Opioid Use Disorder

Opioid use disorder (OUD) is a chronic, treatable illness in which medication can reduce withdrawal, craving, illicit opioid use and fatal overdose. In the 2024 Canadian national guideline, buprenorphine and methadone are co-equal first-line opioid agonist treatment options; slow-release oral morphine is a second-line option when first-line treatment is ineffective or not tolerated. The older hierarchy that placed buprenorphine/naloxone above methadone as the universal preferred option no longer applies. Treatment should not wait for a perfect psychosocial plan, complete abstinence or a negative urine drug screen. Psychosocial care can be offered as a supplement, but it must not be mandatory before medication is provided. Harm reduction, including naloxone, overdose education and safer-use support, is part of OUD treatment. The most time-sensitive prescribing decision is induction. Standard same-day buprenorphine/naloxone must begin after moderate-to-severe opioid withdrawal is established. Fentanyl exposure can make elapsed time since last use an unreliable guide, so an individualized low-dose overlapping protocol may be considered. Methadone requires low-dose initiation and slow titration because drug accumulation can cause respiratory depression before the patient reaches steady state.