The annual rate of opioid-related deaths jumped by 242 per cent between 1991 and 2010, said lead author Tara Gomes, a scientist at the Institute for Clinical Evaluative Sciences, or ICES, which conducted the study published Monday in the journal Addiction.
"In 2010, we found that there were approximately 550 deaths related to opioid overdose, which equates to one or two deaths every day," said Gomes, noting that the annual fatal overdose rate two decades earlier was 127.
The highest proportion of deaths was clustered among young adults, say the researchers, who analyzed provincial coroner's records from 1991 to 2010.
"One in every eight deaths in people aged 25 to 34 were related to opioid overdoses," said Gomes. Twenty years ago, the rate for that age group was one in 25.
"Given the concentration of deaths in the younger ages, we found that opioid-related deaths had a considerable societal burden" she said. "In 2010, these deaths led to over 20,000 years of life lost,"
In all, 5,935 Ontarians died from opioid overdoses in the 20-year period.
"These could be people who purchased the drugs on the street, these could be people who received legitimate prescriptions and mistakenly took too much of the drug or escalated their dose without checking with their primary-care provider," Gomes speculated.
"These could also be people who have heard about recreational use of these drugs and knew to go into their parents' or grandparents' medicine cabinet and find the drug and try it. And never having taken the drug before, they can overdose after just one or two pills of a high-strength formulation."
Over the last two decades, several new products have come on the market, among them oxycodone. Doctors began prescribing the drugs more often to treat those with intractable pain, and often in increasingly potent doses.
"And I think the combination of these factors is likely driving a lot of this increased risk of opioid overdose that we're seeing, because there's a lot more of the products available, and as well these drugs are being used at higher doses," she said.
"And we have seen in past research that higher doses of opioids are associated with increased risk of overdose death."
Codeine, hydromorphone, morphine, fentanyl and oxycodone are the "big players" among the opioids, she said.
Opioid prescription rates have continued to rise, driven by aggressive marketing by manufacturers of the products to physicians, who she believes have become more comfortable with recommending them for patients suffering with hard-to-treat pain.
But drug-seeking behaviour by those looking to abuse the medications is also likely driving up prescribing rates, she said, adding that opioids' addictive nature can lead to someone visiting several doctors to obtain multiple prescriptions, a phenomenon known as double-doctoring.
Gomes suspects the escalation in opioid overdose deaths is likely occurring across the country.
However, there is no national database to track overdose deaths, said Benedikt Fischer, a professor of health sciences at Simon Fraser University in Burnaby, B.C., although the numbers are moving upwards in that province as well.
"It's an extremely worrisome picture that the number of deaths are going up and have been going up for many years the way they are," Fischer, who was not involved in the study, said of the Ontario findings. "And this is a huge death toll.
"We know that the number of opioid deaths is almost perfectly correlated to the amount of prescription opioids dispensed to the population. So, in essence, the number of deaths are a function of the amount of opioids prescribed and dispensed into the population."
In order to reduce the death toll from prescription opioids, a strategy needs to be found to reduce the amounts being dispensed, he said, noting that Canadians are the second-largest per capita users of these drugs in the world after Americans.
Fischer said that while chopping the overdose death toll has to begin with doctors cutting back on prescriptions, it's also critical to recognize that these medications play a key role in treating many patients with pain, including those with cancer.
"Let me be clear. We cannot afford to eliminate these medications. We need them," he said. "They're important to a lot of people with chronic and severe pain who need these drugs.
"But current prescribing and dispensing goes far beyond those parameters. It exceeds those hazardously."
The Ontario researchers have developed an interactive map of Ontario counties with the highest rates of opioid overdose deaths, including Thunder Bay and Sudbury, and large urban centres like Toronto.
Gomes said health-care providers need to ensure that patients understand the risks opioids may pose and that they should be "very careful" with their use.
"They shouldn't share their drugs, they shouldn't escalate their dose without consulting their physician and they should just be very aware that these are risky drugs that can be effective but can also be very dangerous."
Interactive map: http://www.odprn.ca/pyll/
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