A medication that blocks opioid receptors rather than activating them.
In the context of addiction treatment:
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Naloxone is a fast-acting antagonist used to reverse overdoses.
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Naltrexone is a longer-acting antagonist used to treat opioid or alcohol use disorders by blocking the effects of opioids and reducing cravings.
What to know:
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Antagonists can precipitate withdrawal if given to someone with opioids already in their system.
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Naltrexone requires an opioid-free period before starting.
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Antagonists are part of some abstinence-based recovery strategies.
Example:
Someone who has been off opioids for several weeks receives a monthly naltrexone injection to help prevent relapse to opioid use.