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Summary sheet: Naloxone
Chemical Nomenclature
Common names Naloxone, Narcan, Evzio
Substitutive name 1-N-Allyl-14-hydroxynordihydromorphinone
Systematic name (4R,4aS,7aR,12bS)-4a,9-Dihydroxy-3-prop-2-enyl-2,4,5,6,7a,13-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-7-one
Class Membership
Psychoactive class Opioid (Antagonist)
Chemical class Morphinan
Routes of Administration

WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.

Threshold 4 mg
Light 4 - 8 mg
Common 8 - 16 mg
Strong 16 - 28 mg
Heavy 28 mg +
Total 1 - 2 hours
Onset 5 - 15 minutes
Come up 20 - 40 minutes
Peak 1 - 2 hours
Offset 30 - 60 minutes
After effects 1 - 12 hours

Common 1 - 4 mg
Total 30 - 60 minutes
Onset 0 - 10 minutes

Common 0.4 - 2 mg
Total 30 - 60 minutes
Onset 0.25 - 2 minutes
Common 0.4 - 2 mg
Total 30 - 60 minutes
Onset 0.25 - 2 minutes

DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.


Naloxone (commonly sold under the brand names Narcan and Evzio) is a synthetic mu-opioid antagonist of the morphinan chemical class that is widely used to reverse the effects of an acute opioid overdose. Naloxone is sold under the brand name Narcan as a nasal spray and Evzio as an auto-injector with voice instructions.

Naloxone has been credited with saving an unprecedented number of opioid overdose victims.[1] This is partially due to naloxone programs in several countries to give naloxone to people who use opioids along with the rapid deployment of naloxone by law enforcement agencies and emergency medical services. Many emergency responders and law enforcement are trained to administer naloxone to reverse the effects of opioid overdoses immediately.

Besides its use in emergency medicine, naloxone has been researched in the treatment of depersonalization disorder with promising results.[2]


Naloxone, also known as N-allylnoroxymorphone or as 17-allyl-4,5α-epoxy-3,14-dihydroxymorphinan-6-one, is a synthetic morphinan derivative and was derived from oxymorphone (14-hydroxydihydromorphinone), an opioid analgesic.[3] Naloxone is a racemic mixture of two enantiomers, (–)-naloxone (levonaloxone) and (+)-naloxone (dextronaloxone), only the former of which is active at opioid receptors.[4] The drug is highly lipophilic, allowing it to rapidly penetrate the brain and to achieve a far greater brain to serum ratio than that of morphine.[3]

The chemical half-life of naloxone is such that injection and nasal forms have been marketed with 24-month and 18-month shelf-lives, respectively. A 2018 study noted that the nasal and injection forms presented as chemically stable to 36- and 28-months, respectively, which prompted an as yet incomplete five year stability study to be initiated. This suggests that expired caches of material in community and healthcare settings may still be efficacious substantially beyond their labeled expiration dates.[5]


Naloxone acts as a potent μ-opioid receptor inverse agonist. Because of its high affinity for the μ-opioid receptor, it knocks other ligands out of the receptor. If naloxone is administered without previous administration of opioids, it has few biological effects, notably a lower pain threshold.[citation needed]

Naloxone has two isomers, (+)naloxone and (-)naloxone, with the latter being active. The liver metabolizes naloxone. It has very low oral bioavailability, which is why it is administered intravenously, intramuscularly or intranasally. Small amounts of naloxone are often added to opioids like buprenorphine and pentazocine to prevent abuse. This is because of the bioavailability difference; injecting the isolated ingredients from the pill will also inject naloxone.

Naloxone has been noted to block a placebo based analgesic effect. For example, if an individual has been administered something that they were told was morphine and had an analgesic response to it, naloxone will block that response.[6]

Naloxone also has a lower affinity as an antagonist at the κ-opioid and δ-opioid receptors.

If naloxone is 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 people, 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.[7]

Subjective effects

When taken by itself and outside the context of an opioid overdose, naloxone causes relatively comfortable sedation and general suppression of emotions.

Disclaimer: The effects listed below cite the Subjective Effect Index (SEI), an open research literature based on anecdotal user reports and the personal analyses of PsychonautWiki contributors. As a result, they should be viewed with a healthy degree of skepticism.

It is also worth noting that these effects will not necessarily occur in a predictable or reliable manner, although higher doses are more liable to induce the full spectrum of effects. Likewise, adverse effects become increasingly likely with higher doses and may include addiction, severe injury, or death ☠.

Physical effects

Cognitive effects

Experience reports

There are currently no anecdotal reports which describe the effects of this compound within our experience index. Additional experience reports can be found here:


When administering naloxone, it is important to understand which formulation it is coming in and what that means. In the United States, naloxone primarily comes in four formulations. Narcan is a prescription nasal spray that is inserted and administered into the nose. Evzio is an autoinjector with voice instruction capabilities similar to many epinephrine autoinjectors. Naloxone may come in a pink or orange box that reads "Naloxone Hydrochloride, INJ., USP" or a green box that reads the same thing. The main difference between these two is that the green ones come with a needle built in and is meant for intramuscular injection specifically.

The three most common types of naloxone. Narcan, Evzio and generic orange/pink box naloxone respectively.

Common Brands (United States)

Narcan is one of the most common brands containing naloxone. To use it, these steps are followed:

1) Peel the device out of the packaging
2) Hold the device with the thumb on the bottom of the plunger and 2 fingers on the nozzle
3) Place and hold the tip of the nozzle in either nostril until one's fingers touch the bottom of the patient’s nose
4) Press the plunger down, which will release the medication.

Narcan is not a substitute for professional medical care. On brand Narcan will deliver 4mg of naloxone. Narcan does not last as long as many opioids, so before or after administering Narcan, one should call for emergency services.

Evzio is one of the most common brands containing naloxone. To use it one can follow these steps: 1) Pull the device out of the case 2) Pull off the red safety guard 3) Place the black end of the device against one's outer thigh 4) Ensure there are no solid objects between the black end and their skin -- the needle can go through clothes if necessary 5) Press firmly down on the device until distinct click is heard and hold it there for 5 seconds to ensure all the naloxone is released from the device.

Evzio is not a substitute for professional medical care. Evzio does not last as long as many opioids, so before or after administering Evzio, one should call for emergency services.

To use orange/pink box naloxone, one can follow these steps: 1) Take the device out of the box 2) If the device is not assembled, assemble it 3) Remove the yellow caps off the cylinder 4) On the narrow end, put the cylindrical cap 5) Take the vial of the medication and put it into the chamber, with the colored end pointing towards the patient 6) The dosage for adults is 2 mg of naloxone and the device comes with 2 mg 7) Put the device in either nostril and press down on the vial of medication until half of it is dispersed into that nostril 8) Then, take the device and put it in the other nostril and administer the rest of the medication.

If the patient is under 5 years of age, only administer 1 mg total, or a quarter of the total medication in each nostril. Each naloxone should be administered with the goal of restoring ventilation (breathing) but not necessarily consciousness. Naloxone should not be administered in the field to patients under 28 days of age.

Boxed naloxone is not a substitute for professional medical care. Naloxone does not last as long as many opioids. So before or after administering naloxone, one should call for emergency services.

Toxicity and harm potential

Naloxone in the form it is used by emergency medical services and law enforcement.

Naloxone is considered not habit-forming. When naloxone is administered in an opioid overdose, the individual will go through immediate withdrawal. Sudden opioid withdrawal may be life-threatening in extreme cases. Symptoms of opioid withdrawal may include, but are not limited to agitation, nausea, psychosis, temperature regulation suppression, anxiety, physical fatigue, excessive yawning, sweating, dehydration, and pupil dilation.

It has been noted that naloxone may be needed in higher dosages depending on the opioid that was consumed. It is not uncommon for several doses of naloxone to be administered in overdose cases involving fentanyl or one of its many analogs. If an individual does not have opioids in their system when naloxone is administered, it may cause dehydration and nausea.

It is strongly recommended that one use harm reduction practices when using this substance.

Legal status

Throughout the world, naloxone is not considered a controlled substance. It is a prescription drug in most countries.[citation needed]

  • Australia: In Australia, naloxone is considered an over the counter drug and is available at most pharmacies [9]
  • Canada: In Canada, naloxone kits are distributed at many emergency rooms, clinics, and some pharmacies.[citation needed]
  • Germany: Naloxone is a prescription medicine, according to Anlage 1 AMVV.[10]
  • Switzerland: Preparations containing only naloxone are listed as "Abgabekategorie B" pharmaceuticals, which require a prescription to obtain.[citation needed]
  • Turkey: Naloxone is unavailable in Turkey.[11] Also buying medications / drugs from abroad forbidden.
  • United States: At a federal level, naloxone is a prescription drug. Many states have programs that make naloxone over the counter and available at request at most pharmacies. In the United States, most jurisdictions have programs to deploy naloxone to law enforcement and fire and rescue services.[citation needed]
  • United Kingdom: In the United Kingdom, naloxone is considered a prescription drug, but drug services can supply it without a prescription. And anyone can use it to save a life in an emergency.[12]

See also

External links


  1. Community-Based Opioid Overdose Prevention Programs Providing Naloxone — United States, 2010 
  2. Nuller, Y. L., Morozova, M. G., Kushnir, O. N., Hamper, N. (June 2001). "Effect of naloxone therapy on depersonalization: a pilot study". Journal of Psychopharmacology (Oxford, England). 15 (2): 93–95. doi:10.1177/026988110101500205. ISSN 0269-8811. 
  3. 3.0 3.1 Dean, R. L., Bilsky, E. J., Negus, S. S., eds. (2009). Opiate receptors and antagonists: from bench to clinic. Contemporary neuroscience. Humana Press. ISBN 9781588298812. 
  4. Bennett, L. A., ed. (2006). New topics in substance abuse treatment. Nova Science Publishers. ISBN 9781594548314. 
  5. Opioid overdose reversal products chemically stable past expiration date, study indicates: Extended shelf-life has potential for stockpiles and communities, American Association of Pharmaceutical Scientists, 2018, retrieved 8 November 2018 
  6. Sauro, M. D., Greenberg, R. P. (1 February 2005). "Endogenous opiates and the placebo effect: A meta-analytic review". Journal of Psychosomatic Research. 58 (2): 115–120. doi:10.1016/j.jpsychores.2004.07.001. ISSN 0022-3999. 
  7. NALOXONE HYDROCHLORIDE injection, solution, retrieved 21 April 2014 
  8. Nuller, Y. L., Morozova, M. G., Kushnir, O. N., Hamper, N. (March 2001). "Effect of naloxone therapy on depersonalization: a pilot study". Journal of Psychopharmacology. 15 (2): 93–95. doi:10.1177/026988110101500205. ISSN 0269-8811. 
  9. How painkiller use becomes a heroin addiction, 2016 
  10. Anlage 1 AMVV - Einzelnorm 
  12. Widening the availability of naloxone