The drug that caused a mass overdose among nine backpackers who were hospitalised in Perth has been identified as a common prescription drug called hyoscine.
Western Australia Police said hyoscine - also known as scopolamine, which is used in low doses as a sedative and for the treatment of travel sickness - was the only identifiable drug detected in the samples taken from the patients.
The drug has gained notoriety internationally from its use as a truth serum.
The seven men and two women aged between 21-25 took hyoscine and fell into an unconscious or semi-conscious state, WA Police said.
The nine foreign backpackers, including five from France, were rushed to hospital in various states of "agitated delirium".
The group of backpackers, aged 21 to 25, thought they were snorting cocaine on Tuesday night but suffered violent reactions, with three put in intensive care in induced comas.
Two people, both French, remained in a critical condition on Thursday while a German woman was still in an induced coma in a stable condition with the rest released from hospital after paramedics were called to a house in the Perth suburb of Victoria Park on Tuesday night.
Royal Perth Hospital emergency doctor David McCutcheon said the group would have died if they had not been treated by medical staff.
Dr McCutcheon said on Wednesday they were brought to hospital in a "state of agitated delirium".
"They were hallucinating, their hearts were racing, several of them had to be put in a medically induced coma for their own protection and I really need to emphasise how seriously unwell they were," he said.
- with AAP
