TORONTO - Researchers are raising new concerns about opioids, in particular some of the high doses of strong painkillers being prescribed to socially disadvantaged people in Ontario.

A study by the Institute for Clinical Evaluative Sciences finds that Canadian guidelines for opioid therapy are not always being followed. And preliminary data indicate that patients who receive high opioid doses have a much greater likelihood of dying than a member of the general population.

"While prescribing has been increasing of opioids, as expected, the daily dose that people are receiving is also increasing over time, and that increase is most pronounced among people who are being prescribed long-acting oxycodone -- so this is drugs like OxyContin," said Tara Gomes, a researcher and epidemiologist at the institute.

"About a third of people who are receiving prescriptions for long-acting oxycodone are in fact receiving doses that are considered to be high or very high dose, based on published clinical guidelines."

The term opioid covers powerful painkillers like morphine, codeine and oxycodone.

Researchers looked at prescriptions for patients aged 15 to 64 under Ontario's public drug plan over a six-year period from 2003 to 2008, and found opioid prescribing rates rose 16.2 per cent. By 2008, 180,974 people were receiving nearly 1.5 million opioid prescriptions annually. The findings are published Tuesday in the journal Open Medicine.

Patients with cancer and in palliative care who were taking opioids were not included in the study.

Gomes said several guidelines define an upper dose, or watchful dose, at about 200 milligrams per day. In 2008, 32.6 per cent of people treated with OxyContin received daily doses equivalent to more than 200 mg of oral morphine per day.

"People who were receiving high or very high doses of opioids were 10 times more likely to die within two years (compared to) the general population," she said in an interview.

Among patients who had prescriptions filled for high or very high doses of opioids in 2004, almost 20 per cent of the deaths during the subsequent two-year period were related to opioids.

The Office of the Chief Coroner for Ontario classified 302 deaths as opioid-related, including 45 confirmed as suicides, the study showed.

Gomes described the findings as troubling. The median age of people who were dying of opioid-related causes was 46 years.

"So these are young people that are either being treated with opioids for pain, or have begun to abuse these drugs and become addicted to them, and are dying as a result of that," she said.

Multi-doctoring, in which addicts visit more than one doctor for a painkiller prescription, is considered to be part of the problem, experts say.

Gomes said more education is needed for the public about the risks associated with these drugs, and for physicians and pharmacists about the dangers of prescribing high doses.

Having real-time access to electronic records that show the prescribing history of patients could help address problems of drug dependency and addiction, she said.

Dr. Philip Berger, chief of the family medicine department at St. Michael's Hospital in Toronto, said the study is an extension of earlier findings, looking more closely at deaths and prescribing rates in a socially disadvantaged group.

He said the Ontario Ministry of Health, the regulatory body -- the College of Physicians and Surgeons of Ontario -- and the University of Toronto have "utterly failed until very recently to confront an epidemic of opioid deaths which has been known for a long time."

But he said the ministry has finally responded with its plan for real-time monitoring that would allow a pharmacist to ascertain whether a patient received a similar prescription on the same day or recently, inappropriately and from more than one doctor.

"That's good," he said, "but the system's not implemented yet."

And he noted that regulatory bodies have issued new guidelines.

"I'm not sure how much that is penetrating the consciousness of Canadian doctors. I hope so. But we're not going to know until there's more studies done."