Phenazepam
Aliases: Fenaz, Panda, Bonsai, Soviet benzo, Bromdihydrochlorphenylbenzodiazepine
Summary
Phenazepam is an extremely potent, long-acting benzodiazepine developed in the Soviet Union in 1975, reportedly 5-10 times stronger than diazepam. Its extremely long half-life and delayed onset of peak effects create severe risks: users often redose before feeling effects, leading to dangerous accumulation and blackouts lasting days or weeks. Not approved in most Western countries but sometimes sold online or found in counterfeit pharmaceuticals.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 0.5-1mg | 1-2mg | - | 2-4mg+ |
| Sublingual | 0.5-1mg | 1-2mg | - | 2-4mg+ |
Benzo Equivalence Calculator
| Substance | Equivalent Dose | Potency |
|---|
⚠ These are approximate equivalences for educational and cross-tapering reference. Individual response, tolerance, and half-life differences mean actual equivalence varies. Always consult a healthcare provider for tapering guidance.
Onset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset | Total |
|---|---|---|---|---|---|
| Oral | 20-60 min | 1-3 hrs | 2-4 hrs | 24-72 hrs | 27.3-80 hrs |
| Sublingual | 15-45 min | 30-90 min | 2-4 hrs | 24-72 hrs | 26.8-78.2 hrs |
| Insufflated | 10-30 min | 30-90 min | 2-4 hrs | 24-72 hrs | 26.7-78 hrs |
Effect Profile
11 reportsScores (1–10) curated from multiple sources:
- Effect keyword matching from PsychonautWiki catalog
- Weighted by importance: core (×3), major (×2), minor (×1)
Strong anxiolysis and cognitive impairment with moderate euphoria, mild sedation
Tolerance
Tolerance Decay
Based on general benzodiazepine patterns and user reports: noticeable tolerance can develop with repeated use over days to weeks; partial reversal over 2–4 weeks of abstinence. Individual variability is high; data are anecdotal.
Cross-Tolerances
Effects
Aggregated from 11 Erowid experience reports