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U-47700 Facts

Opioid; Depressant; Benzamide; Mu-opioid receptor agonist

Description

U-47700 — Pink, U4 — is a synthetic opioid of the benzamide class. It activates opioid receptors in the brain and spinal cord, suppressing pain and slowing breathing.[1]

Subjective effects include euphoria, pain suppression, heavy sedation, and a warm dissolution of anxiety. The experience is a compressed opioid arc — an intense rush of warmth and pain dissolution that fades within hours, driving a compulsive compulsive redosing urge.

U-47700 produces rapid physical dependence, and fatal concentrations as low as 17 ng/mL[2] represent one of the narrowest effect-to-death margins in the opioid class. Most deaths involved combining it with benzodiazepines or fentanyl, stacking respiratory depression beyond what either produces alone.[3]

Dose and durationby route · individual sensitivity varies

Insufflated(mg)
Threshold< 1 mgLight4 – 6 mgCommon6 – 8 mgStrong8 – 10 mgHeavy10+ mg

Starts in 5 – 10 minLasts 2 – 3 hoursAfter-effects 2 – 4 hours

Body and dependence

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

Tolerance

Builds
Rapid
Fully resets after
1.5 weeks
Carries over to
morphine; heroin; fentanyl; oxycodone; methadone; buprenorphine; all opioids

Effectslikely at a common dose

Perception
none likely · 1 possible
Body
Pain suppression; Pupil constriction; Sedation; Bodily heaviness; Body high; Tactile euphoria; Muscle relaxation; Constipation; Breathing alteration; +12 possible, including Nausea, Dizziness, Motor control impairment
Thinking
Cognitive impairment; Cognitive fatigue; +13 possible, including Analysis suppression, Information processing suppression, Decision impairment
Feeling
Euphoria; Anxiety suppression; +1 possible
Self
Craving; +4 possible, including Communication suppression, Social disconnection
Time
none likely · 2 possible, including Temporal disorientation

Who shouldn't take it

Absolute
Respiratory compromise (COPD, asthma, sleep apnea); Pregnancy; Concurrent CNS depressant use; Opioid-naive status at above-threshold doses
Relative
Significant hepatic impairment; CYP3A4 inhibitor co-administration

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/u-47700
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]
    ^Baumann MH, Majumdar S, Le Rouzic V, et al. (2018) Pharmacological characterization of novel synthetic opioids (NSO) found in the recreational drug marketplace — Neuropharmacology doi:10.1016/j.neuropharm.2017.08.016
  2. [2]
    ^Mohr AL, Friscia M, Papsun D, Kacinko SL, Buzby D, Logan BK (2016) Analysis of Novel Synthetic Opioids U-47700, U-50488 and Furanyl Fentanyl by LC-MS/MS in Postmortem Casework — Journal of Analytical Toxicology PMID:27590036
  3. [3]
    ^Fels H, Lottner-Nau S, Sax T, Roider G, Graw M, Auwaerter V, Musshoff F (2019) Postmortem concentrations of the synthetic opioid U-47700 in 26 fatalities associated with the drug — Forensic Science International doi:10.1016/j.forsciint.2019.04.010
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