Safer Using – Nitazenes

About Nitazenes

Nitazenes, also known as benzimidazole opioids, are a class of synthetic opioids which vary widely in potency.1 Some nitazenes, including protonitazene and etonitazene, are more potent than fentanyl and thus pose a very high risk of overdose.1,2 Nitazenes were first synthesised in the late 1950s but never reached the market as medicines.1 Since the early 2010s, synthetic opioids have flooded the drug market in the United States and have significantly contributed to opioid-related overdoses and deaths.2 Beginning in 2019, nitazenes have been detected in forensic laboratories across the United States, Canada, Europe and Australia.2 In 2020, synthetic opioids, including fentanyl and nitazenes, accounted for more than 60% of drug fatalities in the United States.3  

In recent years, nitazenes were found to be present in various heroin samples, counterfeit pills, and other recreational drugs across Australia. In South Australia, protonitazene was linked to one death and multiple overdoses.4 Some of these overdoses resulted from consuming what people thought were GHB and methamphetamine.4 In Queensland, protonitazene was detected in counterfeit Xanax alprazolam pills which may have been linked to two deaths.5 In NSW, nitazenes were detected in counterfeit Kalma alprazolam pills as well as heroin samples.6,7 In the ACT, metonitazene was detected in a counterfeit oxycodone pill.8 In Victoria, protonitazene was detected in a sample sold as ketamine.9 

Even with specialised chemistry equipment, detecting nitazenes in drug samples can be difficult since they are often present in extremely small amounts (e.g., a few milligrams). Unfortunately, fentanyl test strips are unable to detect nitazenes.8 

Nitazene Effects

The effects of nitazenes are similar to other opioids, but they can be anywhere from 2 to 1000 times more potent than morphine.1 The effects of nitazenes can include:1 

  • Pain relief.  
  • Euphoria. 
  • Fatigue and sedation. 
  • Sleepiness and drowsiness. 
  • Nausea and vomiting. 
  • Dizziness. 
  • Confusion.  
  • Slowed breathing.  

The effects of clonitazene typically last 4 or more hours when taken orally.1,10 The duration of effects may differ for other nitazenes and other routes of administration. 

Nitazene Dosing

The active dose depends on the exact nitazene being ingested which is extremely difficult to verify.1 The relative potency of nitazenes compared to morphine is roughly as follows:1 

Etonitazene > isonitazene > protonitazene > metonitazene > etodesnitazene (etazene) > clonitazene > morphine 

5-10 milligrams of oral clonitazene is considered a moderate dose, whereas only 0.25 milligrams of oral etonitazene is sufficient to produce effects.1,10 The strength of the dose also depends on the route of administration, with intravenous, intramuscular, and subcutaneous injection being more potent than oral administration.1  

Nitazene Overdose and Naloxone

Extremely small doses of nitazenes have the potential to cause overdose and death.1 Injecting nitazenes may pose a greater risk of overdose as the lethal dose may be many times smaller than when ingested orally.1 The symptoms of a nitazene overdose can include:1,6,11 

  • Slowed breathing. 
  • Snoring. 
  • Loss of consciousness. 
  • Blue or grey skin, lips, and/or fingernails. 
  • Small pupils. 

Like fentanyl, nitazenes may also cause muscles in the chest to become rigid, which is commonly called “wooden chest”.1 

If you suspect someone has overdosed on an opioid, contact emergency services as soon as possible.   

Naloxone, also known as Narcan, is an opioid receptor antagonist which can temporarily reverse the effects of opioids.1 Naloxone can partially reverse an overdose caused by nitazenes, however, the extreme potency of synthetic opioids means that multiple administrations of naloxone are often required.1,2 Additionally, the effects of synthetic opioids typically last longer than naloxone, so the overdose may return after the naloxone has worn off.1,2 This means it is essential to seek medical attention even if you have already administered naloxone. 

Naloxone is available for free without a prescription in Australia as part of the Take Home Naloxone program.12 Depending on the jurisdiction, it may be available at pharmacies, alcohol and drug treatment centres, needle and syringe programs, among other services.12 Naloxone is available for free at the CAHMA drop-in centre and at CanTEST.  














Written by Darcy Lynch

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