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What's the difference between naltrexone and naloxone?

Medically reviewed by Carmen Pope, BPharm. Last updated on March 30, 2023.

Official answer

by drugclasses.com

Naltrexone and naloxone are both drugs called opioid antagonists. That means these medications bind to opioid receptors in the brain to block the effects of other drugs. Naltrexone is used as part of treatment for opioid or alcohol use disorder. Naloxone is used only to reverse the effects of an overdose quickly.

What is naltrexone?

Naltrexone is a drug used as part of treatment for opioid use disorder. It is given as a long-acting injection prescribed to block the pleasurable (euphoric) and relaxing (sedative) effects of an opioid drug like heroin or morphine. Naltrexone is not an opioid and is not addictive. It does not cause withdrawal symptoms when stopped suddenly.

As long as the drug is taken, the effects of opioids will be blocked and cravings for opioids will be reduced. This may help a person not use opioid drugs while continuing other treatments, like counseling.

Naltrexone may also be used to treat alcohol use disorder. This drug is given as a daily pill or as a long-acting injection. Taking naltrexone daily may reduce cravings for alcohol and help a person maintain sobriety.

Drinking alcohol stimulates the brain to produce endorphins. Endorphins bind to opioid receptors and cause the pleasurable effects of alcohol. When these receptors are blocked by naltrexone, it eliminates the pleasurable effects.

Related questions

What is naloxone?

Naloxone is a short-acting drug used to reverse the effects of an opioid overdose. It can be given as a nasal spray or an injection. Naloxone treatment requires immediate medical intervention to avoid serious opioid withdrawal symptoms. Naloxone can be a life-saving medication for people at risk of an opioid overdose death.

This drug should be given at the first sign of an opioid overdose. Signs of opioid overdose include:

  • Unconsciousness
  • Slow or absent breathing
  • Pinpoint pupils
  • Blue lips or nose.

Naloxone only works against opioids like heroin, fentanyl, morphine or oxycodone. It does not block the effects of drugs like alcohol, tranquilizers, cocaine or amphetamines. If you aren't sure what a person has overdosed on, you should still give Naloxone because it won't cause additional harm.

After using naloxone, long-term treatment, including medical assistance, may be needed. So stay with the person for at least 4 hours or until help arrives.

References
  1. U.S. Department of Health and Human Services, Substance Abuse and Mental Health Services Administration. Naltrexone. March 21, 2023. Available at: https://www.samhsa.gov/medication-assisted-treatment/medications-counseling-related-conditions/naltrexone. [Accessed March 30, 2023].
  2. U.S. Department of Health and Human Services, Substance Abuse and Mental Health Services. Naloxone. January 25th, 2023. Available at: https://www.samhsa.gov/medication-assisted-treatment/medications-counseling-related-conditions/naloxone. [Accessed March 30, 2023].
  3. Lifesaving Naloxone. Centers for Disease Control and Prevention. Jan 25, 2023. https://www.cdc.gov/stopoverdose/naloxone/index.html
  4. Acquiring Naloxone. Law Enforcement Naloxone Toolkit. https://bjatta.bja.ojp.gov/tools/naloxone/Acquiring-Naloxone#:~:text=Naloxone%20is%20a%20prescription%20medication,the%20drug%20by%20first%20responders.

Read next

Should I take naltrexone in the morning or at night?

The manufacturer does not specify if you should take naltrexone tablets in the morning or at night. Take naltrexone exactly as your doctor orders it. Many patients take their medication in the morning to help affirm their continued treatment success for either opioid use disorder or alcohol use disorder. Taking naltrexone tablets after a meal (for example: breakfast) may help to lessen any stomach side effects such as nausea or pain. Continue reading

Does naltrexone cause weight gain?

Weight gain is not a common side effect with oral naltrexone treatment. When used in combination with bupropion, naltrexone is approved to help promote weight loss. Naltrexone is known to frequently cause stomach side effects like nausea and vomiting, stomach pain or cramping, and loss of appetite which could contribute to weight loss. Weight gain and increased appetite have been reported as a possible side effect, but is not common. Continue reading

Acamprosate vs naltrexone: How do they compare?

Acamprosate and naltrexone are two different medications that are used in the treatment of alcohol use disorder. They work in different ways to help people who are dependent on alcohol to abstain from drinking it. Naltrexone is also used for the treatment of opioid use disorder.

Acamprosate was thought to be slightly more effective at helping people with alcohol use disorder remain off alcohol, while naltrexone was thought to be slightly more effective at helping reduce heavy drinking and cravings, according to the results of a meta-analysis which used data from 64 trials.

Results from two small studies, however, indicate that naltrexone is more effective than acamprosate in a number of areas. Continue reading

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