A former ER doctor whose career was derailed by an opioid addiction hopes he can still offer one last piece of medical advice: don't become a "slave" to fentanyl.

Darryl Gebien, 46, says he has nothing left to lose by publicly addressing his struggle with fentanyl addiction, which has had led to serious legal and professional consequences in his life. Gebien is currently awaiting sentencing for writing hundreds of bogus fentanyl prescriptions, and for one count of trafficking. His medical licence has also been placed on hold, as he awaits sentencing for his crimes later this month.

"Regardless of whether I have my medical licence right now, I still care about people," Gebien told CTV News Channel on Sunday. "To me, this is the most noble thing I can do."

"I've only got something to gain by sharing my story and hoping other people will get it, like people who are actually addicted," he said.

Fentanyl is a prescription opioid used to treat chronic pain, with a potency 50-100 times higher than morphine or heroin. Fentanyl abuse has been on the rise in recent months, both on its own and as a potentially deadly ingredient in designer drugs.

Some city fire crews have been outfitted with special kits containing naloxone, an antidote for fentanyl overdoses, in order to stem the rise in deaths caused by the drug.

Gebien says he became addicted to fentanyl in May of 2014, following Percocet abuse. He was originally prescribed Percocet to treat a back injury in 2008, but he admits he stayed on the painkiller to treat emotional pain while working in an emergency room in Barrie, Ont.

"It's a very slow spiral, that escalating use of the Percocet," he said.

Gebien says he first obtained fentanyl from his mother by "misleading" her about his pain, in order to get his hands on a set of patches. "I abused it and I took it in an improper way after I Googled it," he said.

The former ER doctor says the fentanyl was "incredibly powerful," and likely would have killed him if he had not already built up a resistance to painkillers from his years of using Percocet. "It just accelerated the addiction even more… until things completely fell apart for me," he said.

Gebien says he became addicted to the drug "after the first dose," and that he lost 40 pounds over the course of six months while using it. He recalls frequently lying to get his next fix, and struggling with feelings of self-loathing while operating in "slavery to the drug."

"This was in the depths of my addiction," he said.

Gebien was first charged in November of 2014, in connection with forged documents prescribing fentanyl.

He has since gone through treatment for his addiction, which he says involved 32 hours of "pure discomfort," six months of physical recovery and 18 months of struggling with anxiety.

"I'm at the peak of my life now," he said. "How can I get hurt any further?"

Gebien pleaded guilty last December to writing fake prescriptions for 445 fentanyl patches. The fake prescriptions were written between August 2013 and November 2014.

He is due back in court on Apr. 18 for sentencing.