TORONTO - A new study shows prescriptions for high-dose formulations of opioids like oxycodone and morphine jumped by 23 per cent in Canada between 2006 and 2011, despite guidelines advising doctors against giving most patients such elevated doses.
Researchers at St. Michael's Hospital in Toronto and the Institute for Clinical Evaluative Sciences found the rates of high-dose opioid dispensing across Canada increased from 781 units per 1,000 people in 2006 to 961 units in 2011.
Put another way, that's almost one high-dose opioid pill or patch for every person across Canada.
Dispensing rates remained relatively stable over the six-year period in Alberta and British Columbia, while rates in Newfoundland and Labrador and Saskatchewan rose dramatically.
Ontario had the highest dispensing rate at 1,382 units per 1,000 people, while Quebec had the lowest rate at 368 units per 1,000 people.
Provinces also differed in which opioids were most often prescribed. In Alberta and Ontario, oxycodone was the top choice, while B.C. doctors most often prescribed morphine.
"We found that high-dose prescribing was widespread across the country, but the prevalence differed considerably between provinces," said lead author Tara Gomes. "These findings suggest that although a national strategy is likely necessary, different provinces may need slightly different approaches."
More than 180 million units of high-dose opioid tablets and patches were dispensed across Canada during the study period. Almost half of them were oxycodone, followed by morphine tablets, hydromorphone tablets and fentanyl patches.
Canada and the United States have the highest levels of prescription opioid use in the world. On average, more than 30 million high-dose tablets or patches of the highly addictive drugs are dispensed in Canada each year.
"These results have important public health and policy consequences, given the elevated risk of overdose among individuals treated with high doses of these drugs," says Gomes.
Until recently, clinical practice guidelines provided no recommended maximum dose and many experts suggested that the dose could be increased with little risk of harm.
However, opioid doses equivalent to 200 milligrams of morphine per day now are considered "watchful doses," according to Canadian clinical practice guidelines. The guidelines, introduced in 2009, recommend clinicians carefully consider the potential risks of addiction and overdose before prescribing a dose that exceeds this threshold.
The per capita rate of high-dose opioid dispensing increased steadily in Canada between 2006 and 2008 before plateauing in 2009 and 2010, coinciding with the release of Canadian guidelines and a study showing that the rate of fatal opioid overdoses had increased dramatically in Canada.
The study was published Friday in the journal Canadian Family Physician.
