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How do opioids affect the brain?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Dec 29, 2021.

Official answer



  • Opioids bind to and activate opioid receptors on nerve cells in the brain and spinal cord (central nervous system) and other parts of the body (for example, the gastrointestinal tract).
  • Overall, opioids (narcotic painkillers) work by reducing nerve excitability that leads to the sensation of pain. This occurs in the spinal cord leading to the brain.
  • Opioids can also lead to a relaxed sensation, feeling of pleasure and a "high" or euphoric feeling because they also work in the limbic system, which controls our emotions.
  • When opioids block receptors in the brain stem, this can lead to slowed breathing, reduce coughing and further reduction in pain sensation. Slower breathing, called respiratory depression, can be dangerous or even fatal in an overdose.

In general, opioids are prescribed for more severe types of pain like severe injury or trauma, after major surgery, and for cancer pain that may not respond to other pain treatments. When possible, they should be used on a short-term basis due to the risk for misuse, overdose and death.

Common types of opioid receptors include the mu, delta, and kappa receptors. These receptors help to block the release of excitatory neurotransmitters like substance P that are involved with pain. The mu opioid receptor is the main site of action for the most common opioids such as morphine, heroin, fentanyl, and methadone.

Opioids can make people feel relaxed and “high”, which is why they are often abused. Large amounts of dopamine, a "feel good" neurotransmitter, are released throughout the body' reward system, which may reinforce repeated use of the drug and can lead to addiction.

  • Some prescription opioids are stronger than others, but over time you can develop a tolerance to them and may need a higher dose to treat the same level of pain.
  • Some patients with ongoing pain are dependent on opioids and require medical support to stop treatment.
  • Drug addiction is a complex brain disease that involves uncontrollable drug seeking behavior and harmful actions.

Central nervous system side effects from opioids can include drowsiness, sedation, confusion, and slowed breathing, which can lead to hypoxia (low oxygen supply to tissue and brain), coma, or death in the most severe cases.

Opioids can lead to overdose, respiratory depression and death, even when prescribed by a doctor. Naloxone (Narcan, Narcan Nasal, Kloxxado) can be given to help reverse an opioid overdose.

Related: Know Your Naloxone: Save a Life

Some of the most common opioids prescribed for pain in the U.S. are:

In addition to treating pain, opioids are also found in some cough suppressants, to treat diarrhea and to help combat narcotic addiction itself.

Learn more: Which painkiller should you use?

Bottom Line

  • Opioids bind to and activate opioid receptors on nerve cells in the brain, spinal cord (central nervous system) and other parts of the body.
  • When opioids attach to certain receptors, they block pain signals sent from the body to the brain.
  • Dopamine, a neurotransmitter often called the "feel good" neurotransmitter, is released in the body and may reinforce repeated drug use and eventual addiction.

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