What are fentanyl and nitazenes? Explaining the rise and risks of potent synthetic opioids

Reports that people are accidentally taking potent synthetic opioids are increasing worldwide. And so are the harms caused by them.

Here we explore what they are, why they can be dangerous, and ways to reduce the risks.

What are potent synthetic opioids?

Potent synthetic opioids are a lot stronger than other opioids, meaning people can overdose on even a small amount.¹

Opioids include any natural or synthetic drugs that come from, or are related to, the opium poppy plant – these drugs act on the opioid receptors in the brain.

A ‘natural’ opioid like morphine is made from the plant. A synthetic opioid like fentanyl is made in a lab. There are also semi-synthetic opioids like heroin, which are drugs where the plant has been altered in a lab.

More commonly known potent synthetic opioids include:

• nitazenes
• fentanyl
• fentanyl analogues like carfentanil or acetyl fentanyl.

Use around the world

In the United States, the rate of overdose deaths related to potent synthetic opioids have increased by more than 20 times in less than a decade. In 2022, potent synthetic opioids were involved in 68% of all overdose deaths.^2,3

In England, deaths involving nitazenes are of increasing concern. In the first year of the UK monitoring nitazene deaths, 179 deaths were reported between June 2023 and May 2024.¹

In Australia, nitazenes were first detected in 2021 and have since been found in every state/territory, except for Tasmania.⁴ They are increasingly involved in preventable overdose deaths.⁴

While Australia isn’t experiencing the same level of impact that Europe and the Americas are, the increased presence is concerning.

Where do potent synthetic opioids come from?

In the early 1900s, scientists created and studied over 300 synthetic opioids, hoping to discover an opioid that did not cause people to develop dependence or tolerance.⁵

Through the 1950s and 1960s, scientists invented a number of potent synthetic opioids, including fentanyl, fentanyl analogues and nitazenes.^5,6

Since they were invented, fentanyl and fentanyl analogues have always been found in illegal drug markets. But, in the last 10 years, their presence in global illegal drug markets has increased.⁷

Nitazenes weren’t common until they were detected in Europe in 2019.⁶ Since then, they’ve also been found in Asia, North America, South America and Oceania.⁸

Fentanyl and fentanyl analogues

Fentanyl is up to 100 times stronger than morphine.⁹

Doctors have used fentanyl as a medicine for over 50 years. Patients can take it by nose, mouth, injection and through the skin. Patients with chronic severe pain can use fentanyl if they are tolerant to other opioids.⁵

Fentanyl analogues are very similar to fentanyl but have small changes to their chemical structure, meaning they vary in effects and strength.¹⁰

Nitazenes

Nitazenes , also called benzimidazole-opioids, are a group of synthetic opioids that vary in strength. Some nitazenes are similar in strength to morphine, others can be a lot stronger than fentanyl.⁶

Because of their high risk for overdose, nitazenes were never used in medicine.⁶

Why are potent synthetic opioids becoming more common?

Potent synthetic opioids have been around for over 60 years – so why are they on the rise now?

There are many possible reasons why potent synthetic opioids are appearing more in illegal drug markets:

• Compared to heroin, potent synthetic opioids are low-cost and easier to make and transport. They’re stronger so less is needed to get the same effect.¹¹
• Afghanistan’s ban on opium production has led to global production decreasing by 74% in 2023.¹² Afghanistan was one of the world’s largest opium growers and exporters. This appears to have also led to an increased availability of other synthetic opioids.^13,14
• They can be sold on the dark web (online markets for illegal goods), which has increased accessibility and makes it harder for border patrol and police to find.¹⁵
• Creating new drugs that have small chemical differences to existing drugs in the market also makes it harder for border patrol and police to find them.¹⁵

These factors are also likely leading to a rise in other synthetic drugs like novel benzodiazepines and synthetic cathinones.¹⁵

What are the risks of potent synthetic opioids?

Potent synthetic opioids vary significantly in strength and effects, meaning they come with a high risk of overdose or other drug-related emergencies.

Drugs like cocaine and MDMA are increasingly being contaminated with potent synthetic opioids. This can result in people accidentally using them without knowing, thinking they are taking something different.

This has occurred in Australia and overseas, leading to overdose deaths that could have been prevented.¹⁶

Potent synthetic opioids can be:

• used as a cheap ingredient to make other illegal opioids like heroin stronger
• mixed with in other drugs, such as benzodiazepines, cocaine or MDMA
• sold as counterfeit medicines (such as Oxycodone®), because it’s a cheap alternative.^4,9

They can also cause dependence and have dangerous interactions with other drugs (especially depressants like benzos or alcohol).

So – what can we do to reduce the risks of potent synthetic opioids?

Reducing harms from potent synthetic opioids

If you or someone you care about is using drugs, there are some evidence-based strategies for reducing harms from potent synthetic opioids, these include:

Naloxone

Naloxone (also known as Nyxoid®/Narcan®) temporarily reverses the effects of opioid overdose.¹⁷ For potent synthetic opioids, more than one dose may be needed. Don’t give more naloxone if the person is responding - this can cause very unpleasant withdrawal symptoms.¹⁸

It’s available for free over the counter from your local pharmacy and can be used by anyone, including family or friends and bystanders.¹⁷ Speak with your chemist or pharmacist for more information and encourage family and friends to learn how to use and to carry naloxone.

Pill testing and drug alerts

Pill testing (drug checking) allows a person to test their drugs and to speak to trusted health professionals and peer workers about drug use.¹⁹ By testing their drugs, people learn what it actually contains and how strong it is. This can lead to a person not taking it, potentially saving their life.^19,20

Findings from drug checking services can also be used to alert the public. For example, when CanTEST identify potent synthetic opioids in a sample they’re testing, they release a drug alert to warn the public.

Drug checking and drug alerts change behaviours, with people:

• stopping using the drug entirely
• avoiding using drugs matching the alert
• changing their approach to using the drug – most commonly by using a smaller amount, or ‘starting low, going slow’.^21-23

Other strategies for reducing harm

• ‘Start low, go slow’, pace yourself by only taking a little of the drug to start with, and leave time between doses.
• Never use alone, make sure someone nearby has naloxone on hand and a phone to call for help if needed.
• Avoid mixing drugs (see polydrug use), especially mixing with other opioids or depressants because this increases the risk of overdose.

More info

• What are nitazenes and why are they being found in heroin and ketamine in Australia?
• Emerging drug briefing: nitazenes
• Opioids more potent than fentanyl are in Australia. So what are nitazenes?
• Victoria needs a potent synthetic opioids plan

This article has been reviewed by the National Centre for Clinical Research on Emerging Drugs (NCCRED).