What Is an Opioid Antagonist?

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  • Written By: C. Webb
  • Edited By: Daniel Lindley
  • Last Modified Date: 01 April 2020
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An opioid antagonist is a drug that binds itself to receptors in the brain and blocks the ability of the brain to respond to opiate use. Some drugs used are partial antagonists, while others provide full antagonist effects. An opioid antagonist is often used to combat addiction to opiates.

The antagonist is stronger than an opiate and prevents the opiate from binding to receptors. Though the binding ability is strong, the antagonist is unable to produce the enhanced endorphins that use of an opiate causes. This inability is what makes an opioid antagonist a successful treatment for opiate addiction. An addict's brain is seeking the endorphin rush. The endorphin rush is not possible with an antagonist.

Naltrexone and naloxone are two examples of full opioid antagonists. Partial opioid antagonists include levallorphan and nalorphine. They are called partial antagonists because of the withdrawal symptoms they produce in people who have recently used opiates.

The partial opioid antagonist is used in treating addiction by having the addict ingest a prescribed amount each day. Cravings are blocked, and the ability to ingest opiates is eliminated because doing so can throw the body into full opiate withdrawal. A full opioid antagonist is typically used to flush opiates out of the system. Overdose cases are typically treated with naloxone or naltrexone.


Opiate addicts in residential rehabilitation facilities are often started on an opioid antagonist to block opiate withdrawal symptoms, which otherwise can become severe. Some facilities slowly wean the addict to a reduced dose and then move him or her completely off the drug. Others give a smaller dose and then set the addict up with an aftercare specialist who will continue to prescribe the drug for the addict and monitor its use and progress.

Naltrexone is one opioid antagonist capable of reversing the long-term brain chemistry changes experienced by those with a history opiate abuse. Possible brain chemistry changes caused by continued abuse of opiates include anxiety and depression. Proper use of an antagonist reverses such chemistry and restores the brain to its pre-addiction state. This process can take 18 to 24 months.

The treatment of depersonalization disorder can also include the use of an opioid antagonist. Symptoms of depersonalization include feelings of detachment and of living in a dream world. Research concluded a consistent low dose of naloxone eliminated or significantly reduced depersonalization symptoms. Another study only found a 30-percent improvement in symptoms.


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