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Systematic (IUPAC) name
Clinical data
Trade names Narcan, Evzio
AHFS/ monograph
  • AU: B1
  • US: C (Risk not ruled out) [1]
Legal status
  • AU: S4 (Prescription only)
  • UK: POM (Prescription only)
Routes of
Endotracheal, intranasal, IV, IM
Pharmacokinetic data
Bioavailability 2% (Oral, 90% absorption but high first-pass metabolism)
Metabolism Liver
Onset of action 2 min (IV), 5 min (IM)[1]
Biological half-life 1–1.5 h
Duration of action 30 to 60 min[1]
Excretion Urine, Biliary
CAS Number 465-65-6 YesY
ATC code V03AB15
PubChem CID: 5284596
DrugBank DB01183 YesY
ChemSpider 4447644 YesY
KEGG D08249 YesY
Synonyms 17-allyl- 4,5α-epoxy- 3,14-dihydroxymorphinan- 6-one
Chemical data
Formula C19H21NO4
Molecular mass 327.38 g·mol−1
 N (what is this?)  (verify)

Naloxone, also known as Narcan among other names, is a medication used to reverse the effects of opioids especially in overdose.[1] Naloxone may be combined within the same pill as an opioid to decrease the risk of misuse. When given intravenously it works within two minutes and when injected into a muscle it works within five minutes.[1] The medication may also be used in the nose.[2] The effects of naloxone last about half an hour to an hour.[3] Multiple doses may be required as the duration of action of most opioids is greater than that of naloxone.[1]

Administration to opioid-dependent individuals may cause symptoms of opioid withdrawal including restlessness, agitation, nausea, vomiting, a fast heart rate and sweating. To prevent this, small doses every few minutes can be given until the desired effect is reached. In those with previous heart disease further heart problems have occurred.[1] It appears to be safe in pregnancy after having been given to a limited number of women.[4] Naloxone is a pure opioid antagonist. It works by reversing the depression of the central nervous system and respiratory system caused by opioids.[1]

Naloxone was patented in 1961 by Jack Fishman, Mozes J. Lewenstein, and the company Sankyo. The drug was approved for opioid overdose by Food and Drug Administration in 1971.[5] It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.[6] Naloxone is available as a generic medication and is not very expensive.[1][7] Its wholesale price is between 0.50 and 5.30 USD per dose.[8]

Medical uses[edit]

Opiate overdose[edit]

Naloxone is useful both in acute opioid overdose and in reducing respiratory or mental depression due to opioids.[1]

It is included as a part of emergency overdose response kits distributed to heroin and other opioid drug users, and this has been shown to reduce rates of deaths due to overdose.[9] A prescription for naloxone is recommended if a person is on a high dose of opioid (>100 mg of morphine equivalence/day), is prescribed any dose of opioid accompanied by a benzodiazepine, or is suspected or known to use opioids nonmedically.[10] Prescribing naloxone should be accompanied by standard education that includes preventing, identifying, and responding to an overdose; rescue breathing; and calling emergency services.[11]

Preventing opioid abuse[edit]

Naloxone may be combined with a number of opioids, including buprenorphine and pentazocine, so that when taken orally just the opioid has an effect; but if misused by injecting or taken in large doses, the naloxone blocks the effect of the opioid.[1][12] This combination is used in an effort to prevent abuse.[12]


In a meta-analysis of people with shock, including septic, cardiogenic, hemorrhagic, or spinal shock, those who received naloxone had improved blood flow. The authors of the meta-analysis recommend further study and randomized trials to determine the suitability of naloxone as a treatment for shock.[13]

Naloxone is also experimentally used in the treatment for congenital insensitivity to pain with anhidrosis, an extremely rare disorder (one in 125 million) that renders one unable to feel pain, or differentiate temperatures.[citation needed]

Naloxone can also be used as an antidote in overdose of clonidine, a medication which lowers blood pressure.[14]

Side effects[edit]

Naloxone has little to no effect if opioids are not present. In people with opioids onboard, it may cause increased sweating, nausea, restlessness, trembling, vomiting, flushing, headache, and has in rare cases been associated with heart rhythm changes, seizures, and pulmonary edema.[15][16]

Naloxone has been shown to block the action of pain-lowering endorphins which the body produces naturally. These endorphins likely operate on the same opioid receptors that naloxone blocks. Naloxone is capable of blocking a placebo pain-lowering response, both in clinical and experimental pain, if the placebo is administered together with a hidden or blind injection of naloxone.[17] Other studies have found that placebo alone can activate the body's μ-opioid endorphin system, delivering pain relief via the same receptor mechanism as morphine.[citation needed]

Special populations[edit]

Pregnancy and breast feeding[edit]

Naloxone is pregnancy category B or C in the United States.[1] Studies in rodents given a daily maximum dose of 10 mg naloxone showed no harmful effects to the fetus, although human studies are lacking and the drug does cross the placenta, which may lead to the precipitation of withdrawal in the fetus. In this setting, further research is needed before safety can be assured, so naloxone should only be used during pregnancy if it is a medical necessity.[18]

It is currently unknown if naloxone is excreted in breast milk.

Kidney and liver dysfunction[edit]

Currently, no established clinical trials have been conducted in patients with insufficient kidney function or liver disease, and as such, these patients should be monitored closely if naloxone is clinically indicated.


Naloxone has an extremely high affinity for μ-opioid receptors in the central nervous system (CNS). Naloxone is a μ-opioid receptor (MOR) competitive antagonist, and its rapid blockade of those receptors often produces rapid onset of withdrawal symptoms. Naloxone also has an antagonist action, though with a lower affinity, at κ- (KOR) and δ-opioid receptors (DOR). Unlike other opioid receptor antagonists, naloxone is essentially a pure antagonist with no agonist properties. If administered in the absence of concomitant opioid use, no functional pharmacological activity occurs (except the inability for the body to combat pain naturally). In contrast to direct opiate agonists, which elicit opiate withdrawal symptoms when discontinued in opiate-tolerant patients, no evidence indicates the development of tolerance or dependence on naloxone. The mechanism of action is not completely understood, but studies suggest it functions to produce withdrawal symptoms by competing for opiate receptor sites within the CNS (a competitive antagonist, not a direct agonist), thereby preventing the action of both endogenous and xenobiotic opiates on these receptors without directly producing any effects itself.[19]

The Ki affinity values of (−)-naloxone for the MOR, KOR, and DOR have been reported as 0.559 nM, 4.91 nM, and 36.5 nM, respectively, whereas for (+)-naloxone, 3,550 nM, 8,950 nM, and 122,000 nM, respectively, have been reported.[20] As such, (−)-naloxone appears to be the active isomer.[20] Moreover, these data suggest that naloxone binds to the MOR with approximately 9-fold greater affinity relative to the KOR and around 60-fold greater affinity relative to the DOR.[20]


When administered parenterally (non-orally or non-rectally, e.g. intravenously or by injection), as is most common, naloxone has a rapid distribution throughout the body. The mean serum half life has been shown to range from 30 to 81 minutes, shorter than the average half life of some opiates necessitating repeat dosing if opioid receptors must be stopped from triggering for an extended period. Naloxone is primarily metabolized by the liver. Its major metabolite is naloxone-3-glucuronide which is excreted in the urine.[19]


Naloxone is most commonly injected intravenously for fastest action, which usually causes the drug to act within a minute, and last up to 45 minutes. It can also be administered via intramuscular or subcutaneous injection. Finally, a wedge device (nasal atomizer) attached to a syringe may be used to create a mist which delivers the drug to the nasal mucosa,[21] was FDA approved in 2015 it is more common outside of clinical facilities.[22] [23]

The individual is closely monitored for signs of improvement in respiratory function and mental status. If minimal or no response is observed within 2–3 minutes dosing may be repeated every 2 minutes until the maximum dose of 10 mg has been reached. If there is no response at this time alternative diagnosis and treatment should be pursued. If patients do show a response they should remain under close monitoring as the effects of naloxone may wear off before those of the opioids and they may require repeat dosing at a later time.

Naloxone can be used orally along with Oxycontin Controlled Release, and helps in reducing the constipation associated with opioids. Enteral administration of naloxone blocks opioid action at the intestinal receptor level, but has low systemic bioavailability due to marked hepatic first pass metabolism.[24]

In April 2014, the US Food and Drug Administration (FDA) approved Evzio, a hand-held automatic injector naloxone product that is pocket-sized and can be used in non-medical settings such as in the home. It is designed use by laypersons such as family members and caregivers of opioid users at-risk for an opioid emergency, such as an overdose.[25] The approval process was fast-tracked as one initiative to reduce the death toll caused by opiate overdoses. At the time of approval, an estimated 16,000 annual deaths were attributed to prescription opioid overdoses in the US.[26]

Society and culture[edit]


The patent for naloxone has expired. It is available in generic forms. Trade names include: Narcan, Nalone, Evzio, Prenoxad Injection, Narcanti, and others.

Legal status[edit]

In the US, naloxone is classified as a prescription medication, though it is not a controlled substance.[27] While it is legal to prescribe naloxone in every state, dispensing the drug by medical professionals (including physicians or other licensed prescribers) at the point of service is subject to rules that vary by jurisdiction.

While paramedics have carried naloxone for decades, law enforcement officers in many states throughout the country carry naloxone to reverse the effects of heroin overdoses when reaching the location prior to paramedics. As of July 12, 2015, law enforcement departments in 28 states carry naloxone to quickly respond to opioid overdoses.[28]

Prehospital access[edit]

Laws in many states have been changed in recent years to allow wider distribution of naloxone.[29][30] Several states have also moved to permit pharmacies to dispense the medication without the patient first seeing a physician or other non-pharmacist professional.[31] Over 200 naloxone distribution programs utilize licensed prescribers to distribute the drug, often through the use of standing medication orders [32][33] whereby the medication is distributed under the medical authority of a physician or other prescriber (such as a pharmacist under California's AB1535.

Following the use of the nasal spray device by police officers on Staten Island in New York, an additional 20,000 police officers will begin carrying naloxone in mid-2014. The state's Office of the Attorney General will provide US$1.2 million to supply nearly 20,000 kits and Police Commissioner William Bratton said: "Naloxone gives individuals a second chance to get help".[34]

A survey of US naloxone prescription programs in 2010 revealed that 21 out of 48 programs reported challenges in obtaining naloxone in the months leading up to the survey, due mainly to either cost increases that outstripped allocated funding, or the suppliers' inability to fill orders.[35] The approximate cost of a 1 ml ampoule of naloxone in the US is estimated to be significantly higher than in most Western countries.[32]

Projects of this type are under way in many North American cities.[35][36][37] CDC estimates the US programs for drug users and their caregivers prescribing take-home doses of naloxone and training on its use are estimated to have prevented 10,000 opioid overdose deaths.[35] Healthcare institution-based naloxone prescription programs have also helped reduce rates of opioid overdose in North Carolina, and have been replicated in the US military.[32][38] Programs training police and fire personnel in opioid overdose response using naloxone have also shown promise in the US and effort is increasing to integrate opioid fatality prevention in the overall response to the overdose crisis.[39][40][41][42][43] Pilot projects were also started in Scotland in 2006. Also in the UK, in December 2008, the Welsh Assembly government announced its intention to establish demonstration sites for take-home naloxone.[44]


Naloxone is the INN, BAN, USAN for the medication.

The CAS number of naloxone is 465-65-6; the anhydrous hydrochloride salt has CAS 357-08-4 and the hydrochloride salt with 2 molecules of water, hydrochloride dihydrate, has CAS 51481-60-8.


2013 documentary film Reach for Me: Fighting to End the American Drug Overdose Epidemic interviews people involved in naloxone programs aiming to make naloxone available to opioid users and pain patients.[45]

See also[edit]


  1. ^ a b c d e f g h i j k l "Naloxone Hydrochloride". The American Society of Health-System Pharmacists. Retrieved Jan 2, 2015. 
  2. ^ Roberts, James R. (2014). Roberts and Hedges' clinical procedures in emergency medicine (6 ed.). London: Elsevier Health Sciences. p. 476. ISBN 9781455748594. 
  3. ^ Bosack, Robert (2015). Anesthesia Complications in the Dental Office. John Wiley & Sons. p. 191. ISBN 9781118828625. 
  4. ^ "Prescribing medicines in pregnancy database". Australian Government. 3 March 2014. Retrieved 22 April 2014. 
  5. ^ Yardley, William (14 December 2013). "Jack Fishman Dies at 83; Saved Many From Overdose". New York Times. Retrieved 2015-07-06. 
  6. ^ "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014. 
  7. ^ Hamilton, Richard J. (2013). Tarascon pocket pharmacopoeia : 2014 classic shirt-pocket edition (28 ed.). Sudbury: Jones & Bartlett Learning. p. 174. ISBN 9781284053982. 
  8. ^ "Naloxone HCL". International Drug Price Indicator Guide. Retrieved 13 August 2015. 
  9. ^ Maxwell S, Bigg D, Stanczykiewicz K, Carlberg-Racich S (2006). "Prescribing naloxone to actively injecting heroin users: a program to reduce heroin overdose deaths". J Addict Dis 25 (3): 89–96. doi:10.1300/J069v25n03_11. PMID 16956873. 
  10. ^ Lazarus P (2007). "Project Lazarus, Wilkes County, North Carolina: Policy Briefing Document Prepared for the North Carolina Medical Board in Advance of the Public Hearing Regarding Prescription Naloxone". Raleigh, NC. [page needed][verification needed]
  11. ^ Bowman S, Eiserman J, Beletsky L, Stancliff S, Bruce RD (July 2013). "Reducing the health consequences of opioid addiction in primary care". Am. J. Med. 126 (7): 565–71. doi:10.1016/j.amjmed.2012.11.031. PMID 23664112. 
  12. ^ a b Orman, JS; Keating, GM (2009). "Buprenorphine/naloxone: a review of its use in the treatment of opioid dependence.". Drugs 69 (5): 577–607. doi:10.2165/00003495-200969050-00006. PMID 19368419. 
  13. ^ Boef, B; Poirier V; Gauvin F; Guerguerian AM; Roy C; Farrell CA; Lacroix J (2003). "Naloxone for shock.". Cochrane Database Syst Rev. (4): CD004443. doi:10.1002/14651858.CD004443. PMID 14584016. 
  14. ^ Niemann, JT. "Reversal of clonidine toxicity by naloxone". Retrieved 22 March 2015. 
  15. ^ "Naloxone Side Effects in Detail". Retrieved 5 May 2015. 
  16. ^ Schwartz JA, Koenigsberg MD (November 1987). "Naloxone-induced pulmonary edema". Ann Emerg Med 16 (11): 1294–6. doi:10.1016/S0196-0644(87)80244-5. PMID 3662194. 
  17. ^ Sauro MD, Greenberg RP (February 2005). "Endogenous opiates and the placebo effect: a meta-analytic review". J Psychosom Res 58 (2): 115–20. doi:10.1016/j.jpsychores.2004.07.001. PMID 15820838. 
  18. ^ Sobor, M; Timar, J.; Riba, P.; Kiraly, KP. (2013). "Behavioural studies during the gestational-lactation period in morphine treated rats". Neuropsychopharmacol Hung 15 (4): 239–251. PMID 24380965. 
  19. ^ a b "NALOXONE HYDROCHLORIDE injection, solution". Daily Med. Retrieved 21 April 2014. 
  20. ^ a b c Codd EE, Shank RP, Schupsky JJ, Raffa RB (September 1995). "Serotonin and norepinephrine uptake inhibiting activity of centrally acting analgesics: structural determinants and role in antinociception". J. Pharmacol. Exp. Ther. 274 (3): 1263–70. PMID 7562497. 
  21. ^ Wolfe TR, Bernstone T (April 2004). "Intranasal drug delivery: an alternative to intravenous administration in selected emergency cases". J Emerg Nurs 30 (2): 141–7. doi:10.1016/j.jen.2004.01.006. PMID 15039670. 
  22. ^ Fiore, Kristina. "On-Label Nasal Naloxone in the Works". MedPage Today. Retrieved 2015-07-20. 
  23. ^ "FDA Approves Narcan Nasal Spray". Retrieved 2015-11-21. 
  24. ^ Meissner W, Schmidt U, Hartmann M, Kath R, Reinhart K (January 2000). "Oral naloxone reverses opioid-associated constipation". Pain 84 (1): 105–9. doi:10.1016/S0304-3959(99)00185-2. PMID 10601678. 
  25. ^ FDA News Release. "FDA approves new hand-held auto-injector to reverse opioid overdose". Retrieved 2015-07-20. 
  26. ^ Brady Dennis (3 April 2014). "FDA approves device to combat opioid drug overdose". The Washington Post. Retrieved 8 April 2014. 
  27. ^ 21 U.S.C.A. §§801-904; see e.g., LA Rev Stat. Ann. §40:964 (specifically excluding Naloxone from the schedule of controlled substances.)
  28. ^ "US Law Enforcement Who Carry Naloxone". North Carolina Harm Reduction Coalition. Retrieved 12 July 2015. 
  29. ^ Corey Davis. "Legal interventions to reduce overdose mortality: Naloxone access and overdose good samaritan laws" (PDF). Network for Public Health Law. 
  30. ^ Davis CS, Webb D, Burris SC (2013). "Changing Law from Barrier to Facilitator of Opioid Overdose Prevention". Journal of Law, Medicine and Ethics. 
  31. ^ Ryan Oftebro, "Kelley-Ross Pharmacy provides Take-Home Naloxone to prevent opioid overdose", Kelley-Ross, August 20, 2013
  32. ^ a b c Beletsky L, Burris SC, Kral AH (2009). "Closing Death's Door: Action Steps to Facilitate Emergency Opioid Drug Overdose Reversal in the United States". SSRN Electronic Journal. doi:10.2139/ssrn.1437163. 
  33. ^ Burris SC, Beletsky L, Castagna CA, Coyle C, Crowe C, McLaughlin JM (2009). "Stopping an Invisible Epidemic: Legal Issues in the Provision of Naloxone to Prevent Opioid Overdose". SSRN Electronic Journal. doi:10.2139/ssrn.1434381. 
  34. ^ Jessica Durando (27 May 2014). "NYPD officers to carry heroin antidote". USA Today. Retrieved 30 May 2014. 
  35. ^ a b c "Community-Based Opioid Overdose Prevention Programs Providing Naloxone — United States, 2010". Centers for Disease Control and Prevention 61 (6): 101–5. December 2010. PMID 22337174. 
  36. ^ "OD Prevention Program Locator". Overdose Prevention Alliance. Retrieved 15 May 2012. 
  37. ^ Karissa Donkin (9 September 2012). "Toronto naloxone program reduces drug overdoses among addicts". The Toronto Star. Retrieved 5 May 2015. 
  38. ^ Albert S, Brason FW, Sanford CK, Dasgupta N, Graham J, Lovette B (June 2011). "Project Lazarus: community-based overdose prevention in rural North Carolina". Pain Med. 12 Suppl 2: S77–85. doi:10.1111/j.1526-4637.2011.01128.x. PMID 21668761. 
  39. ^ Beletsky L, Rich JD, Walley AY (November 2012). "Prevention of fatal opioid overdose". JAMA 308 (18): 1863–4. doi:10.1001/jama.2012.14205. PMC 3551246. PMID 23150005. 
  40. ^ Beletsky L, Moroz E. "The Quincy Police Department: Pioneering Naloxone Among First Responders.". Overdose Prevention Alliance. Retrieved 15 May 2012. 
  41. ^ Lavoie D (April 2012). "Naloxone: Drug-Overdose Antidote Is Put In Addicts' Hands". Huffington Post. 
  42. ^ Davis CS, Beletsky L (2009). "Bundling occupational safety with harm reduction information as a feasible method for improving police receptiveness to syringe access programs: evidence from three U.S. cities". Harm Reduct J 6 (1): 16. doi:10.1186/1477-7517-6-16. PMC 2716314. PMID 19602236. 
  43. ^ "2013 National drug control strategy" (PDF). 2013. 
  44. ^ "IHRA 21st International Conference Liverpool, 26th April 2010 - Introducing 'take home' Naloxone in Wales" (PDF). Retrieved 9 March 2011. 
  45. ^ Reach for Me: Fighting to End the American Drug Overdose Epidemic

External links[edit]