Experts say heroin and other opioid users are at risk of being duped into thinking it's a pure version of their drug of choice.

Carfentanil is a highly potent opioid that is so strong a person can receive a fatal overdose simply by touching it. A dose that is smaller than a grain of salt can also kill.

The drug has been linked to the 2002 Russian gassing of Chechen rebels who had taken hostages in a crowded theatre.

The AFP recently seized the drug and presented it to health authorities, with tests revealing it to be the highly dangerous drug.

Chief health officer Paul Kelly said he wasn't surprised to find the drug - having been on the look out for it for the past two years - but very worried about its impact.

"This is a veterinary drug and it should be left to the elephants and rhinos and so on," he said.

"The potency is enormous.

"Carfentanil is one of the most potent Fentanyl analogues with a potency estimated to be 10,000 times that of morphine.

"The drug is so potent that a safe dose is so small it cannot be measured outside a scientific laboratory as domestic scales do not provide sufficient accuracy."

Emergency department doctor David Caldicott, who has been pushing for a drug testing trial in the ACT, said it was another example of how testing of drugs at the point of consumption could save lives.

He warned while the best way to avoid harm was to avoid drugs, opioid addicts faced the most risk.

"One of the best ways to sham consumers is to add a product of very high potency to what perhaps is very heavily cut," he said.

"[Dealers] push on the public a version that's very pure when in fact it has been adulterated."

Dr Caldicott warned the strength and risk of overdosing on Carfentanil could not be overstated.

"You might think of you're aficionado of The Bourne Identity and believe it's very easy to sedate an entire theatre with a mystery gas [but] it's incredibly difficult to do something like that," he said.

Dr Caldicott said immediate medical attention and the administration of antidote was key to treating affected users.

He urged anyone who believed a friend, family member or stranger was overdosing to call an ambulance.

"It won't be the overdosing person trying to seek treatment, they will be busy trying to die," Dr Caldicott said.

"It's a terribly nerdy approach but if you don't want to get hurt by drugs, don't do them."

Dr Caldicott heralded the ACT's approach to drug harm minimisation, saying similar drug warnings were rare in other jurisdictions.

"We are a small jurisdiction, we know each other, it is very easy for us to collaborate closely," he said.

"This has been a detection from a law enforcement perspective and it is on the basis of law enforcement and health recommendations together that this information has been released.

"In other jurisdictions this has not been the case."