It was one of the most frightening moments of her life.

A friend overdosed after taking the powerful painkiller fentanyl, started convulsing on the floor and stopped breathing.

Filled with fear, Jessica sprinted to her car outside and seized a pre-filled syringe kept for emergencies. She administered the unconscious woman with an overdose antidote and waited for the ambulance to arrive.

"You'll be surprised how quickly someone turns cold," the former drug dealer told Lateline.

"They turn purple, they're not breathing, and it's just like seeing a dead body on the floor."

Former drug dealer Jessica compares using high-strength opioid fentanyl to Russian roulette ( ABC News )

She sold heroin for a decade but refused to sell fentanyl after seeing 15 people overdose.

"It's a killer drug," she said.

"When I had no heroin, people would ask me if I had fentanyl or if I could get fentanyl.

"You can go buy $100 or $200 worth of fentanyl and be smashed. To get that equivalent of heroin, the heroin most people can get their hands on, you would need to spend $400, $500, $600."

The escalating number of drug overdose deaths in the United States last year has been linked to an influx of illicitly-manufactured fentanyl.

Accurate figures on the illicit use of fentanyl and related fatal overdoses in Australia are not readily available.

But health experts say the number of fatal overdoses from prescription painkillers is highest in rural town towns like Taree, just a few hours drive north of Sydney.

In the past 18 months, Australian Border Force has intercepted 30 fentanyl packages through the mail.

James Martin, a criminologist at Macquarie University, confirmed authorities are closely monitoring fentanyl trends.

"Prescription drugs here in Australia are the second most popular traded category of drug type," he said.

"We are seeing increasing levels of fentanyl being traded on the dark net."

'I never thought I'd wake up in jail'

In Taree, recovering addict Stephanie said the drug was "easy to get" from street dealers and even patients suffering from terminal cancer.

Fentanyl cost recovering drug addict Stephanie her house and daughter ( ABC News )

"I loved it. I would have a box all to myself," the 37-year-old said.

"It was like somebody pushing you down, or somebody putting a very heavy coat on you, instantly warm."

Stephanie has regrets. She now lives in a caravan park, has enrolled in a methadone program and is attempting to rebuild her relationship with her daughter.

"I never thought I'd do the things that I did to help support my habit... I never thought I'd wake up in jail," she said.

Cutting corners

The painkiller is a synthetic, factory-made opioid roughly 50 times more powerful than morphine.

Some addicts extract fentanyl from the slow-release patches prescribed to people suffering constant pain.

Current user John (not his real name) said a single 100ml patch could be "easily" be divided into a dozen pieces worth $50 each.

Every time he shoots up, it's a gamble.

Long-term drug addict 'John' says many friends have overdosed on fentanyl ( ABC News )

He says he knows 14 people who have overdosed, eight of them close friends.

"You don't know where in the patch the fentanyl is," he said.

"You could have that one patch that has 99 per cent of it in... and that's the end of you."

US authorities responded to the heroin epidemic by getting the opiate antidote naloxone into the hands of emergency workers.

NDARC researcher Amanda Roxburgh said similar measures were needed in Australia to prevent fatal overdoses.

"We know when people inject fentanyl it's a much shorter time to overdose than when people inject heroin," she said.

"I think we absolutely need to increase the availability and accessibility of naloxone."

Meanwhile, Jessica, at 25, has made the first steps on what she hopes may be the path to recovery.

"You lose a lot of yourself when you sell drugs because it's not about you any more. It's about the drug," Jessica said.

"When you have a dependence, you'll do anything to get the drug. Anything. You lose your morals, you lose your ethics, you lose everything."