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Opioids are a family of medications used to treat severe pain. When used as prescribed, opioids are an effective medication, however they can also carry a greater risk of addiction because of the “high” they can produce. You can develop a tolerance to opioids which means you need to take more of the drug to get the wanted effect. This increases the risks of addiction and overdose.


Examples of opioids include:

  • Oxycodone
  • Morphine
  • Hydromorphone
  • Fentanyl
  • Codeine
  • Methadone
  • Heroin

What do opioids look like?

Prescription opioids come in various forms.

  • Pills
  • Patches
  • Sprays
  • Syrups
  • Solutions
  • Suppositories

Who uses opioids?

Opioids are prescribed by physicians to people with acute or chronic pain resulting from disease, surgery or injury. Because of the risk of abuse, opioids are prescribed cautiously for chronic pain. Between 2010 and 2014, the number of prescription opioids legally dispensed in Canada climbed almost 24 percent with more than 21.7 million prescriptions dispensed last year. Opioid misuse is the third leading cause of accidental death in Ontario.

How do opioids make you feel?

The way opioids affect you depends on many factors, including:

  • how much you use
  • how often and how long you use opioids
  • how you take them (e.g., by injection, orally)
  • your mood, expectations and environment
  • your age
  • whether you have certain pre-existing medical or psychiatric conditions
  • whether you’ve taken any alcohol or other drugs

Low doses of opioids decrease the sensation of pain and the emotional response to pain. They may also produce euphoria, drowsiness, relaxation, difficulty concentrating, constricted pupils, a slight decrease in breathing rate, nausea, vomiting, constipation, loss of appetite and sweating.

With higher doses, these effects are more intense and last longer. The speed and intensity of the effects of opioids vary depending on how the drugs are taken. When taken by mouth, the effects come on gradually, and are usually felt in about 10 to 20 minutes. When injected into a vein, the effects are most intense and are felt within a minute.

How long does the feeling last?

When opioids are taken to relieve pain, the duration of the effect varies somewhat depending on the type of opioid taken. For many opioids, a single dose can provide pain relief for four to five hours.


What's happening in London?

London has multiple overlapping drug-related crises that require a range of layered responses.

Learn more →

Evaluation of London's Temporary Overdose Prevention Site

Saving Lives. Changing Lives. Findings from an Evaluation of London's Temporary Overdose Prevention Site

Comprehensive Report (PDF)

Summary Report (PDF)

Issue Note - Drug Crisis

Download the briefing note to learn more about how the Health Unit is working to address the drug crisis in London.

Download (PDF)

Business Case for Supervised Consumption in London, Ontario

Report provided to the Middlesex-London Board of Health - September 2018

Download (PDF)

Siting of Supervised Consumption Facilities

Report to City of London Planning and Environment Committee - April 30, 2018

Download (PDF)

Community Consultation Report on Supervised Consumption Facilities

Download (PDF)


Are opioids dangerous?

Opioids can be dangerous if they are used without medical supervision. Here are some of the reasons:

  • Opioids are depressant drugs, which means that they slow down the part of the brain that controls breathing.
  • People who use opioids regularly for their pleasurable effects soon develop tolerance to these effects, which means they need to use more and more of the drug to achieve the desired effect. As the amount taken increases, so does the risk of overdose. If people with tolerance stop taking the drug, they lose their tolerance. If they then resume taking the same amount they took before they stopped, the risk of overdose is extreme.
  • Some people inject opioids to increase the intensity of the euphoric effect. Reusing needles and sharing needles carries a high risk of infection and disease (e.g., HIV, hepatitis). When pharmaceutical tablets or capsules are dissolved for injection, non-drug substances contained in these products can permanently damage veins and organs.

Are opioids addictive?

Addiction is when a drug becomes central to a person’s thoughts, emotions and activities, and he or she feels a craving or compulsion to continue using the drug despite negative consequences. This may or may not include physical dependence.
Like all medications, opioids have benefits and risks. When opioids are used as directed under medical supervision in the general population, they are considered effective and their side effects (drowsiness, nausea, constipation, etc.) are generally manageable. However, the risk of addiction appears to be higher in people with a history of abuse, addiction or psychiatric concerns.

Date of creation: October 3, 2017
Last modified on: May 21, 2019


1Centre for Addiction and Mental Health, 2010. Do You Know...Prescription Opioiods. Retrieved from