Opioid Intoxication

Opioid Intoxication occurs when there is a clinically significant problematic behavioural or psychological change (e.g. - initial euphoria followed by apathy, dysphoria, psychomotor agitation or retardation, impaired judgment) that develops during, or shortly after ingestion.[1] Opioid intoxication can progress into a severe overdose resulting in death.

  • Opioid intoxication can result in death.
    • In the United States, in 2018, opioids were involved in 46,802 overdose deaths (69.5% of all drug overdose deaths).[2]
    • In Canada, over a four year period 2016 and 2020, 17,602 Canadians are thought to have died from an opioid toxicity death.[3]
  • Opioid intoxication can be deadly, as individuals can progress to respiratory depression, coma, and death.
  • The main risks of opioid toxicity respiratory depression. More rarely, there can be seizures, acute respiratory/lung injuries, and adverse cardiac events.
Risk Factors
  • Males, younger age, using opioids alone, and escalating doses are risk factors for opioid intoxication.
Criterion A

Recent use of an opioid.

Criterion B

Clinically significant problematic behavioural or psychological changes (e.g. - initial euphoria followed by apathy, dysphoria, psychomotor agitation or retardation, impaired judgment) that developed during, or shortly after, opioid use.

Criterion C

Pupillary constriction (or pupillary dilation due to anoxia from severe overdose) and at least 1 of the following signs or symptoms developing during, or shortly after, opioid use:

  1. Drowsiness or coma
  2. Slurred speech
  3. Impairment in attention or memory
Criterion D

The signs or symptoms are not attributable to another medical condition and are not better explained by another mental disorder, including intoxication with another substance.

Severity Specifier

Specify if:

  • With perceptual disturbances: This specifier may be noted in the rare instance in which hallucinations with intact reality testing or auditory, visual, or tactile illusions occur in the absence of a delirium.
  • Common signs and symptoms include euphoria, respiratory and CNS depression, decreased gag reflex, pupillary constriction (pinpoint pupils), and seizures.
  • Individuals with opioid intoxication may have inattention to the environment to the point of ignoring potentially harmful or life-threatening events.[4]
  • Opioid receptors are located throughout the brain, spinal cord, and gastrointestinal tract.
  • Opioid receptors are abundant in the respiratory control centres, which the brainstem and higher centres including the insula, thalamus, and anterior cingulate cortex.
  • In overdose, opioids alter the rhythm generation of breathing and respiratory drive
    • These changes in the respiratory pattern can lead to severe respiratory depression and death.
  • Other substance intoxication
    • Alcohol intoxication and sedative-hypnotic intoxication can resemble opioid intoxication. A diagnosis of alcohol or sedative-hypnotic intoxication can be made on the absence of pupillary constriction or the lack of a response to a naloxone challenge. In some cases, intoxication may be due a combination of both opioids and alcohol (or other sedatives). In these cases, naloxone will only partially reverse the sedative effects.
  • Other opioid-related disorders
    • Opioid intoxication is different from the other opioid-induced disorders (e.g. - opioid-induced depressive disorder, with onset during intoxication) because the symptoms in opioid-induced depressive disorder (and other induced disorders) predominate in the clinical presentation and meet full criteria for the relevant disorder.
  • Other medical conditions
    • Other medical conditions can mimic opioid toxicity, including diabetic ketoacidosis, metabolic disturbances (hypercalcemia, hypernatremia), neurological diseases (meningitis), and adverse reactions to medications.
  • A general emergency medicine approach to investigations should be employed in the investigations for suspected opioid intoxication/overdose, including blood glucose, urine drug screen, a complete blood cell count (CBC), comprehensive metabolic and electrolytes, creatine kinase, and arterial blood gas (if respiratory compromise).
  • Imaging studies such as neuroimaging (e.g. - if suspecting a head injury), or chest x-ray (e.g. - if suspecting lung injury) should be ordered as clinically indicated.
  • A routine physical examination includes looking for any new needle track marks, pinpoint pupils, signs of respiratory distress (dyspnea, wheezing), and signs of severe hypotension.
  • Nausea and vomiting is also typically present
  • The clinician should also look for any signs of airway obstruction (e.g. - from vomitus)
  • Attending to vital life signs, airway, breathing, and circulation is the most important first step.
    • In severe respiratory depression, the individual may require intubation.
  • Naloxone is the emergency treatment of choice and should be administered as soon as possible if there is high clinical suspicion for an opioid overdose.
    • Naloxone can be administered via intravenous, intramuscular, subcutaneous, or intranasal routes.
  • Post-naloxone administration, the individual can become combative or violent, and use of restraints may be required.

Opioid Use Disorder Guidelines

Guideline Location Year PDF Website
Canadian Medical Association Journal (CMAJ) Canada 2018 - Link
BC Centre on Substance Use (BCCSU) Canada 2023 Link Link
META:PHI Canada 2019 Link Link
Canadian Guidelines on Opioid Use Disorder Among Older Adults Canada 2020 PDF Link
National Institute for Health and Care Excellence (NICE) UK 2007 - Link
American Psychiatric Association USA 2006, 2007 - Guideline (2006)
Guideline Watch (2007)
Quick Reference
For Patients
For Providers
1) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.
4) American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders (5th ed.). Arlington, VA.