A lack of evidence that the main drug used to treat death cap mushroom poisoning is effective has highlighted the dangers of eating wild mushrooms found in and around the national capital.
Two people died and another became critically ill after eating the deadly fungi at a New Year's Eve dinner in 2011.
The case triggered a review of 12 cases of suspected death cap poisoning reported in the ACT and NSW between 1999 and 2012.
Eight of the 12 patients sustained serious liver damage and four died, according to the study published in The Medical Journal of Australia.
Study co-author and Canberra Hospital emergency medicine director Michael Hall said supplies of a possible antidote, Silibinin, were kept in the ACT, NSW and South Australia.
But it was unclear how effective Silibinin actually was.
"It's essentially illegal in Australia - you have to use the special import scheme to import it, and as our paper shows, there's not good evidence it works anyway,'' he said.
During one cluster of cases, hospitals had to scramble to source sufficient supplies of Silibinin, which is derived from the milk thistle, Silybum Marianum, and used in European hospitals.
The rarity of death cap poisoning made it difficult for large-scale scientific studies to be conducted on the efficacy of Silibinin.
"There's very much a lack of evidence on how to best treat them. You can't realistically expect people to run large controlled trials for something that's relatively rare,'' Dr Hall said.
People who consume death cap mushrooms can initially suffer from gastroenteritis-type symptoms and eventually kidney injury, liver failure and multi-organ failure.
Eight of the patients studied were not long-term residents of the ACT and six were immigrants from Asia.
"Eating wild mushrooms is a dangerous thing in Canberra and the fact is when you read through these cases the majority of Canberra people are probably aware of that,'' Dr Hall said.
"We teach junior doctors in Canberra that if you see a patient with an unexplained gastro-type illness, you have to ask about wild mushrooms. Now, you wouldn't teach that in any other city in Australia.''
Death cap mushrooms often grow near established oak trees and are found when there is warm, wet weather. In Canberra this usually occurs in late summer or early autumn. The poisonings that occurred at the end of 2011 were after unseasonal summer rains.
Harmonie club chef Liu Jun and kitchen hand Tsou Hsian died after eating wild mushrooms Mr Liu had cooked in a stir-fry.
A third man became critically ill while a fourth had only minor symptoms.
In response to the two deaths, a public education campaign was developed that targeted people from non-English-speaking backgrounds and visitors to the ACT.
A Health Directorate spokeswoman said a campaign would run at the start of this year's mushroom season.
The small button death cap, or white cap, mushroom can be very difficult to distinguish from an edible mushroom.
In Australia, death cap mushrooms are most commonly found in the ACT. But they are also seen in other parts of the south-east and some poisonings have been reported in Victoria.