Canadian national prescribing guidelines currently recommend
physicians try to avoid prescribing doses higher than 200 mg morphine or
the equivalent in the treatment of chronic non-cancer pain.
The rate of opioid use in Canada has fallen 13.7% since the publication in May 2010 of national guidelines for their use in chronic non-cancer pain, a new study has found. Yet rates of opioid-related hospital visits rose 13% between then and the end of 2013 the study found, possibly because people who continue to take some of these potent drugs are often being prescribed high doses, placing them at greater risk of overdosing.
The study, led by Tara Gomes, a scientist at the Li Ka Shing Knowledge Institute of St. Michael's Hospital and the Institute for Clinical Evaluative Sciences, and a principal investigator of the Ontario Drug Policy Research Network, was published in the open-access journal PLOS ONE.
The study found that rates of opioid use remained steady from 2003 until the publication of Canadian guidelines for the use of opioids for chronic non-cancer pain. After this time, the rate fell from approximately 27% of ODB eligible persons in the first half of 2010 to 23% in the second half of 2014.
However, the rate of opioid use was not further affected by the province of Ontario's enactment of the Narcotics and Safety Awareness Act in November 2011, the study found. A key component of that legislation was the requirement for prescriptions for narcotics and all other controlled substances to be disclosed to the Ministry of Health and Long-Term Care for monitoring and surveillance.
Both the national guidelines and the provincial legislation were designed to promote more judicious and appropriate opioid prescribing, which was expected to reduce the risk of overdoses, as has been seen in some jurisdictions in the United States.
"The decline in the rate of opioid use after the publication of national guidelines could reflect more comprehensive assessment of patient pain, medical mental health and substance use history by physicians before initiating opioid therapy," Gomes said. "However, it is also extremely important to ensure that clinicians are safely tapering opioid therapy in their patients and ensuring that patients have access to addiction services when necessary."
Gomes said that despite decreasing rates of opioid prescribing, among the remaining opioid prescription users, the proportion of high dose use more than doubled from 4.2% in 2003 to 8.7% in 2014.
In the last six months of 2014, 12,713 people in Ontario eligible for public drug benefits were treated with doses above 200 mg morphine (or the equivalent). Further, the study found 40.9% of recipients of long-acting opioids exceeded daily doses of 200 mg of morphine (or the equivalent) and 18.7% were treated with very high doses exceeding 400 mg morphine (or the equivalent).
Of note, in the last six months of 2014, more than half (55.4%) of long-acting oxycodone users, and more than three-quarters (76.1%) of fentanyl users were treated with daily doses exceeding the Canadian guideline's upper dose threshold of 200 mg morphine or the equivalent.
The study also found that rates of opioid-related hospital visits increased 34.5% from the first half of 2003 to the second half of 2004, but remained relatively stable between 2005 and 2009. Between 2010 and 2013, rates increased again, rising 13% from 12.4 to 14 hospital visits per 10,000 ODB-eligible persons. The rate of opioid-related hospital visits was not significantly impacted by the Canadian clinical practice guidelines in May 2010 or the Ontario legislation in November 2011. In 2013, there were 1,621 opioid related hospital visits among public drug beneficiaries in Ontario.
"The persistent growth in opioid-related hospital visits in recent years in Ontario could be explained by increased illicit opioid use if people previously using prescription opioids were denied access to these drugs without adequate dose tapering or addiction services," Gomes said. "Another potential explanation may be dosing errors among people switched from long-acting oxycodone to alternative opioids when formulary restrictions for OxyNeo were introduced in February 2012."
Gomes noted that one limitation of this study was that the majority of people eligible for the Ontario Public Drug Program are socioeconomically disadvantaged, so the findings may not be generalizable to the overall population. Despite this limitation, she suggested that these findings provide valuable information for physicians and policy-makers as they work toward improving opioid drug policy and appropriate prescribing practices in Ontario.