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Opioid Agonist Therapy Underused, Data Suggest

Kate Johnson


Few patients with opioid toxicity receive opioid agonist therapy (OAT), data suggest. 

In a retrospective study that examined about 21,000 hospital visits related to opioid use disorder (OUD) in Ontario, Canada, 4.1% resulted in community-based initiation of OAT within 7 days of discharge.

photo of Tina Hu
Tina Hu, MD

"From what I have seen as a physician, I suspected that OAT initiation rates would be low. However, I did not think that it would be so low," study author Tina Hu, MD, family physician and assistant professor of family and community medicine at the University of Toronto, told Medscape Medical News. "OAT is a proven and effective treatment for OUD, reducing both morbidity and mortality. In the midst of a public health crisis…. [I]t is inconceivable to me that we are not using every healthcare encounter as an opportunity to discuss OAT with patients with OUD and initiate life-saving treatment." 

The findings were published on December 18, 2023, in CMAJ. 

'Critical Missed Opportunities' 

The researchers conducted a retrospective, population-based, serial cross-sectional study to examine community-based OAT initiation in Ontario. They drew data from ICES, the Canadian Institute for Health Information Discharge Abstract Database, and other sources to examine emergency department or hospital visits for opioid toxicity between January 1, 2013, and March 31, 2020. The researchers defined community-based OAT initiation as a new prescription filled for methadone, buprenorphine-naloxone, or slow-release oral morphine from a community-based pharmacy. 

"To exclude patients who received slow-release oral morphine for pain rather than for OAT, we included only those who were initiated on daily dispensed therapy," wrote the authors, explaining that a 2018 Canadian clinical practice guideline recommends buprenorphine-naloxone "as first-line treatment to reduce the risk of toxicity and facilitate safer take-home dosing." Methadone and slow-release oral morphine are recommended as second- and third-line options, respectively.

Among 47,910 emergency department visits or hospital admissions for opioid toxicity in Ontario during the study period, 20,702 (43.2%) events among 14,053 patients (median age, 35 years) met inclusion criteria. The primary reasons for exclusion were previous claims for OAT within 30 days of the index visit (17.9%) and no documented OUD diagnosis in the preceding 5 years (24.8%).

The 20,702 OUD events included 5219 hospital admissions and 15,483 emergency department visits. In all, 215 hospital admissions and 636 emergency department visits led to OAT initiation within 7 days of discharge. A secondary analysis showed that the rate of readmission or return outpatient or emergency department visits within 7 days of initial discharge following an OUD event was 22.1%. 

"This is the timeframe associated with very high mortality risk after an overdose," said Hu. "Despite this connection to healthcare services, these patients did not receive OAT, which highlights the critical missed opportunities to engage patients in treatment to prevent future mortality and morbidity related to opioid use."

Of the 379 OAT prescribers whom the researchers identified, most were male (70.2%) general practitioners (67.6%) with a median age of 46 years, who had been practicing for at least 10 years (73.9%). 

Hu suggested that the reasons for underprescribing OAT are probably multifactorial, but they are based in lack of resources and training. "Having the time to properly assess a patient and counsel regarding OAT initiation is important, but time constraints have increasingly become the norm in an overburdened healthcare system," she said. "There is a crisis in family medicine at this time — both a critical shortage of family physicians and increasing workloads and patient volumes — leading to burnout and physicians leaving the workforce." 

She added that although there has been a movement in medical schools over the past few years to incorporate more education about substance use and treatment, "there are no mandatory clinical addictions rotations in many medical schools in Canada. We can see the vast majority of OAT prescriptions in our study were by physicians with more than a decade of experience. We need to ensure that all graduates have clinical experience and are comfortable with recognizing and treating OUD. However, I don't think this is solely in the hands of family physicians. Emergency room physicians and internists frequently see opioid overdoses in their practice and may be the first point of contact in the healthcare system for many unattached patients, given the shortage of family physicians."

'Deplorably Low Rates' 

Commenting on the findings for Medscape Medical News, Michael-John Milloy, PhD, associate professor of medicine at the University of British Columbia (BC) and a research scientist at the BC Centre on Substance Use, both in Vancouver, said that the study "is a timely and important examination of the missed clinical opportunities that contribute to the United States's and Canada's ongoing catastrophe of opioid-related morbidity and mortality, especially among structurally marginalized people who use drugs."

Milloy was not involved in the research. Referring to the observed rate of OAT administration, he said, "This rate, consistent with others from the United States, almost 10 years into the current overdose crisis, reflects the failure of clinical systems of care to respond to overdose risk and reveals that 95% of overdoses, instead of being an opportunity to begin life-saving medication for OUD treatment, are actually missed opportunities to avert future morbidity and mortality."

The "deplorably low rates — even during a public health catastrophe — reveal not only the need to improve care for people living with OUD in acute care settings, but also how far medical systems in Canada must go to provide effective evidence-based care for people with substance use disorders," he added. 

Although strong clinical evidence from randomized trials "supports the use of medication for OUD to prevent fatal overdose as well as other opioid-related harms, including HIV acquisition, the clinical effectiveness of these medications is limited by patient-level factors (eg, concerns over possible side effects, incomplete adherence) and primarily by social or structural barriers to optimal engagement (eg, patient criminalization, anti–drug-user stigma in healthcare settings, suboptimal dosing, and administrative requirements). Nevertheless, improving low rates of medication for OUD initiation adherence and engagement has been identified as a critical and urgent need to address the ongoing overdose crisis," said Milloy.

These data also should be considered in the context of ongoing debates about the most effective strategies for responding to the overdose epidemic, he continued. "The findings clearly reveal that strategies solely reliant on clinical interventions are insufficient in the short term without substantial improvement to adequately respond to rising levels of opioid morbidity and mortality. Community-based interventions to reduce the risks associated with exposure to the unregulated drug supply, especially harm reduction–based interventions that provide alternatives to that supply, are urgently needed now while clinical pathways for people with OUD are established and improved."

Commenting on the study's limitations, Milloy noted that "the data are largely silent on the likely multifactorial reasons underlying low rates of initiation in acute care settings. Future research, especially studies that include people with lived experience as co-investigators, are needed to identify points of necessary improvement along the clinical pathway. Critically, urgent studies are needed to identify behavioral and social or structural factors that promote the initiation of medication for OUD. As always, interventions targeting the social or structural determinants of health, especially for special risk populations, will provide additional benefits for those most risk."

The study was funded by a Canadian Institutes of Health Research grant and was supported by ICES. Hu reported no relevant conflicts. Milloy disclosed that his university receives salary support for him from the US National Institute on Drug Abuse. He is a member of the Canadian Research Initiative in Substance Misuse, a federally funded substance use research consortium, but was not involved in the creation of its 2018 opioid use disorder guidelines.

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.



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