Phenibut for Health & Longevity - Quick Reference Sheet
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Phenibut for Health & Longevity

Created on 10/08/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 5.5 – Audit

Phenibut, a synthetic relative of the brain's main calming messenger, is a prescription medication in Russia for anxiety and poor sleep and is sold elsewhere online for calm and focus. Studies report less anxiety and better sleep, but none used a placebo, so these benefits are unconfirmed. Dependence and withdrawal, including seizures, are well documented, mostly with large daily amounts. Nothing links it to slower aging or longer life. (Full Review)

Protocol

Standard clinical dose
250–500 mg three times daily
250 mg in Latvian general practice; 500 mg in Russian anxiety trials; split dosing is standard
Daily range and ceiling
0.25–2 g/day
Sources differ: 2.5 g/day maximum on Russian fact sheets
Course length
3–6 weeks
Anxiety benefits faded within a month after a 21-day course but persisted after a 60-day course
Time to effect
Anxiety and stress-related symptoms
3 weeks
Stress-symptom score fell after 3 weeks of 250 mg three times daily (no control group)
Dizziness and headache
60 days
Reduced more than with an anti-vertigo drug over 60 days in one controlled trial
Subjective sleep quality
21 days
Sleep score improved after 21 days in post-COVID patients (no control group)

Benefits

Contraindications
  • Pregnant women
  • Breastfeeding women (theoretical; no lactation data exist)
  • Children and adolescents
  • People with current or past alcohol or drug use disorder
  • People who regularly use alcohol, opioids, benzodiazepines or other sedatives
  • People with significant kidney impairment (theoretical; no source gives a threshold)
    •
Key Interactions
  • Alcohol: Avoid
  • Benzodiazepines (alprazolam, diazepam, clonazepam): Avoid
  • Opioids (oxycodone, methadone, tramadol): Avoid
  • Gabapentinoids (gabapentin, pregabalin): Avoid (theoretical)
  • Baclofen: Avoid (theoretical) for unsupervised combined use
  • Cannabis and THC-containing products, including THC-contaminated CBD products: Avoid
  • Kratom: Avoid (theoretical)
  • Antiparkinson drugs (levodopa, amantadine, pramipexole): Monitor
  • Beta-blockers (propranolol, bisoprolol, metoprolol): Monitor
  • Anesthesia and procedural sedation (propofol, midazolam, inhaled anesthetics): Monitor (theoretical)
  • Other sedating prescription drugs (zolpidem, trazodone, mirtazapine, quetiapine): Caution (theoretical)
  • Over-the-counter sedating antihistamines (diphenhydramine, doxylamine): Caution (theoretical)
  • Sedative supplements (kava, valerian, melatonin, passionflower): Caution (theoretical)
    •

Risk & Side Effects

  • High:
  • Medium:
  • Low: Tolerance, dependence and withdrawal; sedation, respiratory depression and coma; agitation, delirium and psychosis; involuntary movements; rapid heart rate and blood pressure changes; liver fat accumulation; impaired coordination and driving; gastrointestinal distress
    •
  • Speculative:

Monitoring

Marker Target Why
ALT and AST ALT about 7–56 U/L; AST about 10–40 U/L Safety check: liver warning on fact sheets
Creatinine with eGFR Creatinine about 0.6–1.3 mg/dL; eGFR: no established target, track change from own baseline Safety check: elimination via the kidneys
Resting heart rate 60–100 beats per minute Safety check: rapid heart rate signals toxicity
GAD-7 score No established target; track change from own baseline Expected to change: anxiety
Insomnia Severity Index No established target; track change from own baseline Expected to change: sleep

Cadence: Baseline before starting; questionnaires at 2 and 4 weeks, then at the end of each course; liver enzymes, kidney function and heart rate every 4–6 weeks during continuous use

Qualitative Assessment

  • Subjective sleep quality and ease of falling asleep
  • Daytime alertness and absence of grogginess
  • Anxiety level between doses, as an early sign of rebound
  • Need to raise the dose for the same effect
  • Mood, irritability and motor coordination
  • Mental clarity and concentration
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.