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What is an Opioid Antagonist?

By Zawn Villines
An opioid antagonist can help treat opioid addiction and reverse an opioid overdose in some cases.

Opioid addiction is a leading cause of overdose death. In 2019 alone, opioid-related overdoses claimed 49,860 lives--and this figure comprised more than 70% of all drug overdose deaths, according to the Centers for Disease Control and Prevention (CDC). Opioid antagonists can save lives by treating opioid addiction and, in some cases, may reverse or prevent an overdose. 

What do Opioid Antagonists Do?

Opioid drugs bind to specific opioid receptors in the brain and nervous system. Opioid antagonists block or reduce the effects of opioids by preventing opioids from binding to one or more groups of opioid receptors, according to a 2021 StatPearls article. Certain approved forms of these medications are therefore used in medication-assisted treatment programs for opioid use disorder, such as Naltrexone.

Opioid antagonists can help you quit using opioids by reducing the rewards associated with the drugs. They can also help prevent or reverse a life-threatening opioid overdose in certain circumstances. Naloxone (or Narcan), another opioid antagonist, is an over-the-counter spray medication that was developed specifically for use by laypersons to administer to others in the case of a suspected opioid overdose. 

Read on for more details about each of these important medications. 

Naltrexone, An Opioid Antagonist

Naltrexone is a synthetic opioid that binds to opioid receptors in the nervous system. The Substance Abuse and Mental Health Services Administration (SAMHSA) notes that this medication binds to and blocks opioid receptors and reduces or suppresses opioid cravings. 

“Naltrexone has a stronger affinity for the mu opioid receptors than opioids,” Ellena Boddie, MD, a board-certified internist who treats addiction, tells WebMD Connect to Care. “It works by immediately displacing the opioids from the opioid receptors.”

The U.S. Food and Drug Administration (FDA) has approved naltrexone for the treatment of both alcohol and opioid use disorders. It works by reducing the high and pleasure you get from using opioids, and it prevents physiological dependence on opioids as well. Because it also stimulates opioid receptors, it can help minimize opioid withdrawal symptoms when you quit using. 

Naloxone, An Opioid Antagonist

Naloxone, sold under the brand name Narcan, is an opioid antagonist that can help reverse an opioid overdose. An opioid overdose can cause fatal respiratory depression and may also cause a host of other long and short-term side effects

“If you immediately administer naloxone, it will cross the blood-brain barrier, and then it displaces the opioid from the mu receptors. This immediately improves breathing and makes the patient more alert,” Boddie says.

The brand-name version of naloxone, Narcan, is a nasal spray that requires no training to use or administer. According to the CDC, bystanders are present during 40% of opioid-related deaths. Therefore, high numbers of people carrying naloxone on them, especially those with loved ones abusing opioids, could significantly reduce overdose deaths. 

Don’t Wait. Get Help Now.

If you or a loved one are struggling with addiction, WebMD Connect to Care Advisors are standing by to help.