Doctors may not appreciate how potent OxyContin is, medical toxicologist Dr. David Juurlink says. (Toby Talbot/Associated Press)

Drugs like OxyContin are killing users in Ontario at twice the rate they were in 1991, a new study suggests.

The rate of deaths involving narcotic painkillers went from 13.7 per million in 1991 to 27.2 per million in 2004, said Dr. David Juurlink, a medical toxicologist at Sunnybrook Health Sciences Centre in Toronto.

He and his colleagues published their findings in Monday's issue of the Canadian Medical Association Journal.

In particular, deaths from oxycodone, mainly marketed as OxyContin, increased about fivefold after the drug was added to Ontario's formulary, the list of drugs covered by the province's health plan.

The cause of death was deemed unintentional by the coroner in 54.2 per cent of the cases and undetermined in 21.9 per cent.

The researchers looked at prescribing data from IMS Health Canada, which collects information from about two-thirds of Canadian pharmacies, reviewed records from Ontario's chief coroner, and tracked patients' medical visits based on health-care databases.

"The frequency of visits to a physician and prescriptions for opioids in the month before death suggests a missed opportunity for prevention," the study's authors concluded.

Between 1991 and 2004, 7,099 deaths with complete records were attributed to drugs or alcohol. In 3,406 of these deaths, or 61.9 per cent, opioids were implicated as a cause of death.

"I think what needs to happen is that patients, and probably to a greater extent their doctors, need to develop an appreciation for the toxicity of this drug and probably a respectful fear of using this drug in patients who are prone to misuse or who are prone to consume alcohol or sleeping pills. It's just a bad combination," said Juurlink. "It's a setup for disaster."

On a milligram-for-milligram basis, OxyContin is 50 per cent to 100 per cent more potent than morphine, Juurlink noted.

"I think that many physicians really don't appreciate how potent this drug is," he said. That lack of appreciation can lead to complacency on the part of doctors prescribing it.

The rise in opioid-related deaths was due in large part to "inadvertent toxicity," or accidental, the study's authors said.

The societal burden of death and disease related to opioids in Canada is "substantial" they said. The annual incidence of opioid-related deaths in 2004, 27.2 per million, was between that of HIV infections at 12 per million and sepsis or blood poisoning at 40 per million.

In a commentary that accompanies the study, Dr. Benedikt Fischer of Simon Fraser University in Burnaby, B.C., and his co-authors noted that as prescription drugs are involved in more overdose deaths than either heroin or cocaine in North America, the profile of those dying may be shifting from marginalized people to more "middle class."

"I didn't choose this," said Phyllis, a woman in London, Ont., who is recovering from an addiction to OxyContin. CBC News is protecting her identity.

"It took me over. I didn't choose this. I didn't want to be addicted. I grew up in a fantastic home with great parents and grandparents."

Phyllis said she experimented with OxyContin to help her deal with problems she was having in her life.

"Well, it didn't really. It made me forget," she said.

Fischer said Ontario is on the higher end for consumption but that the overall picture is likely similar in other provinces.