Last published: July 19, 2024

Drug Alert

18/07/24 There is concern that protonitazene is now present in illicit oxycodone tablets in the community.

02/07/24 A white powder sold in Melbourne as cocaine contains the potent opioid in ‘protonitazene’.

Protonitazene is a novel synthetic opioid that can produce life-threatening toxic effects in very small amounts.

29/05/24 Four people have been hospitalised across Sydney with severe opioid overdose caused by nitazenes.

People who thought they were taking etazene were taking a more potent nitazene (protonitazepyne*) and a potent novel benzodiazepine (bromazolam).

18/05/24 A granular brown powder sample tested at CanTEST was found to contain N-pyrrolidino protonitazene, a potent synthetic opioid that is stronger than other opioids, including fentanyl.


Due to the lack of formal research about the use and effects of nitazenes, some of the information provided below is based on anecdotal user reports.

What are nitazenes?

Nitazenes are strong synthetic opioids. Opioids include any drug that acts on opioid receptors in the brain, and any natural or synthetic drugs that are derived from, or related to, the opium poppy.

Nitazenes were developed by researchers around 60 years ago as an alternative to morphine, but because of their high potential for overdose were never released.2 Nitazenes have been connected to a number of overdose deaths worldwide.

What do nitazenes look like?

Nitazenes are sold as a white powder, crystalline solid, or brown/yellow powder. They have also been found in tablets (fake oxycodone), heroin, ketamine and synthetic cannabinoids.2,3

Other names

benzimidazole opioids, synthetic opioids, New Psychoactive Substances (NPS)

Some common nitazenes include:

  • isotonitazene
  • metonitazene
  • etonitazene
  • protonitazene.

How are nitazenes used?

Nitazenes can be injected, inhaled, or swallowed (tablet form).2

Effects of nitazenes

Use of any drug can have risks. It’s important to be careful when taking any type of drug.

Nitazenes affect everyone differently, based on:

  • size, weight and health
  • whether the person is used to taking it
  • whether other drugs are taken around the same time
  • the amount taken
  • the strength of the drug (varies from batch to batch).

Short term effects of nitazenes include:

  • euphoria
  • relaxation, drowsiness and clumsiness
  • pain relief
  • reduced stress
  • itchiness
  • nausea and vomiting
  • fever and sweating
  • slow breathing and heart rate.4


If the dose is too high, you might overdose. Call an ambulance straight away by dialling triple zero (000) if you or someone you are with has any of these symptoms:

  • slow/shallow breathing
  • bluish/greyish lips and complexion
  • passing out
  • coma
  • death.5

Ambulance officers do not have to involve the police.

The potency of nitazenes varies between drugs in the class. They can range from levels similar to morphine, to a lot stronger than fentanyl.6,7

If overdose occurs, naloxone will likely temporarily reverse the drug’s effects, including respiratory depression. More than one dose may be required.6

Long-term effects

The long-term effects of nitazenes haven’t been studied enough to understand what the risks might be, but it’s thought they may be like other opioids.

Some common long-term effects of opioids include:

  • increased tolerance
  • dependence
  • constipation
  • damage to vital organs such as the lungs, brain and heart.

Tolerance and dependence

Nitazenes have a high potential for tolerance and dependence.8

Mixing nitazenes and other drugs

The effects of taking nitazenes with other drugs – including over-the-counter or prescribed medications – can be unpredictable and dangerous.

Because of a lack of formal research around mixing nitazenes with other substances, this information covers mixing other substances with opioids in general:

Low risk

  • Opioids + cannabis: Mixing these drugs can work together to increase effects, so while the risk is low there is still a possible risk.

Caution required

  • Opioids + MDMA/LSD: Unlikely to cause interaction. Don’t use Tramadol and MDMA together due to risk of seizures.


  • Opioids + nitrous oxide: Can cause impaired coordination, memory loss and passing out.
  • Opioids + GHB/GBL/benzodiazepines/alcohol: Can cause difficulty breathing, passing out, vomiting and possible death.
  • Opioids + ketamine: Can cause nausea, vomiting, passing out, and possible death.
  • Opioids + cocaine/ice/speed: Increases the risk of heart strain. The stimulant effect of cocaine increases heart rate, and the opioid decreases heart rate. Depending on the amount taken there is a risk of respiratory arrest or heart problems if one wears off before the other.9,10,11

More on Polydrug use

Polydrug use is a term for the use of more than one drug or type of drug at the same time or one after another. Polydrug use can involve both illicit drugs and legal substances, such as alcohol and medications.


Reducing harm

Start with a low dose. Try a small amount first to see how you are affected. It’s important to remember if you are swallowing the drug, it will take longer to take effect than other methods such as injecting. This means there may be more time to get medical help if needed.

Avoid using alone. Have a sober person around who is able to help if needed.

Have naloxone available. Strong opioids like nitazenes may need more than one dose to reverse an overdose.

Avoid taking nitazenes with other substances, in particular other opioids such as heroin. Also avoid depressant drugs like alcohol, GHB, and benzodiazepines.

If you aren't sure if someone is overdosing, call triple zero and request an ambulance. Do not leave the person alone. Ambulances are not required to involve the police.13

Withdrawal from nitazenes

Giving up nitazenes after using them for a long time is challenging because the body has to get used to functioning without them.

Reports from people who use nitazenes suggest that the withdrawal from nitazenes is comparable to a severe opioid withdrawal.

Reported effects include:

  • excessive sweating
  • restless legs
  • fever
  • dizziness
  • flu-like symptoms
  • blackouts
  • anxiety
  • panic attacks.14,15

Getting help

If your use of nitazenes is affecting your health, family, relationships, work, school, financial or other life situations, or you’re concerned about a loved one, you can find help and support.

Call the National Alcohol and Other Drug Hotline on 1800 250 015 for free and confidential advice, information and counselling about alcohol and other drugs

Help and Support Services search

Find a service in your local area from our list. Simply add your location or postcode and filter by service type to quickly discover help near you.

If you're looking for other information or support options, send us an email at


Not sure what you are looking for?
Try our intuitive Path2Help tool and be matched with support information and services tailored to you.

Find out more
Image of a woman walking through a maze

Nitazenes are considered New Psychoactive Substances (NPS) and the laws surrounding NPS are complex, constantly changing and differ between states/territories, but in general they are increasingly becoming stronger.

In Queensland, New South Wales, South Australia and Victoria there is now a ‘blanket ban’ on possessing or selling any substance that has a psychoactive effect other than alcohol, tobacco and food.

In other states and territories in Australia, specific NPS substances are banned and new ones are regularly added to the list. This means that a drug that was legal to sell or possess today, may be illegal tomorrow. The substances banned differ between these states/territories.

  1. John Hopkins Medical. What are opioids? n.d. [cited: 03.01.2022].
  2. World Health Organization. Critical review report: Protonitazene draft 2022.
  3. FRANK. Synthetic Opioids n.d. [cited: 30.05.2022].
  4. High Alert Drug Information and Alerts Aotearoa New Zealand. What are nitazenes? 2023 [cited: 05.06.2023].
  5. Upfal J. Australian drug guide : the plain language guide to drugs and medicines of all kinds. Melbourne, Vic.: Black Inc.; 2016 [cited: 06.2021].
  6. Roberts A, Korona-Bailey J, Mukhopadhyay S. Notes from the Field: Nitazene-Related Deaths — Tennessee, 2019–2021. Morbidity and Mortality Weekly Report (MMWR) [Internet]. 2022 [cited: 31.05.2023].
  7. NSW Health. Warning issued after potent opioid (nitazene) found in heroin 2022 [cited: 06.06.2023].
  8. Drug Enforcement Administration Diversion Control Division Drug & Chemical Evaluation Section. Benzimidazole-Opioids Other Name: Nitazenes 2022 [cited: 05.06.2023].
  9. Hi-Ground. Opioids n.d. [cited: 05.01.2022].
  10. Harm Reduction Victoria. Opioids n.d. [cited: 05.01.2022].
  11. Psychonaut Wiki. Opioids 2022 [cited: 05.01.20022].
  12. World Health Organisation. Lexicon of Alcohol and Drug Terms. World Health Organisation; 1994.
  13. Australian Injecting & Illicit Drug Users League. Nitazenes Nitty-Gritty: What are Nitazenes? And why are they being found in heroin and ketamine in Australia?2023 [cited: 08.06.2023].
  14. World Health Organization. Critical review report: Etonitazepyne (N-pyrrolidinoetonitazene).
  15. Advisory Council on the Misuse of Drugs. ACMD advice on 2-benzyl benzimidazole and piperidine benzimidazolone opioids. 2023.

Explore opioids on the Drug Wheel

Drug wheel segment - Opioids segment@2x.png


coma , death , euphoria , itching , nausea , passing out , relaxation , shallow breathing