Last updated : April 8, 2019

What is naloxone?

Naloxone hydrochloride (brand names Prenoxad, Nyxoid) is a drug that can temporarily reverse opioid overdose. It works by blocking opioid drugs, such as heroin and oxycodone, from attaching to opioid receptors in the brain.

How is it used?

Naloxone can be injected intramuscularly (into a muscle) or delivered by intranasal spray. It may be administered by medical professionals, such as paramedics, as well as family, friends, or bystanders in an emergency where someone is experiencing an overdose.

Best practice is to provide a person who might be administering naloxone with training. See the bottom of this page for information on where to find training providers.
Read more about overdose prevention and the administration of naloxone .

Effects of naloxone

The effects of naloxone are to temporarily block opioid receptors and prevent opioid drugs from working. 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

Most side effects from naloxone are mild. However, if someone is opioid-dependent and they are given a high dose of naloxone, it can bring on symptoms of opioid withdrawal such as:

  • Nausea and vomiting
  • Sweating
  • Trembling
  • Nervousness
  • Fast pulse

In rare cases, even a person who is not opioid-dependent might experience:

  • An allergic reaction with symptoms such as swelling of the face, lips, tongue and throat, wheezy breathing, chest tightness, intense rash with itching
  • High blood pressure
  • Irregular heartbeat
  • Seizures

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 dependent.

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

More information

For information about naloxone training and accessibility in your state or territory, get in touch with peak harm minimisation bodies or check the Pennington Institute to find out what local service providers are delivering training.


Western Australia

New South Wales


Northern Territory

Australian Capital Territory

  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.