The Doctor’s Surgery

Should you keep on taking the tablets?

Paracetamol might raise blood pressure – but remember the benefits theodore dalrymple

The problem with medical research is that it’s always finding things for us, whether we be patient or doctor, to worry about – especially in an age of hypochondria like ours.

Just as we think that something is nice and safe, research shows that it isn’t, or at least might not be.

For example, what could be safer than good old paracetamol – apart from when you take it in overdose, as about 80,000 people do in England and Wales each year. At the last count, 235 of them died – a quarter of all who died by self-poisoning.

It has long been suspected that paracetamol might raise the blood pressure, as do non-steroidal antiinflammatories, but this has not been definitively proved. Raising the blood pressure would be a bad thing, because it would probably lead to an increase in the number of heart attacks or strokes.

An Edinburgh experiment established that, in people already slightly hypertensive, paracetamol taken regularly for two weeks raised the blood pressure by 5 millimetres of mercury.

Doctors in England and Wales issue about 1,500,000 prescriptions for paracetamol annually, but it is a cheap over-the-counter analgesic available everywhere. There must be large numbers of people taking it all or most of the time.

The experimenters measured the subjects’ blood pressure at the start of the experiment and the end. So the question of when, exactly, the rise in blood pressure occurred – immediately, after two days, or after a week? – was not answered. Nor was the question of whether longer periods of consumption raise the blood pressure further.

Of course, the blood pressure in this experiment is what is called a proxy measure: it measures something that is strongly associated with something else that is of more direct clinical interest, namely heart attacks and strokes.

Though it stands to epidemiological reason that a rise in blood pressure would lead to an increased number of these events, this may not actually be the case, as many readers will have discovered.

As with all medication, there is the question of risk against benefit. Risk can be expressed both relatively and absolutely: a doubling of a trivial risk might be greatly outweighed by a small increase of a substantial risk.

Furthermore, the risk and benefit may be incommensurable: how much pain relief is equal to one extra stroke? (I won’t go into the evidence that the value of paracetamol in the relief of chronic pain is now a matter of dispute.)

Benefits and risks, moreover, have to be evaluated in the light of the alternatives, if any. Drug A may be risky, but drug B, the alternative, may be riskier. There is always the question of whether any risk at all has to be taken.

To this, likewise, there is seldom a definitive answer.

The conclusion of the report of the experiment is wonderfully indefinite (it is not only politicians who are slippery and evasive): ‘[It] adds to concerns regarding the safety of regular [paracetamol] treatment, especially at risk of developing ischemic heart disease and stroke.’

It adds to the concerns, but does not state how serious these should be. The sample was small. The experimental subjects were highly selected and not representative of the population as a whole. The start, duration and evolution of the hypertensive effect were unknown. A proxy measure was used. There are enough unanswered questions to keep clinical pharmacologists researching for decades.

In the meantime, the doctor is confronted by a specific patient who either should or should not take paracetamol. The doctor must exude a confidence that he or she may not feel, at least after reading the latest research.

Such is life.

Literary Lunch

In association with

Andrew Roberts

on George III: The Life and Reign of Britain’s Most Misunderstood Monarch A defence of not-so-mad King George

Norman Scott

on his memoir An Accidental Icon: How I dodged a bullet… The real story of the Jeremy Thorpe scandal

Julia Boyd

on A Village in the Third Reich The gripping tale of everyday Bavarian village life under Hitler

Tuesday 7th June 2022

At the National Liberal Club, 1 Whitehall Place, London SW1A 2HE

TO BOOK TICKETS email reservations@theoldie.co.uk or call Katherine on 01225 427311 (Mon-Fri 9.30am-3pm). The price is £79 for a three-course lunch including wine or soft drinks l Fish and vegetarian options available on advance request l Meet the speakers from 12 noon; lunch at 1pm l Authors speak 2.30