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Isotonitazene Facts

Opioid; Depressant; Mu-opioid receptor agonist

Description

Isotonitazene is a synthetic opioid of the benzimidazole class. It activates opioid receptors in the brain and spinal cord, powerfully suppressing pain and depressing breathing.

Subjective effects include pain suppression, euphoria, heavy sedation, pupil constriction, and respiratory depression. The entire profile is inferred — no voluntary human accounts exist, and every documented clinical presentation has ended in unconsciousness and respiratory failure.[1][2]

Isotonitazene produces severe physical dependence and is lethal at concentrations so small they require laboratory equipment to measure.[3] The drug clings to opioid receptors unusually long, so standard naloxone doses may fail to reverse an overdose; its main breakdown product is even more potent than the parent drug.[4][3][5]

Dose and durationby route · individual sensitivity varies

Insufflated(μg)
Threshold< 5 μgLight5 – 15 μgCommon15 – 40 μgStrong40 – 80 μgHeavy80+ μg

Starts in 1 – 5 minLasts 1 – 3 hoursAfter-effects 2 – 8 hours

Body and dependence

Acute toxicity
Critical
Chronic toxicity
Moderate
Physical dependence
High
Psychological dependence
High
Withdrawal
Severe · medical supervision
Compulsive redosing
High

Tolerance

Builds
Rapid
Fully resets after
14 days
Carries over to
morphine; fentanyl; heroin; oxycodone; hydromorphone; methadone; all MOR full agonists

Effectslikely at a common dose

Perception
none likely · 4 possible, including Visual acuity suppression, Spatial disorientation, Vestibular distortion
Body
Bodily heaviness; Muscle relaxation; Body high; Breathing alteration; Constipation; Motor control impairment; Pain suppression; Physical fatigue; Pupil constriction; Respiratory depression; Sedation; +14 possible, including Nausea, Dizziness, Excessive sweating
Thinking
Cognitive euphoria; Cognitive fatigue; Cognitive impairment; Focus suppression; +9 possible, including Analysis suppression, Compulsive redosing urge, Decision impairment
Feeling
Euphoria; +3 possible, including Dysphoria
Self
none likely · 5 possible, including Craving, Communication suppression, Social disconnection
Time
none likely · 2 possible, including Temporal disorientation

Who shouldn't take it

Absolute
Respiratory compromise; Concurrent benzodiazepine use; Concurrent opioid use; Concurrent alcohol use; Concurrent MAOI use
Relative
Hepatic impairment; Renal impairment

Combinations60 recorded

Lethal (4)
Benzodiazepines, Barbiturates; GHB, Baclofen; GHB, GBL; Local anesthetics
Dangerous (28)
Alpha-2 adrenergic receptor antagonist; Amphetamines; Anticholinergics; Antihistamines; Antipsychotics; Benzodiazepines; Buprenorphine, Kratom; Cannabis, THC; Clonidine, Guanfacine; Gabapentin, Pregabalin; MAOIs; MDMA, Amphetamines; MDMA, MDA; Naltrexone; NRIs; SNRIs; SSRIs; Stimulants; Synthetic cannabinoids; THC; Caffeine; CBD; Glutamate modulator; Huperzine A; and 4 more, see full page
Caution (19)
See full page: psychedex.org/substances/isotonitazene
Not graded (9)
Not listed never means safe.

Seek help immediately if

  • Unresponsive / can't be woken, even to a firm sternal rub
  • Slow, shallow, or stopped breathing
  • Pinpoint pupils
  • Blue/grey lips, fingertips, or skin (cyanosis)
  • Limp body; pale, clammy skin
  • Choking or gurgling sounds ("death rattle")
  • Slow, erratic, or absent pulse

What to do

  1. Try to wake them — shout their name, firm sternal rub
  2. Call emergency services immediately
  3. Administer naloxone if available
  4. Give rescue breaths (or CPR if there is no pulse)
  5. Place them in the recovery position
  6. Stay with them; re-dose naloxone every 2–3 minutes if there is no response
Reversal agent
Naloxone (Narcan) — opioid antagonist. May require repeated doses; its effect can wear off before the opioid does.

With prompt naloxone and rescue breathing, reversal is usually rapid. Because naloxone can wear off before the opioid — especially with long-acting opioids (methadone) or high-potency ones (fentanyl) — a period of monitoring is needed even after the person revives.

988 Suicide & Crisis LifelineFireside Project: 62-FIRESIDE

Version r1 · Not medical advice

References

  1. [1]
    ^Mueller F, Bogdal C, Pfeiffer B, Andrello L, Ceschi A, Thomas A, Grata E (2021) Isotonitazene: Fatal intoxication in three cases involving this unreported novel psychoactive substance in Switzerland. — Forensic Science International doi:10.1016/j.forsciint.2021.110686
  2. [2]
    ^Bendjilali-Sabiani JJ, Eiden C, Lestienne M, Cherki S, Gautre D, Van den Broek T, Mathieu O, Peyriere H (2024) Isotonitazene, a synthetic opioid from an emerging family: The nitazenes. — Therapie doi:10.1016/j.therap.2024.05.004
  3. [3]
    ^abDe Vrieze LM, Walton SE, Pottie E, Papsun D, Logan BK, Krotulski AJ, Stove CP, Vandeputte MM (2024) In vitro structure-activity relationships and forensic case series of emerging 2-benzylbenzimidazole 'nitazene' opioids. — Archives of Toxicology doi:10.1007/s00204-024-03774-7
  4. [4]
    ^Alhosan N, Cavallo D, Santiago M, Kelly E, Henderson G (2025) Slow dissociation kinetics of fentanyls and nitazenes correlates with reduced sensitivity to naloxone reversal at the mu-opioid receptor. — British Journal of Pharmacology doi:10.1111/bph.17376
  5. [5]
    ^Kozell LB, Eshleman AJ, Wolfrum KM, et al. (2024) Pharmacologic Characterization of Substituted Nitazenes at mu, kappa, and delta Opioid Receptors Suggests High Potential for Toxicity — Journal of Pharmacology and Experimental Therapeutics doi:10.1124/jpet.123.002052
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