What is naloxone?

Quick Answer
Naloxone, also known as Narcan, is a synthetic opioid antagonist used as an antidote for opioid overdose. Naloxone reverses the life-threatening respiratory depression caused by natural and synthetic opioids, including heroin, morphine, propoxyphene, and methadone. Naloxone is not a controlled substance and was once only available by prescription. Beginning in 2014 and in response to the growing opiate epidemic in the United States, however, several pharmacies across the country began carrying the drug for sale over-the-counter.
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Naloxone is a pure opioid antagonist that completely displaces narcotics from the opioid receptor sites in the brain's central nervous system. Naloxone is the treatment of choice for emergencies involving opioid overdose and intoxication. It is most often administered intravenously because of the need for a rapid onset of activity, but nasal Naloxone is also effective in reversing the effects of an overdose . Naloxone’s effects are usually seen within two minutes of administration and last for thirty to forty-five minutes. Because opiates have a longer half-life than Naloxone, repeat doses of naloxone may be necessary if complete reversal of opioid intoxication is not achieved.

Naloxone combined with narcotic analgesic Buprenorphine, with the brand name Suboxone, is also used to treat opiate addiction. Suboxone is available through specially licensed physicians as a facet of long-term maintenance therapy for opioid addiction, usually in an outpatient, office-based setting. In rare instances, naloxone may be used postoperatively to reverse the effects of anesthesia.

Naloxone/Narcan distribution programs have been implemented in cities worldwide to provide naloxone to opioid abusers and their acquaintances to be used in the case of an overdose. From 2014–2015, there was a significant increase in the number of first responders in cities and towns throughout the United States who began carrying Narcan. These programs are critical components of harm reduction methodology and in reducing morbidity and mortality associated with opioid abuse.


Naloxone may cause increased heart rate, elevated blood pressure, and pulmonary edema, but these adverse effects do not usually warrant avoiding its use, given the life-threatening nature of opioid overdose. However, naloxone does precipitate immediate withdrawal symptoms in opioid-dependent persons.


Bazazi, A. R., et al. “Preventing Opiate Overdose Deaths: Examining Objections To Take-Home Naloxone.” Journal of Health Care for the Poor and Underserved 21.4 (2010): 1108–13. Print.

Dawson, Andrew H. “Naloxone, Naltrexone, and Nalmefene.” Medical Toxicology. Ed. Richard C. Dart. 3rd ed. Philadelphia: Wolters, 2004. Print.

Fukuda, Kasuhiko. “Opioids.” Miller’s Anesthesia. Eds. Ronald D. Miller, et al. 7th ed. Orlando: Churchill, 2009. Print.

Hedrich, Dagmar, and Richard Hartnoll. "Harm Reduction Interventions." Textbook of Addiction Treatment: International Perspectives. Eds. Nady el-Guebaly, et al. Milan: Springer, 2015. 1291–313. Print.

Mintzer, Ira L., et al. “Treating Opioid Addiction with Buprenorphine-Naloxone in Community-Based Primary Care Settings.” Annals of Family Medicine 5 (2007): 146–50. Print.

Sporer, Karl A., and Alex H. Kral. “Prescription Naloxone: A Novel Approach to Heroin Overdose Prevention.” Annals of Emergency Medicine 49.2 (2007): 17–77. Print.