The dangerous white powder behind a mass overdose in Perth this week was destined to be mixed into illicit drugs and unwittingly consumed by hundreds of Australians, the Australian Medical Association has warned.

"We've known from 40-plus years of experience that criminal gangs that push poisons onto vulnerable people in our society like heroin, like cocaine, will routinely lace the product with other white powders." AMA President Michael Gannon said.

Nine young backpackers were rushed to hospital on Wednesday night after snorting what they thought was cocaine, only to minutes later slip into what was described as a "zombie-like state" where they became semi-paralysed and some began having seizures.

A resident outside the drug overdose house in Victoria Park ( ABC News: James Carmody )

By the time they arrived at hospital doctors said they were in a state of agitated delirium, hallucinating, with racing heart rates and several were placed in induced comas for their own protection.

Chemical tests revealed the powder, which they claimed had arrived in the post from New York addressed to an unknown person, was hyoscine, a substance found in tiny doses in some anti-nausea medications.

Dr Gannon said mixing other white powders into drugs to bulk them out was a cheap way for dealers to make more money.

"Sometimes it's as simple as that — they find a white powder that's not obviously detectable like sugar or salt, to increase the amount of money they will take from vulnerable people," he said.

"So any white substance has an appeal to the criminal gangs selling drugs in our community."

He said dangerous pharmaceuticals were frequently used because they could have sedative or psychedelic effects similar to genuine narcotics.

Security and regulation of such medications in Australia was incredibly strict because of their street value, but criminals continued to find access to these substances.

Dr Gannon said in the hands of untrained people, medical drugs that might have legal purposes could be just as toxic as household chemicals sometimes used by dealers to make their product go further.

AMA national president Michael Gannon said the backpackers were facing huge medical bills. ( ABC News: James Carmody )

However people continued to take drugs containing substances they knew nothing about.

"It is a game of Russian roulette and we should not be surprised when someone is harmed or killed," he said.

"Sadly some people will make that decision and it will be the last decision they make in their life."

Drug festival danger

Dr Gannon said thousands of people attending sold-out festivals, concerts and other events around the country today would take drugs such as these and it was not unlikely they would contain substances like hyoscine.

He said the medical field had been paying close attention to the harm-minimisation potential of pill-testing in these settings.

"We have needle exchange programs for people who are going to use heroin whether we like it or not, condom use for people who are going to undertake unsafe sexual practices whether we like it or not," he said.

"So there is potentially scope there and within a well-designed, well-constructed trial, maybe we should have another look at it."

Festival-goers have been warned about taking drugs laced with unknown substances. ( AAP: Future Entertainment )

But he said such trials were fraught with ethical problems.

"Our concerns with pill testing are a lot more sophisticated than an argument that it encourages permissiveness when it comes to illicit drug use," he said.

"Certainly, pill testing is getting better, but the question is what then happens to the pill?

"Where this has been trialled in other parts of the world there's evidence that people will then on-sell the pill to someone else, and that is obviously a disaster for everyone."

Spotlight on healthcare cost

Of the nine backpackers who overdosed in the Perth suburb of Victoria Park on Wednesday, one French national remains critically ill in intensive care. The other eight have since been discharged from hospital.

Aside from any potential lasting medical effects of their overdoses, all but one of the group now face hefty medical bills with no cover under Australia's Medicare system and any travel insurance likely to be void by the nature of their incident.

Only one member of the group — an Italian — is from a country with a reciprocal medical agreement, where the country pays for the cost of medical care.

Eight of the patients have since been released from hospital. ( ABC News: James Carmody )

Dr Gannon said while the priority was ensuring the backpackers got the best medical care available, it was a concern that the WA Health Department could fail to recoup the cost of these bills.

"This is an impost on the Australian taxpayer so we would support measures that would maybe tighten up some of the immigration requirements or some of the health insurance requirements," he said.

"The most important thing is compassion if people fall ill and one very basic ethical principle for doctors is you provide the appropriate level of care, especially in an emergency.

"But it is a reality that every year millions of dollars of fees are actually left unpaid by ineligible patients."

Dr Gannon said the fact the backpackers were facing medical bills potential reaching thousands of dollars illustrated just how expensive medical care in Australia actually was.

He said Australians often did not realise how much taxpayer money goes towards funding the health care of themselves and others.

"One of the successes of Medicare and one of the problems of Medicare is that the true cost of healthcare is not visible to Australians," he said.