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Acetylfentanyl Facts

Opioid; Depressant; Anilidopiperidine; Mu-opioid receptor agonist

Description

Acetylfentanyl is a synthetic opioid of the anilidopiperidine class. It activates opioid receptors in the brain, suppressing pain signaling and slowing breathing.

Subjective effects include profound pain suppression, euphoria, heavy sedation, anxiolysis, and a warmth that narrows consciousness. The experience mirrors fentanyl — pain and distress dissolve rapidly into a heavy, quiet calm — but compressed into a shorter window.

Acetylfentanyl produces rapid physical dependence, and the gap between an active dose and a fatal dose is critically narrow[1][2] — 23 times narrower than fentanyl's and 10 times narrower than morphine's. Tolerance to euphoria builds faster than to respiratory suppression, so dose escalation tightens the margin toward fatal overdose.

Dose and durationby route · individual sensitivity varies

Sublingual(mg)
Threshold< 2 mgLight5 – 10 mgCommon10 – 15 mgStrong15 – 20 mgHeavynot recorded

Starts in 20 – 40 minLasts 1 – 4 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
10.5 days
Carries over to
fentanyl; morphine; heroin; oxycodone; hydromorphone; methadone; all mu-opioid receptor agonists

Effectslikely at a common dose

Perception
none likely · 4 possible, including Visual acuity suppression, Visual haze / noise
Body
Bodily heaviness; Body high; Breathing alteration; Constipation; Muscle relaxation; Pain suppression; Pupil constriction; Sedation; Tactile euphoria; +17 possible, including Motor control impairment, Nausea, Respiratory depression
Thinking
Cognitive euphoria; +19 possible, including Cognitive impairment, Compulsive redosing urge, Decision impairment
Feeling
Anxiety suppression; Euphoria; +2 possible, including Empathy suppression
Self
Craving; +6 possible, including Communication suppression, Social disconnection
Time
none likely · 2 possible, including Temporal disorientation

Who shouldn't take it

Absolute
Respiratory insufficiency or compromised airway; Concurrent CNS depressant use; Opioid-naïve individuals receiving tolerant-calibrated doses
Relative
Head injury or raised intracranial pressure; Hepatic impairment; Pregnancy

Combinations62 recorded

Lethal (6)
Benzodiazepines, Barbiturates; GHB, Baclofen; GHB, GBL; Ketamine; Local anesthetics; Tramadol
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/acetylfentanyl
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]
    ^Takase I, Koizumi T, Fujimoto I, Yanai A, Fujimiya T (2016) An autopsy case of acetyl fentanyl intoxication caused by insufflation of 'designer drugs'. — Legal medicine (Tokyo, Japan) doi:10.1016/j.legalmed.2016.05.006
  2. [2]
    ^Schueler HE (2017) Emerging Synthetic Fentanyl Analogs. — Academic forensic pathology doi:10.23907/2017.004
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