an isolated headache or very short bouts of pain, these research findings should not cause unnecessary concern.”
