Fentanyl and its analogues are very potent opioids and have been linked to more than 100,000 deaths in recent years in North America. We do not currently have fentanyl mixed in the drug supply in New Zealand, but some people do use it. Fentanyl and its analogues should be used with extreme caution as they are very easy to overdose on.

Key things to know

Consider carrying the overdose reversal drug naloxone with you. If someone is overdosing from opioids, it can save their life

Naloxone info

Start with a lower amount and wait an hour before deciding to take more

Safer using

If injecting, visit your local needle exchange for new needles and info on safer injecting

Safer injecting

Try to be with a sober person that knows the signs of an opioid overdose and can get help if needed

Avoiding overdoses

Use drug checking services to make sure it isn't mixed with something else

Drug checking info

How do prescription opioids make you feel?

Prescription opioids are a large group of drugs. How long the effects from these drugs last can depend on which drug you use, whether they are immediate-release or extended-release, and how you take them. Prescription opioids all have different strengths and doses and can affect everyone differently depending on their individual body. 

Remember a low dose for one person can be a high dose for another, as people’s bodies process drugs differently.

We spoke to a female in her 20's that uses Tramadol regularly:

“When I was first prescribed it made me feel relaxed, warm and fuzzy, but it can also make you feel a little sick. I sometimes would have trouble keeping my thoughts straight”.

Pleasant Effects 

Unpleasant Effects 

Physical relaxation


Relaxed and calm 

Reduced anxiety or stress

Reduced feelings of physical pain

Feeling ‘warm’ or ‘safe’

Pleasant feeling of sleepiness

Feelings of invincibility




Tired or lethargic

Itchiness (on face and body)

Lack of appetite

Mood swings


Muscle weakness


Impaired Judgement

Clumsy or having a lack of coordination

Pleasant Effects 

Unpleasant Effects 

Increased relaxation

Increased euphoria

Physical sensations of ‘floating’

Lack of pain

Feeling physically numb 

Feeling emotionally numb

Increased drowsiness

Feeling very nauseous 


Excessive sweating

Changes in heartrate

Sore stomach

Slowed breathing


Increased mood swings

Mild hallucinations

Erectile dysfunction

Pleasant Effects 

Unpleasant Effects 


Severe vomiting

Severe abdominal pain

Extremely confused or disoriented 

Blue lips and cold, clammy skin

Becoming unresponsive (unable to wake up)

Losing consciousness

Severe changes in heartrate


Difficulty breathing or very shallow breathing


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How much opioids do people usually take?

There are no publicly available tests to measure how strong your drugs are, so often people start low and go slow.

This information is not a recommended dosage amount. It can't take account of your specific circumstances. Drugs affect everybody differently, depending on things like your body size, any other drugs you’ve taken, what you have eaten, where you are, and how you're feeling. Find out more under the safer using section. 

Remember, drug checking can tell you what is in your drugs, but can’t tell you how strong they are.  

The information below is from other websites about how much people commonly use overseas. It is not a recommendation and typical usage in Aotearoa may be different.

How much codeine do people usually take - swallowed (from

Light 50 - 100mg
Common 100 - 150mg
Strong 150 - 200mg
Heavy 200mg+

How much morphine do people usually take - swallowed (from

Light 5 - 10mg
Common 15 - 20mg
Strong 30mg+

How much methadone do people usually take - swallowed (from

Light 5 - 10mg
Common 10- 20mg
Strong 20 - 35mg

How much oxycodone do people usually take - swallowed (from

Light 2.5 - 10mg
Common 10 - 25mg
Strong 25 - 40mg

How much oxycodone do people usually take - snorted (from

Light 2.5 - 7.5mg
Common 7.5 - 15mg
Strong 15 - 25mg

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How can you be safer when using prescription opioids? 

Note: Prescription opioids are commonly prescribed drugs. If your doctor has prescribed these to you, it is best to get their advice about how to take them and what to do if you experience unexpected or unpleasant effects.

Prescription opioids are a large group of drugs and there are different things you can do to be safer for each one. However, there are some general things you can do to reduce the risk when using any prescription opioid.

Consider carrying the opioid overdose reversal drug naloxone. If you are using opioid drugs often, you or the people around you may want to consider accessing the life-saving drug naloxone. In New Zealand, naloxone comes in the form of a nasal spray called Nyxoid, or in an injectable form. 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 either of these by a doctor or you can buy Nyxoid as part of an emergency kit at some pharmacies. Some needle exchanges and opioid substitution treatment centres may be able to help you get naloxone.

We've got info on how to use Nyxoid nasal spray, and how to use injectable naloxone.

Test your prescription opioids, especially if they are bought illegally. Some people choose to take prescription opioids that are not prescribed to them. If you’re planning on taking prescription opioids that you have purchased illegally, or been given, it’s important not to assume you know what is in them. There are counterfeit prescription opioids that may contain other psychoactive ingredients or fillers that can be dangerous. You can take your prescription opioids to a drug checking clinic that uses an FTIR spectrometer. 

If you aren’t sure whether you have fentanyl, you can use a fentanyl test strip at home, or at a drug checking clinic.

Caution: Fentanyl test strips will not pick up on all fentanyl analogues. A negative test does not always mean you do not have fentanyl.

Learn about the specific opioid you plan to take. Even if you know what you have, different prescription opioids have different effects. These drugs are dosed differently too, so the same amount of two different opioids can cause very different effects. Counterfeit prescription opioids or ones imported from overseas may also have different doses to those available in New Zealand. You can search for specific dosage and strength information on tripsit.

Start with a lower dose and wait an hour before re-dosing. Prescription opioids can have different effects on everyone. People develop tolerance if they use them often, so if you are new to using, avoid basing your dose off what the people around you take. Consider starting with a low dose and waiting at least an hour to feel the effects before redosing. If you are using prescription opioids orally, remember that it will take longer to feel the effects- so it is extra important to wait. 

Take care if you are snorting or injecting prescription opioids. Snorting or injecting prescription opioids delivers them faster to you blood stream, so the effects come on quicker but are shorter-lasting. Consider taking a smaller dose if you are snorting or injecting, as these methods carry a higher risk of overdosing. Snorting any drug can cause damage to your nasal passage. This is especially the case for prescription pills as they have lots of binders and fillers in them that can be harmful to snort. Try taking long breaks between snorting to decrease the risk of damaging your nose. You can also reduce the damage to your nose by doing a nasal saline wash after snorting. For a guide on how to do this, see our 'How to do a sinus flush' article. Use a clean snorting surface and tool (like a paper straw) every time and do not share with others. If you are injecting, make sure to use clean equipment (including needles) every time and do not share with others. You can access clean injecting equipment from your local needle exchange. It is recommended that you avoid injecting in the same place every time as this can cause more damage and infection to the area.

For more information on how to be safer if injecting or snorting, see our drug safety section.

Have a sober buddy and make sure they know the signs of an opioid overdose. Opioid overdoses can happen quickly and can be deadly if someone doesn’t get medical help. It is a good idea to have a sober buddy around who can get help if something goes wrong. If someone is overdosing you should call 111 or get medical help immediately. The signs of an opioid overdose include:

  • Unconsciousness and the person doesn’t respond to their name or being touched
  • Difficulty breathing
  • Making choking, gurgling or snoring sounds
  • Blue lips, tongue and hands and their skin is cool and pale
  • Pinpoint pupils

For more information about opioid overdose, see the If you've had too much section.

For more information on how to be safer when using drugs and alcohol, see Safer using.  

To order self-help workbooks and other free resources for safer use, see Resources

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What happens if you have too many opioids?

The unpleasant effects of prescription opioids can range from feeling mildly unwell to experiencing a potentially life-threatening overdose. There is no specific amount of a drug that will cause an overdose, this depends on what drug you are using, how often you use and your individual body.

For more information on what you can do to decrease you risk of overdosing, see Safer using.

You might feel nauseous, dizzy, tired, sweaty or lethargic. You might get confused or disoriented and have impaired judgement. You could feel moody or irritable, have muscle weakness or loss of appetite, or experience erectile dysfunction.


  • Focus on breathing try taking slow and deep breaths.  
  • If you are able, call and talk to somebody you trust and ask them to help keep you calm.  
  • Do not take more opioids, alcohol, or other drugs, as these can make you feel worse.  
  • Move to somewhere quiet try to sit, lay down and do something relaxing.  
  • Drink water to stay hydrated.  

If you're vomiting or have a sore stomach, feeling extremely drowsy, experiencing severe changes in temperature, have dizziness or difficulty walking, have hallucinations, have changes in heartrate or slowed breathing, call a doctor or Healthline (0800 611 116). You won't get in trouble if you tell them you've used drugs. 

If you're extremely hot or cold, have tiny 'pinpoint' pupils, are unresponsive, unable to stay awake, have hallicinations or delusional thoughts, have slowed, shallow breathing or having difficulty breathing, lose consciousness or have seizures, these are signs of an overdose. You or the people around you should act quickly. Call 111 and administer naloxone if you have it.

If you experience unexpected or concerning effects from prescription opioids you can notify High Alert to help keep others safe.


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What do opioid comedowns feel like, and how can you feel better?

If you are using prescription opioids, you are unlikely to experience a 'comedown' in the same way you do from stimulants like MDMA or cocaine. However you may experience aftereffects as these drugs wear off. If you use opioids regularly, you might find you experience withdrawal symptoms as the effects wear off. Also, if you are using these drugs for the treatment of physical pain, you might also find that the pain returns. 

The comedown time for these drugs can vary depending on which opioid you have taken, how much you have taken, how you have taken it and how often you use. Most people who use prescription opioids occasionally don’t experience many comedown symptoms, while people who use daily, or large amounts are more likely to experience unpleasant comedowns.

If you're coming down from prescription opioids, you may:

  • Experience a return of your usual physical pain, or get new muscle pain
  • Have a runny nose
  • Feel nauseous
  • Have mild changes in bowel habits, like diarrhea or constipation
  • Feel anxious
  • Experience low mood
  • Feel irritable or restless
  • Have difficulty falling asleep or staying asleep

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

If any of these symptoms intensify or don't go away then call a doctor or Healthline 0800 611 116. They can talk you through the next steps.

If  your symptoms worsen or you are with somebody who: 

  • Has severe tremors
  • Experiences extreme body pain
  • Experiences suicidal thoughts
  • Has severe or continual vomiting
  • Becomes severely dehydrated
  • Experiences psychosis
  • Has seizures
  • Loses consciousness

Call 111. These are signs that something more serious is going on. You or the people around you should act quickly.

A reddit user that uses oxycodone talks about a comedown that they experienced:

“me and my friend took half an 80mg Oxycodone (Sandoz). About 4 hours into the experience, I was feeling horrible, it felt like an MDMA comedown”

Another Reddit user discusses a different comedown experience from the same drug:

“Normally if I take a really high dose, after I’m just tired a little moody sometimes a little anxious but nothing like a stim comedown”

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What are the long-term effects of opioids? 

If you are being prescribed an opioid drug and taking it as recommended, speak with your doctor if you are concerned about the effects from long-term medical use of these drugs.

Long-term use of prescription opioids can have effects on your brain and your body. Some of the physical effects of long-term use include a weakened immune system, gastro issues (like constipation), breathing problems (especially when sleeping), heart problems, increased sensitivity to pain, sexual dysfunction and dental issues. The long-term impact of prescription opioid use depends on many things, such as: how long you use them for, how much you take, which drug you use and your individual body.

Long-term use of prescription opioids can also have effects on your brain and mental health. Research has shown that long-term use can increase the risk of developing anxiety, depression and making existing depression worse. Some research shows that long-term opioid use can cause problems with memory. It is important to keep in mind that people with existing mental health issues have an increased likelihood of long-term opioid use, which can make it difficult to understand the relationship between opioid use and mental health.

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How do you manage withdrawal from opioids? 

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

How unpleasant your withdrawal symptoms are depends on how long you have used for, how much you use, and which type of prescription opioid you use. If you are using these drugs (legally or illegally) to treat pain or other physical disorders, you may find that your symptoms come back quickly. People who have used prescription opioids every day for a long period, may find that stopping suddenly (going ‘cold turkey’) can be too difficult and may need to taper their dose down slowly by getting support from a doctor or accessing opioid substitution treatment (OST).

You might:

  • Experience return of physical pain you usually have
  • Have a runny nose
  • Feel nauseous, have diarrhoea or less commonly, constipation
  • Feel anxious or low, or feel a general sense of dissatisfaction with life
  • Feel irritable or restless
  • Have difficulty falling asleep or staying asleep

You can try:

  • Consider counselling, or support groups if feelings of anxiety and depression are getting worse 
  • Lean on a support network of friends, whānau, 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 you experience pain that is worse than is usual for you, have headaches, vomiting or extreme diarrhea or constipation, have chills or sweating, experience tremors or shakes or have a racing heart, call a doctor or Healthline (0800 611 116).

Severe tremors, extreme pain, acting violently, severe or continual vomiting, becoming severely dehydrated, having suicidal thoughts or attempting suicide, psychosis, having seizures or losing consciousness are signs that something more serious is going on. You or the people around you should act quickly. Call 111. 

A Reddit user talks about their withdrawal symptoms after stopping regular codeine use:

“The symptoms [shivering, bowel issues, anxiety] will intensify until about the end of the third day when they'll begin to recede and then burn out around the 7th-8th day. You'll feel a bit raw and have a low mood for a few weeks after the withdrawal is over”

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

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How can opioids affect your daily activities?

Prescription opioids, even when taken as prescribed by a doctor can cause impairment that can affect your work or daily activities. The effects of prescription opioids can vary in how long they last depending on which prescription opioid you use, how you use it and whether it is extended-release or immediate-release.

Prescription opioids can make you feel dizzy, confused, nauseous and can impair your judgement. These drugs can also make you feel like you are thinking slowly, which can make interacting with others difficult. One of the main issues with prescription opioids is that these drugs cause drowsiness. For some people this can make it hard to stay awake or do normal daily tasks. Due to these effects, it is important to avoid driving or operating heavy machinery when you are using prescription opioids.

Research suggests that impairment from prescription opioids is more likely to occur in people who are new to using them. Impairment is also more common in people using opioids recreationally. If you are taking prescription opioids that are prescribed to you by a doctor, you can check with them if you are worried about experiencing impairment at work or in your daily life.

If you take prescription opioids, will it show up on a drug test?

Opioids are commonly tested for. As there are so many prescription opioids, the detection times can vary depending on which drug you use, how much you use and your individual body. Based on research, it appears that prescription opioids can be detected for less than 48 hours in blood , 1-3 days in urine, 1-4 days in saliva  and up to 90 days in hair. 

False-positive tests for opioids can occur from the use of medicines such as dextromethorphan, diphenhydramine, quinine, quinolones, rifampin and verapamil. False-positives for opioids can also occur from eating poppy seeds. One study showed that as little as 25g of poppy seeds could cause a false-positive on some opioid drug tests. If you are expecting a drug test it may be a good idea to avoid eating poppy seeds beforehand. As heroin is difficult to detect in many types of drug tests, this may also show up as codeine or morphine on a drug test instead. If you are taking a medicine that you are concerned may cause a false-positive, you should speak with your doctor before taking a drug test.

If you are taking prescription opioids as prescribed and are expecting a drug test, you can speak with your doctor and the organization requesting the test to discuss the next steps. It is a good idea to do this before you take a drug test.

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Are prescription opioids legal?

Many prescription opioids are available in New Zealand, and they are considered controlled drugs under the Medicines Act. This means that it is illegal to use these drugs if they are not prescribed to you. You also cannot sell/supply, import, or manufacture these drugs, even if you have a prescription for them.

Some prescription opioids carry additional penalties under the Misuse of Drugs Act. Morphine, oxycodone, methadone, fentanyl, and some fentanyl analogues are all Class B Controlled Drugs. Other fentanyl analogues and buprenorphine are Class C Controlled Drugs under the misuse of drugs act. This means that it is illegal to use or possess these drugs without a prescription and illegal to buy, sell/supply, make or import these drugs.

You are allowed to carry and use these medicines if they are prescribed to you by a doctor and are using them as they are prescribed. If you have been prescribed these medicines overseas, you can usually bring in a 3-month supply of them, if you declare and prove they are prescribed to you. You can see more information on this on Medsafe’s website.

You can also get in trouble with the law if you are found to be ‘impaired’ while driving, and a blood test finds evidence of prescription opioids in your system.

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

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