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Psychedex
Facts label

Phenibut Facts

Depressant; Anxiolytic; Substituted phenethylamine; GABA-B receptor agonist

Dose and durationby route · individual sensitivity varies

Oral(mg)
Threshold< 250 mgLight500 – 1000 mgCommon1000 – 2000 mgStrong2000 – 3500 mgHeavy3500+ mg

Starts in 1.5 – 3 hoursLasts 10 – 16 hoursAfter-effects 6 – 24 hours

Body and dependence

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

Tolerance

Builds
Rapid
Fully resets after
Not recorded
Carries over to
baclofen; gabapentin; pregabalin; benzodiazepines

Effectslikely at a common dose

Perception
none likely · 3 possible
Body
Sedation; +14 possible, including Motor control impairment, Dizziness, Insomnia
Thinking
none likely · 13 possible, including Compulsive redosing urge, Cognitive impairment, Analysis suppression
Feeling
Anxiety suppression; +8 possible, including Anxiety, Dysphoria, Depression
Self
none likely · 5 possible, including Craving

Who shouldn't take it

Absolute
Respiratory disease; Pregnancy; Concurrent CNS depressant use
Relative
Substance use disorder; Anxiety disorders; Hepatic impairment

Combinations60 recorded

Lethal (2)
GHB, GBL; Opioids
Dangerous (36)
Alpha-2 adrenergic receptor antagonist; Antihistamines; Antipsychotics; Benzodiazepines; Benzodiazepines, Barbiturates; Buprenorphine, Kratom; Cannabis, THC; Clonidine, Guanfacine; MDMA, Amphetamines; Synthetic cannabinoids; Amphetamines; Anticholinergics; Atypical antipsychotics; Buspirone; Caffeine; Cannabis; Dopamine agonists; DXM; GHB, Baclofen; Ibogaine; Ketamine, DXM, PCP; Lithium; Local anesthetics; MAOIs; and 12 more, see full page
Caution (13)
See full page: psychedex.org/substances/phenibut
Not graded (9)
Not listed never means safe.

Seek help immediately if

  • Extreme drowsiness — can't stay awake or be roused
  • Confusion, slurred speech, severe loss of coordination
  • Slow, shallow, or irregular breathing
  • Unconsciousness / unresponsive; limp, floppy body
  • Blue lips or fingertips
  • Vomiting while sedated (choking / aspiration risk)
  • Cold, clammy skin; weak pulse

What to do

  1. Try to wake them — shout, firm sternal rub
  2. If unresponsive or breathing is impaired, call emergency services
  3. Place them in the recovery position — critical, they can choke on vomit
  4. Monitor breathing continuously; be ready to give rescue breaths / CPR
  5. Never leave them alone to "sleep it off"
  6. Do not give other drugs, stimulants, or more depressants

Most depressant overdoses resolve with airway protection, breathing support, and monitoring. The danger is respiratory depression and choking on vomit — sharply worse when combined with opioids or alcohol. GHB/GBL overdoses often involve sudden deep unconsciousness and may self-resolve, but airway protection is essential.

988 Suicide & Crisis LifelineFireside Project: 62-FIRESIDE

psychedex.org/substances/phenibut · Version r1 · Not medical adviceValues as of
On the printout