MILLIONS of people are putting themselves at risk of suffering a toxic overdose from Britain’s most common painkiller.

Research has found that misusing paracetamol is a major health risk, leading to unintentional overdoses and even acute liver failure.

Experts warn that people in pain often ignore the recommended dosage of the popular over-the-counter pill.

Some, particularly the elderly, often forget how many they have taken. And others inadvertently take too much when they use other products containing the drug, such as cold and flu remedies.

Previous research has shown damage from a build-up of the drug in the system can be fatal.

People are warned not to take more than two 500mg pills in any four-hour period and no more than eight doses, to total 4g, over a 24-hour period.

Scientists in America say a “significant” number of adults are at risk of unintentionally overdosing and the problem requires “urgent attention”.

Dr Michael Wolf, from Northwestern University in Chicago, looked at the prevalence and potential misuse of pain medication containing acetaminophen, the main chemical ingredient in paracetamol.

The researchers warn the ease of access to such drugs is a major challenge to patient safety as many lack the health literacy skills to self-administer them appropriately.

Paracetamol

In fact, they say some people “self-prescribe”, making their decision about which over-the-counter medicine they need to treat their self-diagnosed symptom or condition.

For the study, which appears online in the Journal of General Internal Medicine, Dr Wolf and colleagues interviewed 500 adults receiving outpatient care at clinics in Atlanta and Chicago between September 2009 and March 2011.

More than half reported some acetaminophen use and 19 per cent were “heavy users”, meaning they took it every day or at least a couple of times a week in the previous six months.

Researchers tested whether these patients could work out the correct dose of a single medication and what their risk was of so-called “double- dipping”, by which they took two products containing paracetamol at the same time, therefore exceeding the recommended dose. Results showed nearly a quarter were at risk of overdosing using a single paracetamol product, by exceeding the 4g limit within 24 hours. Five per cent made serious errors by overdosing at more than 6g. In addition, nearly half were at risk of overdosing by “double-dipping”.

The authors concluded: “Many consumers don’t recognise or differentiate the active ingredient in over-the-counter pain medicines, nor do they necessarily closely adhere to package or label instructions.

“Misunderstanding of the active ingredient and proper instructions for medications containing acetaminophen is common. Potential for errors and adverse events associated with unintentional misuse of these products is substantial.

“Given the prevalence of the problem, risk of significant adverse effects, and lack of a physician to guide decision making, we believe this to be a serious public health threat requiring urgent attention.”