Nitazenes: Signs of overdose and how to respond

What are nitazenes?

Nitazenes (sometimes called ‘zines’ or ‘zenes’) are a class of synthetic opioids developed in the 1950s but never approved as medicines due to the high risk of overdose. 

Some common nitazenes include metonitazene, protonitazene, isontonitazine and etonitazene. These can vary in strength (, but some nitazenes can be 50 times stronger than fentanyl and 100–500+ times stronger than heroin or morphine. 

Nitazenes are cheaper and easier to manufacture than natural opium-based drugs such as heroin or morphine. There is increasing evidence that nitazenes are entering the global drug supply and contributing to growing rates of harm. 

Because nitazenes are extremely potent at very low doses, they can easily lead to overdose – especially when taken with other opioid or non-opioid depressant drugs.  

Signs of a nitazene overdose 

Nitazenes, like all opioids, slow the central nervous system and breathing. Too much can stop the natural reflex to breathe, which may result in brain injury or death. 

Signs of overdose may include: 

• Not responding / cannot be woken 

• Irregular, shallow, or slow breathing (less than 12 breaths per minute) 

• Snoring or gurgling sounds (may appear like deep sleep) 

• Blue, pale, grey or ashen lips or fingertips 

• Limp body and cold or clammy skin 

• Possible vomiting 

How to respond to a nitazene overdose 

Opioid overdoses can take hours to become fatal. Even if a person appears to be “sleeping,” they may be in danger. Never leave someone to sleep it off. Immediate action could save a life. 

Before you act, check for danger (sharp objects, chemicals, traffic, etc.). 

Check for vital signs: 

A – Alert: Not responding to voice, touch or pain 

B – Breathing: Noisy, shallow, slow, stopped or unusual snoring/gurgling sounds 

C – Colour: Blue or pale lips and fingertips (lighter skin) or grey/ashy colouring (darker skin) 

Try to wake the person by calling their name, squeezing their shoulder firmly or rubbing knuckles firmly across the sternum (chest bone). 

• If there is no response but the person is breathing: Place them in the recovery position. Ensure their airway is open and continue monitoring breathing and colour. 

• If the person is not breathing: Use naloxone (Narcan®) if available and/or start rescue breathing. 

Call an ambulance, follow instructions and stay on the line. Do not leave the person alone. 

Using naloxone (Narcan) 

• Assemble the naloxone according to packet instructions. 

• Give the smallest dose possible and record the time. Keep packaging and provide it to paramedics. 

• Wait 2–4 minutes and stay with the person. 

• If the person has not started breathing, give another dose and/or start rescue breathing (2 breaths every 5 seconds). 

• If breathing resumes, place the person in the recovery position and continue monitoring until help arrives. 

Important: Naloxone only temporarily reverses opioid overdose and will not reverse other drug effects. Because nitazenes can be very strong, additional doses may be required. 

Never leave the person alone as they may stop breathing again once naloxone wears off. 

Rescue breathing (if naloxone is not available) 

• Lay the person on their back and support their head. 

• Tilt their head back to open the airway. 

• Clear any obstruction. 

• Pinch their nose and create a mouth-to-mouth seal. 
• Give 2 quick breaths every 5 seconds, watching for a rise in the chest (not the stomach).