Deaths from paracetamol overdoses fell by 43% in England and Wales in the 11 years after the law on pack sizes was changed, according to a study.
But the number of people taking paracetamol overdoses had not declined, says the Oxford University study published in the BMJ.
In 1998, the government restricted pack sizes in the UK to 32 tablets in pharmacies and 16 in other shops.
Researchers say the figures should not lead to “complacency”.
Paracetamol overdoses are a common method of suicide and a frequent cause of liver damage.
Previous studies suggested the decision to restrict the size of packs of paracetamol sold over the counter showed initial benefits in both these areas, but there was no data on the long-term impact.
Using figures from the Office for National Statistics, the Oxford researchers looked at deaths involving paracetamol in people aged 10 years and over between 1993 and 2009.
They found there were fewer deaths after the legislation was introduced in 1998 than would have been predicted based on trends dating back to 1993.
The study also found that patients registered for a liver transplant because of a paracetamol overdose had reduced by 61% following the legislation. This was equivalent to 482 fewer registrations over 11 years.
Prof Keith Hawton, lead researcher from the University of Oxford Centre for Suicide Research, said lives had been saved since the change in the law.
“While some of this effect could have been due to improved hospital management of paracetamol overdoses, we believe that this has in large part been due to the introduction of the legislation.
“We are extremely pleased that this measure has had such benefits, but think that more needs to be done to reduce the toll of deaths from this cause.”
Despite the reduction in deaths from paracetamol, the study found there had been no decline in overdose cases after 1998.
The study added that additional measures would be needed to reduce the death toll, such as lowering the limit on tablets in packs further, reducing the paracetamol content of the tablets and enforcing the legislation more effectively.