VANCOUVER -- Desperate for relief from unbearable pain following knee surgery, Lorna Bird says she was forced to buy drugs from the Downtown Eastside streets of Vancouver when her doctor stopped prescribing an opioid in response to new standards aimed at preventing fatal overdoses.

"I started with heroin because I couldn't stand the pain," Bird said, recalling her fears about dying from fentanyl-laced street drugs because "everybody was croaking" and she didn't want her grandchildren dealing with that outcome.

Bird, 60, said the prescription opioid hydromorphone, which is five times more potent than morphine, numbed the pain after her surgery in December 2014 but her doctor tapered off the dosage before stopping it despite her continuing pain.

Experts say Bird is among thousands of Canadians facing the predicament of getting pain-numbing street drugs after being weaned or taken off opioids to which they've become addicted.

Bird said concerns about contaminated heroin had her spending $100 a day on cocaine instead but she tries not to use it alone because she worries about overdosing if the powerful painkiller fentanyl has been added to anything she buys on a street corner.

Bird recalled a conversation with her doctor: "I told him, 'I'm shooting up powder now, cocaine, because that's what kills the pain.' "

She said he cited standards by the College of Physicians and Surgeons of British Columbia for his decision before resuming a much lower dose of hydromorphone, along with methadose.

Bird said she continues taking both drugs but they're not enough to deal with her pain so she also injects cocaine.

"Sometimes it's hard just to get to the place where you buy your stuff," she said through tears. "You can hardly wait to get that needle, just to get that sense of relief. It's awful to have somebody hold you and have to walk you there. And then you're doubled up in pain."

Benedikt Fischer, a senior scientist at the Toronto-based Centre for Addiction and Mental Health, said between 500,000 and one million Canadians are addicted to opioids because doctors have overprescribed the narcotics for years.

Updated prescribing guidelines released last month by the National Pain Centre at McMaster University in Hamilton call on physicians to limit dosages of drugs such as hydromorphone, oxycodone and the fentanyl patch to the equivalent of 90 milligrams of morphine per day.

The centre also recommended physicians taper off medications or even discontinue the drugs that could lead to dependence with long-term use.

"The new guidelines are basically an attempt to turn around a huge freighter ship that's moving in one direction, and now we're doing a 180-degree turn," Fischer said, adding a "catastrophic" number of deaths could result if more patients resort to taking street drugs.

The Public Health Agency of Canada has said nearly 2,500 people died from opioid overdoses in 2016 alone. Fischer said in the last decade, up to 20,000 Canadians have fatally overdosed on the potent narcotics.

He said while new guidelines were needed to prevent an epidemic of overprescribing, they were not matched with systemic changes, such as non-pharmaceutical pain-management strategies.

"All of a sudden they're dropping all these patients or cutting them off their opioids," he said of doctors who prescribed excessive amounts of narcotics for chronic, non-cancer pain.

"I see more people dying," he said, noting Canada is already the second-largest consumer of opioids, second only to the United States.

"What really most urgently needs to happen in our system, Canada-wide, is system management," said Fischer, adding services remain fragmented even in British Columbia, where a public health emergency has been declared over the fatal-overdose crisis that claimed over 1,400 lives between January 2016 and March 2017.

The spike in overdose deaths prompted the College of Physicians and Surgeons of British Columbia to replace its opioid-prescribing guidelines last year with mandatory professional standards that allow for complaint hearings and disciplinary actions, such as fines and licence suspensions against non-compliant physicians.

Evan Wood, director of the BC Centre on Substance Use, said the opioid crisis demands a two-pronged approach -- one to deal with patients who've become dependent on the narcotics and another for people who have never been prescribed the narcotics but need pain management.

Addicted patients must be continued on lower, stable doses of the treatment while being monitored to prevent access to street drugs, Wood said, and people with new pain issues should not be prescribed the narcotics except in rare cases and only for a few days and on a low dosage.

"Once somebody's opioid-addicted, simply cutting them off of opioids can lead to all sorts of problems with people turning to the street and transitioning to intravenous use and, of course, with fentanyl out there in the drug supply it can be very, very, very dangerous."

Fischer and Wood agree that thousands are turning to street drugs as a result.

Overall, a pain management strategy must be a key part of the health-care system, Wood said.

"There needs to be an investment in interdisciplinary pain clinics in order to provide pain treatment," he said. "We got into this crisis with the overprescribing of opioids, OxyContin and the like, but we need to be much more nuanced about how we address that crisis now."