Skip to main content
Psychedex
Facts label

F-Phenibut Facts

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

Dose and durationby route · individual sensitivity varies

Oral(mg)
Threshold< 50 mgLight100 – 150 mgCommon150 – 400 mgStrong400 – 600 mgHeavy600+ mg

Starts in 20 – 60 minLasts 6 – 8 hoursAfter-effects 2 – 6 hours

Body and dependence

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

Tolerance

Builds
Rapid
Fully resets after
10.5 days
Carries over to
phenibut; baclofen; GHB; GBL; alcohol; benzodiazepines

Effectslikely at a common dose

Perception
none likely · 2 possible
Body
Muscle relaxation; Sedation; +16 possible, including Motor control impairment, Dizziness, Nausea
Thinking
none likely · 20 possible, including Cognitive impairment, Compulsive redosing urge, Analysis suppression
Feeling
Anxiety suppression; +8 possible, including Anxiety, Depression, Dysphoria
Self
none likely · 10 possible, including Craving, Ego inflation
Time
none likely · 1 possible
Awareness
none likely · 1 possible

Who shouldn't take it

Absolute
Respiratory insufficiency; Pregnancy; Concurrent CNS depressant use
Relative
Epilepsy; Substance use disorders; Renal 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/f-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/f-phenibut · Version r1 · Not medical adviceValues as of
On the printout