Nitazenes

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KEY TAKEAWAYS

Nitazenes are new synthetic opioids 10x more potent than fentanyl and are used as recreational drugs in the UK, US, and other countries worldwide.

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What Is Nitazenes Addiction?

Protonitazene is a strong μ-opioid receptor agonist with 1.29x higher efficacy and a strong potential for addiction compared with fentanyl [1].

Consumption leads to decreased consciousness, particularly in overdose.

71.4% of varied substances are mixed with nitazenes, causing nitazene addiction to go unnoticed [2].

An individual who has consumed nitazenes appears euphoric and relaxed but, in severe cases, will not be able to communicate because of depressed levels of consciousness.

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Nitazenes Vs Other Opioids

Drug

Nitazenes

Heroin

Morphine

Strength

10x stronger than fentanyl [3]

1.5x stronger than morphine [4]

Administration

Vaping, sublingual, injection, nasal

Vaping, injection

Injection,

oral, rectal

Lasting drug effects

2 minutes-4 hours

2-4 hours

Short-acting morphine lasts for 2 to 4 hours

Reduces pain?

Comparable to morphine

Heroin acts quicker than morphine

Analgesic effects peak at 5-10 minutes 

Prescribed/illicit

Illicit

Illicit

Both

Drug

Codeine

Fentanyl

Strength

1/10 of the strength of morphine [6]

50 - 100 times more potent than morphine [7]

Administration

Oral, injection

Injection, transdermal, nasal, oral

Lasting drug effects

3-6 hours

72 hours

Reduces pain?

Analgesic effects peak at 2 hours

Analgesic effects peak at 2-5 minutes

Prescribed/illicit

Both

Both

Drug

Methadone

Tramadol

Strength

Equipotent to morphine

1/10 of the strength of morphine [5]

Administration

Smoking, nasal, injection, oral

Oral, nasal

Lasting drug effects

8 - 12 hours

Up to 24 hours in extended-release

Reduces pain?

Analgesic effects peak at 3 hours

Analgesic effects peak at 2 - 3 hours

Prescribed/illicit

Both

Both

Nitazenes Side Effects

Physical Side Effects

Nitazenes cause a depressed respiratory rate of 38±2% from baseline, leading to hypoxia and subsequent coma [8].

Consumption leads to coughing in 45% of cases, similar to strong fentanyl doses (7µg/kg) [9].

Lightheadedness and dizziness from morphine consumption occur at the same rate in nitazene-related consumption, even when the dose is smaller.

Consumption results in dizziness and confusion, and an individual will appear relaxed but zoned out.

Combined consumption with methadone, lualprazolam, and flubromazepam results in cardiac and respiratory arrest.

Psychological Side Effects

Nitazenes act on the opioid receptors within the central nervous system, leading to a relaxed mood and sedation.

Fentanyl users experience hallucinations, akin to nitazenes that also elicit psychoactive effects on opioid receptors.

Nitazenes presence in the bloodstream promotes GI protein signalling, reinforcing drug-seeking behaviours in users.

Overexpression of GI proteins reduces rewarding efficacy in the brain, resulting in tolerance.

High lipophilicity also results in rapid absorption, leading to euphoria faster than morphine.

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Mixing Nitazenes With Other Drugs


Heroin

Fentanyl

Why They Are Mixed With Nitazenes

Reduced heroin production means more demand for nitazenes


Nitazenes are cheaper


Nitazenes are sold online - more available 


45% of heroin users supplementing use with prescribed opiates now use nitazenes instead [10]


Reduces heroin withdrawal symptoms


Nitazenes and heroin act on μ opioid receptors

Drug sellers lace nitazenes in illegally bought fentanyl 


Nitazenes are  less restricted than fentanyl


Fentanyl’s analgesic effects increase with nitazenes 


Both nitazenes and fentanyl act on κ type opioid receptors

Physical Side Effects 

Reduced lung function and respiratory depression


>30% lowered body tissue oxygen  [11]


Hypoxia 


Inhibited pain


Apnea and lowered SpO2 (<88%) 


Increased opioid tolerance


Longer intoxication than heroin alone

Respiratory depression


Depressed levels of consciousness 


Increased self-reported pain


Increased opioid tolerance


Bradycardia

Psychological Side Effects

Depression and anxiety


Psychosis and paranoia 


Blunt emotions 


Confusion 


Drug-seeking behaviour 

Depression


Visual hallucinations


Cognitive and memory impairment 


Mental clouding and confusion


Drug-seeking behaviour


Oxycodone

Why They Are Mixed With Nitazenes

Drug sellers lace nitazenes in illegally bought oxycodone


Enhances euphoria and subjective high


Increased opioid dependency

 

Nitazenes are  less restricted than illicit use of oxycodone

Physical Side Effects 

Shallow breathing and respiratory depression


Serotonin syndrome 


Fever


Unresponsiveness and sedation

Psychological Side Effects

Euphoria 


Lowered episodic memory 


Reduced psychomotor functioning 


Drug-seeking behaviour 

What Settings Are Nitazenes Most Likely To Be Used In?

A history of mental health issues and substance misuse disorder are risk factors for combined consumption with oxycodone.

Individuals formerly prescribed narcotics for extreme pain relief seek illegal, stronger variations when a prescription is no longer available due to addiction. 

The global decrease in heroin production encourages drug sellers to substitute with new synthetic opioids to meet the demand of drug users.  

Drug sellers also cut nitazenes into heroin to generate more profit, as nitazene-related drugs are inexpensive in comparison. 

Stricter measures in place for prescribing opioids have seen a decrease in narcotics prescriptions, leading to a heightened need to source illicit nitazenes for users who are addicted.

The production of nitazenes is less regulated than non-synthetic opioids, making them more readily available.

Test strips cannot detect nitazenes in fentanyl, making it challenging for the user to know what substance is being consumed.

(Read about fentanyl rehabilitation here.)

Who Is More Likely To Take Nitazenes?

Profile Of Users Before Taking Nitazenes

Circumstances Leading To Nitazene Use

Oxycodone users

  • Illicitly bought oxycodone is cut with nitazene unknowingly to the user
  • Lack of education and drug testing leads individuals to take unknown substances

Fentanyl users (prescribed/non-prescribed)

  • Individuals with fentanyl prescriptions combine nitazenes that are 10x more potent
  • Fentanyl-tolerant individuals take nitazenes to continue feeling the same euphoric effects

Heroin users

  • 80% reduced production of heroin turns users towards more accessible nitazenes [12]

Poly-drug users

  • Individuals are 2.2x more prone to poly-drug use of nitazenes with peer influence [13]
  • Strict law enforcement on opioids turned users to nitazenes that are only just becoming controlled (2024)

At Risk Groups When Taking Nitazenes

Recently Detoxed

Tolerance decreases rapidly after detoxification of nitazenes, so if users administer the same high dose as before, this poses a hazard of side effects and overdose.

A lack of awareness of how much tolerance reduces in nitazene withdrawal leads to potentially fatal relapses, even if individuals take smaller doses of nitazenes than before.

Extended detox of nitazenes and other narcotics reduce respiratory tolerance, leading to respiratory depression and opioid-related overdose mortality during relapse.

Individuals who have been in prison for 2+ weeks have a 129x greater risk of severe opioid overdose upon release, and research demonstrates this rises when consuming of nitazenes [14].

Not Previously Taken Opioids

The volume of fentanyl required to cause 50% respiratory depression in opioid-naïve individuals is 333% less than in chronic opioid users, with this number rising in stronger opioid consumption [15].

Oxygen saturation can drop to SpO2 <88% within 4 hours of administration in opioid-naïve individuals beginning consumption [16].

Remifentanil-induced hyperalgesia rises by 180 ± 47% for opioid-naive patients with pre-existing pain, and this rises when stronger opioids are consumed [17].

Opioid-naïve individuals taking nitazenes experience immunosuppression and secondary infections compared to an individual who has been using the drug for longer.

Elderly

Opioid receptors are impaired in old age, making older people more susceptible to the factors commonly associated with beginner consumption. 

Chronic consumption generates histamine release, reducing blood pressure and vascular resistance in elderly users.

Elderly individuals are more at likely to develop opioid-induced urinary retention, where urinary retention occurs in 1 in 3 men over 80 years old [18] [19].

A 77% reduction in metabolism in the elderly leads to neurotoxicity of opioid consumption, as the drug accumulates in their body for longer [20] [21].

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Concurrent Prescribed Medication

There is a 1.23x greater risk of opioid overdose through the combined use of paroxetine or fluoxetine SSRIs and oxycodone, and research suggests this rises with more potent variations [22]. 

25% of reported cases of serotonin syndrome resulted from the combined consumption of SSRIs and opioid analgesics, and this rises with serotonergic nitazenes [23]. 

When combined with benzodiazepines, there is a 21.4x greater chance of emergency hospital admissions and opioid overdose [24].

Concurrent use of opioids with warfarin raises INR by 17.7%, leading to impaired blood clotting, especially when nitazenes are taken [25]. 

Mixing amphetamines with non-synthetic opioids enhances the analgesic effects.

(Read about amphetamine rehabilitation.)

Pregnancy

Narcotics use during pregnancy leads to a 6.4% rise in caesarian section births, and this increases when nitazenes are used [26].

3.1% of offspring from narcotics users required respiratory intervention for 7 days postpartum, with this increasing with potent strains [27].

Opioid use during pregnancy leads to neonatal syndrome, and this is 10x more likely when nitazenes are used throughout pregnancy due to their potency [28]. 

There is an elevated risk of stillbirth when the mother uses synthetic opioids during pregnancy, with this risk varying with the concentration of use.

Neonatal exposure to narcotics leads to a 68.4% heightened chance of developing chronic pain during childhood, with this risk being similar with nitazene consumption during pregnancy [29].

10% of pregnant women who inject their drugs develop HIV, and this is transmitted to their offspring in 1 in 20 cases [30]. 

Use Around The World


United States

United Kingdom

Prevalence

22% of illicit opioid cases [31]

36% of illicit drug cases [32]

Drug use/possession laws

Schedule I

Class A

Mortality rate

42 deaths in 2021 in Tennessee [33]

54 deaths in the last 6 months [34]

Cost of addiction treatment

Up to $20,000 (private)

Free (NHS)

Production/ trafficking route

From China

From China

Public Awareness

5 public announcements in 3 years

7 public announcements in 3 years

Demographics

Urban areas


Mostly males


White/black race


Low socioeconomic status


Homelessness

Urban areas


Homelessness


Low socioeconomic status


Nigeria

Brazil

Prevalence

83% of illicit drug cases [35]

95% of illicit opioid cases [36]

Drug use/possession laws

Monitored by United Nations

Class A1

Mortality rate

Data not available

Data not available

Cost of addiction treatment

£200 (private - GBP equivalent)

£1400 (GBP equivalent)

Production/ trafficking route

From China

From China

Public Awareness

1 public announcement in 3 years

1 public announcement in 3 years

Demographics

Urban/rural areas


21 - 30 year olds


Mostly males


Low socioeconomic status

Mostly females


Low socioeconomic status


Unemployment


Low family income

Legality

As of 22nd February 2023, 10 forms were made illegal in the UK:

  • Butonitazene
  • Etodesnitazene (etazene)
  • Flunitazene
  • Isotonitazene
  • Metodesnitazene (metazene)
  • Metonitazene
  • N-Desethylisotonitazene
  • N-Piperidinyl-etonitazene (etonitazepipne)
  • N-Pyrrolidino-etonitazene (etonitazepyne)
  • Protonitazene

Desnitroetonitazene and etonitazepyne are not officially controlled by the UK's Misuse of Drugs Act (1971), though these regulations are continually updated.

Individuals caught possessing, importing, or supplying any form of nitazene are subject to criminal charges under the Psychoactive Substances Act 2016. 

As soon as one variant becomes illegal, new strains appear in the illicit drug marketplace, taking up to 5 years to be made illegal. 

A lack of knowledge makes it challenging to identify this synthetic opioid, especially when mixed in other substances.

Nitazenes Recovery Challenges

The extent of withdrawal symptoms during immediate cessation is unknown, complicating detoxification care plans. 

64% of oxycodone users inadvertently take nitazenes that are laced in the drug [37].

A 50 times rise in narcotic potency increases the chance of relapse [38] [39].

Recovery From Overdose

10mg of naloxone for metonitazene overdose reverses cardiac arrest symptoms in 50% of cases, whereas up to 8mg reverses respiratory depression symptoms in 100% of N-piperidinyl etonitazene overdoses [40].

97% of overdoses require stronger and more frequent naloxone doses (1+) compared with fentanyl overdoses [41]. 

Intake of naloxone results in tachycardia, hypotension, or hypertension in 1-10% of individuals, and with large doses of naloxone required during nitazene overdose, these risks are increased.

Cerebral edema is seen in 22% of overdose cases, resulting in reduced brain functioning and ability to maintain detoxification programmes [42].

4.4mg of naloxone during opioid overdose increases the pulmonary complications risk by 62%, and this is further complicated in nitazenes overdose, where ~10mg is required [43].

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About the author

Philippa Scammell

Philippa Scammell MSci holds an integrated Master's degree in Psychology
from the University of York and has completed undergraduate statistical studies at Harvard University. Philippa has substantial experience in inpatient psychiatric care (Foss Park Hospital York), Research in Psychology at University of York, and group therapy facilitation (Kyra Women's Project). Philippa writes on clinical psychology and addiction recovery. Content reviewed by Laura Morris (Clinical Lead).

Last Updated: October 31, 2025