Scientists are warning about the risks posed by paracetamol after it emerged the painkiller had become the leading cause of liver failure in the US.
Researchers say pack sizes should be reduced further
The annual proportion of cases caused by paracetamol - known in the US as acetaminophen - had risen from 28% in 1998 to 51% in 2003, researchers said.
The US team found just 20 pills a day - the recommended maximum is eight - was enough to kill, New Scientist reported.
Experts said restrictions on sales had helped cut the number of UK cases.
Since 1998 in the UK, pharmacies have been advised not to sell more than one pack of 32 paracetamol tablets to any individual.
Other retailers are limited to 16, down from 24.
The US Acute Liver Failure Study Group, involving researchers from a host of US universities, analysed data on 662 patients treated for acute liver failure between 1998 and 2003.
Among the 275 painkiller-related cases, 48% were unintentional, 44% were attempted suicide, with the rest being unknown. Over a quarter of the cases resulted in death.
Those who had not meant to overdose tended to be taking several products containing the drug.
The investigators found as little as 10g - the equivalent of 20 pills - could cause liver failure.
Dr Anne Larson, co-author of the report, which first appeared in the Hepatology journal, said there needed to be more education for patients, doctors and pharmacies about the risk the painkiller posed.
And she also called for tighter restrictions in the US.
"Efforts to limit over-the-counter packaging size and to restrict prescription of acetaminophen may be necessary to reduce the incidence of this increasingly recognised but preventable cause of liver failure."
John O'Grady, of the Institute of Liver Studies, at London's King's College Hospital, said since the restrictions had been in place in the UK, there had been a 30% reduction in hospital admissions for liver failure related to the drug.
He added the warnings should be considered in the context of the number of people using the painkiller - over 500m tablets are sold each year in the UK.
He said: "Educational initiatives to highlight the range of preparations containing paracetamol, together with advice on maximum daily dosing, have potential benefits, especially with respect to unintentional overdosing."