Last updated : October 2, 2018

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.

Who can administer naloxone?

Naloxone can be administered by authorised medical personnel such as ambulance officers. It  can also be purchased over the counter at pharmacies or via prescription as an ampoule or pre-filled five dose syringe. Read more about overdose prevention and the administration of naloxone.

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 opioid overdose

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

Taking opioid drugs after naloxone is very dangerous. 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

Naxolone statistics

Naloxone successfully reversed 23 opioid overdoses between 2011 and 2013, during a peer administration trial in Canberra5.

In Australia in 2009, there were 563 accidental deaths attributed to opioids among people aged 15-54 years. In the over 55 age group, there were 70 deaths. Many of these deaths were due to multiple drugs being taken including prescription opioids6

  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.
  4. Australian Institute of Health and Welfare. (2013). National Opioid Pharmacotherapy Statistics Annual Data Collection 2012 [PDF:2MB].
  5. Olsen, A., McDonald, D., Lenton, S., & Dietze P. (2014). Key interim findings : Independent evaluation of the ‘Implementing Expanding Naloxone Availability in the ACT (I-ENAACT)’ program, 2011-2013, Canberra: ACT Health.
  6. Roxburgh, A., & Burns, L. (2014). Accidental opioid-induced deaths in Australia 2010, Sydney: National Drug and Alcohol Research Centre (NDARC).


allergic reaction, high blood pressure, intense rash, irregular heart beat, nausea, reverse opioid overdose, seizures, vomiting.