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Six adults a week who have poisoned themselves with New Zealand's most widely used painkiller are seen, on average, at Auckland City Hospital.
A specialist in the adults' emergency department, Dr Bernard Foley, said a few of the patients accidentally took too many doses of paracetamol for a headache, but in most cases people had deliberately harmed themselves.
An Auckland mother is calling for greater restrictions on supermarket sales of medicines after her daughter's overdoses.
She said her teenage daughter had twice overdosed on painkillers.
On the first occasion, she obtained them from the home medicine cupboard; on the second, she took paracetamol she had bought at a supermarket.
"Before then, she was the nerdiest, straightest kid - teacher's pet, never did anything wrong."
"My husband and I were splitting up. She was at [secondary school] and struggling to fit in. Quite a few of the girls were cutting themselves and she was doing that."
The teen was treated both times at Starship children's hospital and recovered. She received counselling and was now at university and doing well.
Her mother had a lock put on her medicine cupboard after the first overdose.
She now wants supermarket sales of all drugs banned, or at least new tobacco-like requirements that stocks be put behind the counter and that sales be only to adults who can prove their age.
The risks of the drugs justified this, she said.
Consuming large amounts of paracetamol at one time can cause life-threatening liver failure.
Dr Foley said one or two paracetamol overdose patients a week at his hospital were in a serious enough condition for intravenous therapy with the antidote glutathione, which was very successful if started soon enough.
On average, one patient every two years was referred for consideration of a liver transplant due to failure to respond to the therapy.
In the past 10 years, one had received a transplant and four were considered unsuitable because of medical reasons.
Paracetamol was a useful drug and safe if used according to the label, Dr Foley said.
The benefits to the community of having small packs available at supermarkets outweighed the risks.
In the United States, the Food and Drug Administration is yet to review advisory panel recommendations to reduce the single maximum dose of paracetamol - known there as acetaminophen - from 1000mg to 650mg.
The panels also recommended reducing the maximum daily dose, but did not specify by how much.
New Zealand's Ministry of Health indicated changes to the rules for supermarket sales were unlikely.
Pharmacy adviser Chris James, of the ministry's Medsafe unit, said it was monitoring US developments, including concerns about the drug's availability over the counter.
He said that unlike the US, where packs of 1000 tablets could be sold, packets in New Zealand supermarkets contained a maximum of 10g of the drug - typically in 20 500mg tablets.
Larger packs were available over the counter only from pharmacies.
The largest pack size routinely sold in New Zealand pharmacies contained 100 500mg tablets.
People needing help can call Lifeline, 0800-543354.