Illicit opioid information
What Is Fentanyl?
Fentanyl is a very potent opioid used medically for severe pain and also found in Canada's illegal drug supply. Non-medical fentanyl use carries a high risk of overdose because potency and contamination can be unpredictable.
Overview
What is Fentanyl?
Fentanyl is a very potent opioid used medically for severe pain and also found in Canada's illegal drug supply. Non-medical fentanyl use carries a high risk of overdose because potency and contamination can be unpredictable.
How it can affect the body
Fentanyl can cause pain relief, drowsiness, slowed breathing, nausea, constricted pupils and changes in consciousness. Effects vary by dose, route, other substances used and individual health factors.
Dependence vs. addiction
Physical dependence means the body has adapted to regular opioid exposure and withdrawal can occur when use stops. Opioid use disorder involves a broader pattern of impaired control and continued use despite harm. A clinician assesses the difference.
Signs of problematic use
- Increasing difficulty controlling opioid use
- Strong cravings or withdrawal symptoms
- Continued use despite health, work or relationship harms
- Needing more opioid to achieve a similar effect
Important health risks
- Respiratory depression and overdose
- Unexpected fentanyl in the unregulated drug supply
- Higher overdose risk when combined with alcohol, benzodiazepines or other sedatives
- Infection and other harms related to injection equipment
When emergency care is needed
A suspected opioid overdose is a medical emergency. Call 911, give naloxone if available, follow dispatcher instructions and stay with the person until help arrives.
How addiction is medically assessed
An addiction-medicine assessment reviews current opioid use, withdrawal, overdose history, medications, medical conditions and treatment goals so a clinician can recommend an appropriate pathway.
Treatment options
Opioid agonist treatment can include Methadone, buprenorphine/naloxone (Suboxone) or slow-release oral morphine when clinically appropriate. The medication is selected by a clinician, not by the webpage.
Treatment pathway
Looking for treatment rather than general information?
The treatment page focuses on how TSCP care works, how to start and what a clinician may consider.
Editorial transparency
Medical sources & review status
Prepared by the TSCP editorial team using Canadian public-health and clinical sources. A named medical reviewer is not displayed until TSCP confirms the reviewer and credentials.
Content updated: 2026-09-10