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Naloxone facts

What is naloxone?

Effects of naloxone

Further information


pdficon_small Download the Naloxone fact sheet [PDF: 227KB]

Please note: The information given on this page is not medical advice and should not be relied upon in that way. Individuals wanting medical advice about naloxone should consult a health professional.

What is naloxone? 

Naloxone hydrochloride (trade name Narcan®) is a drug that can reverse opioid overdose. It can also be used to treat respiratory depression during pain management or after an anaesthetic.1

It works by blocking opioid drugs, such as heroin and methadone, from attaching to opioid receptors in the brain.1

How is it used?

Naloxone can be injected intravenously (into a vein) or intramuscularly (into a muscle) by medical professionals, such as paramedics. It can also be administered by family and friends of people who use opiates. Speak with your doctor or general practitioner for more information.

It can also be taken as a nasal spray; however, naloxone nasal spray is not registered for use in Australia at this time.

Opioid overdose response plan

Who can administer naloxone?

Naloxone can be administered by authorised medical personnel such as ambulance officers. As of 1 February 2016, naloxone can be purchased over the counter at pharmacies and chemists as a prefilled syringe known as Naloxone Minijet®. Please note, there is currently a shortage of naloxone mini-jets, however, naloxone remains available in ampoule form.

Effects of naloxone

Naloxone cannot be used to get 'high', so it has no potential for misuse.

There is no evidence that extended use of naloxone can cause harmful physical effects or dependence. People who take naloxone do not develop a tolerance to its effects and there have been no reported deaths from naloxone overdose.1

Side effects

The following side effects may be experienced:

  • Nausea and vomiting
  • Wheezy breathing
  • Chest tightness
  • Intense rash with itching
  • High blood pressure
  • Irregular heartbeat
  • Seizures
  • Acute allergic reaction with swelling of the face, lips, tongue and throat2

Naloxone and overdose

People who have been revived with naloxone after overdosing may experience a strong urge to take more opioid drugs, especially if they are addicted to these drugs.

Taking opioid drugs after naloxone is very dangerous because naloxone only stays in the body for a short period of time (1 to 1.5 hours) whereas heroin and other opioid drugs stay in the body for much longer. The effects of sustained-release opioids like OxyContin® and MS Contin® can last for over 12 hours, so naloxone will wear off long before the opioid has left the system. This means that taking more opioids after taking naloxone could cause a second overdose.3

Further information


Reducing the risks


– Find further credible research and information on naloxone.  

ADIN – Find other credible websites and apps on naloxone.


1. Anex. (2010). Lifesavers: a position paper on access to Naloxone Hydrochloride for potential opioid overdose witnesses.

2. Upfal, J. (2006). The Australian drug guide. (7th ed.). Black Inc: Collingwood.

3. International Overdose Day. (n.d.). Overdose basics.

Last updated: 31 August 2016

Information you heard is intended as a general guide only. This audio is copyrighted by the Australian Drug Foundation. Visit for more