Nitazenes and fentanyl have been linked to several deaths in New Zealand and a large number of deaths overseas. They are extremely potent in low doses and overdoses occur very quickly. It is important not to use alone and to have naloxone on hand.  

Key things to know

Carry naloxone with you - it can reverse an opioid overdose

Naloxone info

If you think someone is overdosing, call 111 and give them naloxone

Signs of an overdose

They are highly potent, start with a very small 'tester' dose to see how it affects you

Safer using

Crush, mix and measure pills to have better control over the dose you're taking

Safer using

Use drug checking services to make sure you know what type of opioid you have

Drug checking info

How does fentanyl/nitazene make you feel?

Fentanyl and nitazenes are a group of potent synthetic opioids. There are many types of fentanyl, called ‘analogues’ such as carfentanil or paraflurofentanyl. Likewise, there are many different nitazenes such as metonitazene or etonitazene. Newer, stronger analogues appear on the drug market regularly, making them difficult to keep track of. These can vary in strength and potency, but are all active in very low doses, making them difficult to dose safely.  

How long the effects of fentanyl and nitazenes last can depend on which type you use, how you take them (e.g. smoke, inject) and whether they are mixed with alcohol, other drugs, or medicines.  

The effects of fentanyl and nitazenes can come on quickly, especially if they are smoked or injected. How long the effects last can vary depending on which type of fentanyl or nitazene you have, how you take it and your individual body. Overdoses from fentanyl or nitazenes can occur with very small amounts. At any dose you may experience:  

Pleasant effects Unpleasant effects

Physical relaxation


Reduced anxiety

Reduced feelings of physical pain

Feelings of sleepiness

Relief of withdrawal symptoms (if you are dependent on opioids)





Nausea or vomiting

Feeling confused or disoriented

Slowed heartrate

Blue lips and fingers

Pale and clammy skin

Pinpoint pupils

Making snoring or gurgling noises

Shallow or slowed breathing or not breathing at all


Loss of consciousness


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How can you be safer when using fentanyl/nitazene?

WARNING: Overdoses from fentanyl and nitazenes can occur very quickly, and people can rapidly lose consciousness and stop breathing. There is a very small window of time to respond to an opioid overdose 

Have naloxone on hand. Naloxone is a drug that can reverse opioid overdoses. In New Zealand, naloxone comes as a nasal spray called Nyxoid, or in ampules (that are injected). If someone is experiencing an opioid overdose, naloxone can reverse the effects and give you more time to get medical help. You can be prescribed naloxone by a doctor, access it from some needle exchanges or you can buy Nyxoid online from PHARMACO.  

You will likely need at least two doses of naloxone to treat someone overdosing on nitazenes or fentanyl.  

Avoid using alone. Opioid overdoses can happen fast and can be deadly if they are not responded to quickly. If you overdose on an opioid, you won’t be able to call for help, or administer naloxone to yourself. It is a good idea to have a sober buddy around who knows the signs of an opioid overdose and can help you if things go wrong.  

 If someone is overdosing on opioids, it is important to call 111 and then administer naloxone as soon as possible.  

Start with a low dose. There are many types of fentanyl and nitazenes, all of which have different doses and duration of effects. However, they are all active in very low doses, meaning that it is important to start with a very small ‘tester’ dose, to see how it affects you before using more. We recommend avoiding redosing, however if you choose to do so, it is best to wait at least an hour to feel the full effects before taking more* 

*note some nitazenes are thought to last for over 10 hours, so redosing still poses an increased risk, even after 1 hour.  

Get your drugs checked. Fentanyl and nitazenes all have different doses, and they are sometimes sold as something else. It is a great idea to get your drugs checked before you use them. Knowing what type of fentanyl or nitazene you have and if it is mixed with anything else can help you understand how to dose in a safer way.  

Fentanyl and nitazenes are sometimes found in fake pills such as ‘M30s’ or sold as weaker opioids such as morphine. We recommend getting any opioids that are not prescribed to you tested at a drug checking clinic. You can find drug checking clinics in your area here 

Order fentanyl test strips (FTS) from us. It is a good idea to test any substance you think may contain any opioid with fentanyl test strips, which can tell you if your substance contains fentanyl. These strips are easy to use, and you can order these for free on The Level.  

Remember that FTS will not detect Nitazenes or other opioids.  

Crush, mix and measure everything you plan on using. Because fentanyl and nitazenes are very potent in small doses, it is important that you try to distribute the active ingredient as evenly as possible. Otherwise, you can end up with the same ‘dose’ containing very different amounts of the drug - this is called the ‘chocolate chip cookie effect’.  

To reduce the risk of the chocolate chip cookie effect, take these steps:   

  • First, crush any pills, crystals, clumps, or larger pieces in a baggie with the back of a spoon.  

  • Then, shake the baggie vigorously to make sure that it is all combined well, and all parts of the drug look the same  

  • Then measure your dose out. Remember to start with a very low dose first.  

Avoid mixing with alcohol, drugs, or other medicines. Fentanyl and nitazenes are strong depressants, meaning they slow down your brain and body functions. Mixing them with other depressants such as GHB/GBL, alcohol, benzodiazepines or other opioids can increase your risk of unpleasant effects and of losing consciousness or dying. Using with other depressants can also make it harder for naloxone to work if you overdose.  


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What happens if you have too much fentanyl/nitazene?

Fentanyl and nitazenes can cause overdoses in very small amounts. Someone may use these drugs and become unconscious or stop breathing very quickly.  

If someone appears to be drifting off to sleep, or stops responding to you, keep a close eye on them and continue to try and wake them. Speak loudly to them or administer light pain by trying a collarbone knock, a flick or sternum rub (rubbing your fist back and forth in the middle of their breastbone) 

If your symptoms worsen or you are with somebody who 

  • Has very pale or blue skin or fingertips 

  • Has cold and clammy skin  

  • Their body is limp  

  • Has a seizure 

  • Is vomiting  

  • Has pinpoint pupils  

  • Is making snoring, rattling, or gurgling noises  

  • Has shallow, slowed breathing or is not breathing at all  

  • Loses consciousness 

  • Has no pulse  

Call 111. These are signs that someone is overdosing. You or the people around you need to act quickly. Give the person naloxone if you have it.  

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What do comedowns from fentanyl/nitazene feel like, and how can you feel better?

As fentanyl and nitazenes are depressant drugs, they won’t cause a ‘comedown’ in the same way that stimulants like cocaine or MDMA do. However, you can experience after-effects as these drugs wear off.

If you don’t use opioids often, you may feel tired, confused, anxious or have a headache after using fentanyl or nitazenes. These effects don’t last long and are usually gone after a few hours.  

 If you use opioids often, you may have developed a tolerance to them and could experience withdrawal symptoms as the effects wear off. You may feel anxious, sweaty, nauseous, have tremors, and have cravings to use more opioids. You might also feel very agitated, dizzy and in pain. Depending how often you have used fentanyl or nitazenes, these symptoms can last from several days (from last use) to several weeks.   

If you... 

  • Feel dizzy  

  • Feel anxious  

  • Are tired or lethargic  

  • Feel irritable or agitated 

  • Have a headache or a heavy head  

  • Are nauseous  

  • Feel confused or mildly disoriented  

You can try...

  • Get plenty of rest and sleep. 

  • Remember to eat and drink plenty of water. 

  • Get moving to release feel-good brain chemicals. 

  • Reach out and talk with friends and whānau for support. 

  • Relax and do things that you enjoy to take your mind off not feeling well. 

  • Avoid caffeine, alcohol, and other drugs. 

  • Practice mindfulness and deep breathing, and try writing down your thoughts and feelings 

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What are the long-term effects of using fentanyl/nitazene?

Long-term use of fentanyl or nitazenes can have impacts on your brain and body. Using these drugs regularly generally leads to increased tolerance, meaning you need more and more to feel the same effects, or to prevent withdrawal symptoms. The potency of these drugs and how quickly tolerance can develop means that they can difficult to stop using.  

Fentanyl and nitazenes can cause sexual dysfunction, affect the cycles of people who menstruate and cause fertility issues in all genders. These drugs can also cause kidney and liver diseases and increase your chance of developing pulmonary infections. Fentanyl and nitazenes affect your digestive system and often cause chronic constipation, which can lead to bowel obstructions if it is not treated early. They also can affect your bones, which can lead to early onset osteoporosis, more easily broken bones and increased tooth problems.  

Long-term use of fentanyl or nitazenes can affect your brain and your mental health. These potent opioids have been found to deteriorate white matter in your brain, which can lead to memory loss and difficulty controlling your behaviour and emotions. Long term use can also worsen mental health conditions such as depression, anxiety, and schizophrenia. 

While fentanyl and nitazenes can cause long term damage to your body and brain, it is important to remember that many of the long-terms effects can reduce significantly or go away completely after you cut down or stop using these drugs.  

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How do you manage withdrawal from fentanyl/nitazene?

See the 'Making changes' page for more information on how to manage withdrawal from drugs and alcohol.  

As fentanyl and nitazenes are such potent drugs, regular use can quickly result in dependence or tolerance. You may find you need to use more and more to feel the same effects. It also means that it can be very difficult to cut down or take a break from using them.  

Many people find that withdrawal symptoms start quickly after your last dose of fentanyl or nitazenes wears off. How unpleasant the withdrawal symptoms are depends on how long you have used, how much you use and your physical and mental health. Symptoms can last for several weeks from last use, sometimes longer.  

While the symptoms of withdrawal from fentanyl and nitazenes are rarely life-threatening, they are very unpleasant and can be difficult to manage alone. There are things you can do to make the process less challenging, such as going on Opioid Substitution Treatment (OST). OST services will transition you from fentanyl or nitazenes to prescription opioid agonists such as methadone or buprenorphine. People accessing OST often have an easier time stopping their use of fentanyl and nitazenes long-term. You can access OST through speaking with your GP, or directly to your local addiction service. You can see more information on OST here.  


If you are going through withdrawal, you might: 

  • Have nausea, constipation, diarrhoea stomach aches or changes in appetite 

  • Feel tired or lethargic 

  • Experience a headache or aches in your body or muscles 

  • Have difficulty sleeping 

  • Experience chills or cold sweats 

  • Have cravings to use more fentanyl or nitazenes  

  • Feel restless, agitated, anxious, depressed, or hopeless 

  • Have an increase in pain symptoms  

You can try: 

  • Following a tapering plan from a health professional to reduce your dose slowly  

  • Consider counselling, or support groups if feelings of anxiety and depression are getting worse 

  • Lean on a support network of friends, family, and professionals 

  • Stick to a routine - waking up, eating well, keeping active and rewarding yourself with things that bring you joy   

  • Practice mindfulness by writing down your feelings, doing breathing exercises or meditating 

If your symptoms worsen or don't go away, you have intense and lasting cravings to use more fentanyl or nitazenes, have vomiting or severe diarrhoea, have increasing pain symptoms, have insomnia, become constipated or have panic attacks, call a Doctor or Healthline (0800 611 116). 

If you are finding it difficult to stop using fentanyl or nitazenes alone, consider:  

  • Talking to your doctor about other medicines to help you get through withdrawal, including OST.  

  • Talking to your doctor about rehab or withdrawal clinics in your area – visit Health Point to see what services are available. 

  • Working with an addictions practitioner or counsellor to come up with a plan to cut down (‘tapering plan’) that will work for you.  

If you have persistent vomiting and/or diarrhoea, become dehydrated, have a fever, have severe pain, have chest pains or have significantly worsening mental health (such as suicidal thoughts or psychosis), these are signs that something serious might be going on. You or the people around you should act quickly and call 111.  

For more information on getting support for drug and alcohol use, see Finding support.  

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How can fentanyl/nitazene affect your daily activities?

Fentanyl and nitazenes are strong depressant drugs and slow down your brain and body functions. They can very quickly make you drowsy, disoriented, and uncoordinated. The effects or aftereffects of some types of fentanyl or nitazenes can last as long as 24 hours.  

As these drugs significantly affect your thinking, judgement and motor skills and can quickly cause you to become unconscious, it is very dangerous to drive or operate heavy machinery while using fentanyl or nitazenes. As the effects of these drugs can be very intense, trying to work, socialize or complete everyday tasks can be very difficult 

Will fentanyl/nitazene show up on a drug test? 

At some time in your life, an employer, a family member, or the NZ government, may ask you to take a drug test. It’s important to understand what drug tests can detect and what might happen if you fail one. 

Fentanyl and nitazenes may be tested for in several ways, such as blood, urine, or saliva. It is important to remember that people’s bodies are different and process drugs differently.  

Fentanyl may be tested for in routine tests, however nitazenes are harder to test for, and there is still limited information on how effectively they can be detected. Generally, fentanyl can be detected for 1-2 days in urine, 5-48 hours in blood and saliva and up to 90 days in hair. If you use fentanyl frequently, they may be more likely to show up for longer on these tests.  

If you are being prescribed fentanyl, it is a good idea to speak with your GP before you undergo a drug test.  

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Is fentanyl/nitazene illegal? 

Medicinal fentanyl (i.e patches) is regulated under the Medicines Act. Therefore it is legal to possess or use fentanyl if you have been prescribed it by a doctor. However, it is still illegal to sell or import medical fentanyl, even if you have a prescription.  

Fentanyl and nitazenes are illegal under the Misuse of Drugs Act. Fentanyl and some Nitazenes are Class B drugs. Analogues of fentanyl and nitazenes these drugs are considered Class C drugs. This means that using, buying, selling/supplying, possessing, or importing fentanyl and nitazenes is against the law.  

To find out more about the law around legal and controlled drugs, including cannabis see Drugs and the law. 

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