Alfentanil
Encyclopedic
Encyclopedic
Typical encyclopedia coverage. Cross-reference for important decisions.
- 2 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 19 combo interactions documented
- PubChem toxicity data
- dose data not in PW/TripSit (unverifiable)
- 2 corroborating sources
- 1 ROA with full dose ladder
- duration data present
- 19 combo interactions documented
- PubChem toxicity data
- dose data not in PW/TripSit (unverifiable)
Aliases: Alfenta, Rapifen, R-39209
Summary
Alfentanil is a short-acting synthetic opioid analgesic approximately one-quarter to one-tenth the potency of fentanyl, with a rapid onset (1-2 minutes) and brief duration (30-60 minutes). Almost exclusively used in controlled medical anesthesia settings for surgical procedures requiring precise, short-term analgesia. Carries extreme risk of life-threatening respiratory depression, particularly when combined with other CNS depressants.
Dose Information
Dose basis. The dose figures on this page come from clinical practice, where this drug is given by trained staff who are titrating to effect with airway support and monitoring immediately available. They are not a self-administration guide, and the margin they assume does not exist outside that setting. Assume full respiratory depression, keep naloxone to hand, never dose alone, and never combine with benzodiazepines, alcohol or other depressants.
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Intravenous | 4-8µg/kg | 8-20µg/kg | 20-40µg/kg | 40µg/kg+ |
Onset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset | Total |
|---|---|---|---|---|---|
| Intravenous | 1-2 min | 2-5 min | 5-15 min | 15-30 min | 23-52 min |
Effect Profile
Scores (1–10) curated from multiple sources:
- Effect keyword matching from PsychonautWiki catalog
- Weighted by importance: core (×3), major (×2), minor (×1)
Strong euphoria and itching/nausea with mild sedation and pain relief
Add to PsychonautWiki Journal
The PsychonautWiki Journal logging app doesn't include every substance. To track Alfentanil there, start adding an ingestion, search for the name, and choose to add it as a custom substance. Paste these values:
Alfentanil Source: SubstanceSearch (substancesearch.com) Intravenous dose (µg/kg): threshold 2-4 · light 4-8 · common 8-20 · strong 20-40 · heavy 40+ Intravenous duration: onset 1-2m · come-up 2-5m · peak 5-15m · offset 15-30m · total 23-52m Note: ranges are harm-reduction guidance, not a prescription. Start low, go slow, and test your substances.
Tip: for quicker logging you can also add a Custom Unit in the app, e.g. common dose ~ 14 µg/kg (Intravenous).
The app keeps custom substances simple, so the full dose ranges live in the description text above. Ranges are harm-reduction guidance, not a prescription.
Tolerance
Tolerance Decay
Acute tolerance: develops within a single session — the reset numbers above apply after sustained heavy use, not after one binge. Within-session tachyphylaxis usually resets largely overnight.
Opioid tolerance to sedative/analgesic effects typically develops over days to weeks and decays over days to weeks after cessation; interindividual variability is high. Cross‑tolerance among µ‑agonists is substantial but not complete. Values here are approximations synthesized from clinical experience and reviews rather than alfentanil‑specific PK/PD studies.
Cross-Tolerances
Effects
- Pain relief
- Physical euphoria
- Muscle relaxation
- Cough suppression
- Respiratory depression
- Nausea
- Itching
- Sedation
- Pupil constriction
- Itchiness
- Euphoria
- Cognitive euphoria
- Anxiety suppression
- Reduced anxiety
- Mood lift
- Constipation
- Compulsive redosing
- Dizziness
- Motor control loss
- Physical autonomy
- Warmth
- Color enhancement
- Increased music appreciation
- Brightened colour
- Light sensitivity
- Appetite suppression
- Disinhibition
- Dehydration
- Dulled perception
- Drifting
Combinations
Cross-Check Alfentanil with another substanceHelpful Links
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