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Is methadone an opiate blocker?

Medically reviewed by Carmen Pope, BPharm. Last updated on June 7, 2023.

Official answer

  • Yes, methadone can be considered as an opiate blocker.
  • Methadone works by preferentially binding to the mu-opioid receptor, preventing other opioids, such as heroin or morphine, from also binding to this receptor.
  • Methadone-maintained patients who attempt to override methadone with heroin or another narcotic will not experience a “high” nor are they unlikely to experience adverse effects, such as respiratory depression.

Methadone is a long-acting synthetic opioid that may be used to treat opioid addiction and chronic pain. It helps reduce withdrawal symptoms for people who have become addicted to narcotics, such as heroin, and satisfies cravings without producing a high.

How does methadone work?

Methadone works by binding to opiate receptors in the brain. These are the same receptors that other opioids, such as heroin, morphine, and oxycodone activate.

Methadone binds primarily or exclusively to the mu type of opiate receptor to a greater extent than morphine or most other opioids that prefer the mu receptor. By occupying this receptor, methadone prevents other opioids from also binding to it. Put simply, methadone blocks the effects of other opioids.

In addition, a daily dose of methadone creates a methadone “reservoir” in the tissues of the body, which helps keep plasma levels of methadone at a more even level. Having constant and steady blood levels of methadone also helps to block the effects of any short-acting opioids, such as heroin or morphine, that may be taken in addition to methadone.

This makes it difficult for people on methadone treatment to “override” the effects of methadone with heroin to experience a “high” or any other opiate effects. Research has shown that the administration of street doses of heroin, morphine, or hydromorphone to methadone-maintained patients, produces no narcotic-like effects. Studies have also demonstrated that the margin of safety for respiratory depression is very high, and individuals attempting to override the effects of methadone are also unlikely to suffer any adverse effects.


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