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    ☠ This is an extremely potent opioid active in microgram doses. Accidental overdose can be rapidly fatal. Naloxone should always be on hand.

    Alfentanil Encyclopedic
    Encyclopedic
    Typical encyclopedia coverage. Cross-reference for important decisions.
    • 1 source
    • 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

    Depressant Opioid

    Summary TheDrug.Wiki

    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 TheDrug.Wiki

    ROA Light Common Strong Heavy
    Intravenous 4-8µg/kg 8-20µg/kg 20-40µg/kg 40µg/kg+
    Light Common Strong Heavy

    Onset, Duration & After-effects TheDrug.Wiki

    ROA Onset Peak Offset Total
    Intravenous 1-2 min 5-15 min 30-60 min 30-60 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)

    Full methodology

    Opioid 6.1
    Strong 6/10

    Strong euphoria and itching/nausea with mild sedation and pain relief

    Euphoria / Warmth ×3
    10
    physical euphoria euphoria cognitive euphoria warmth mood lift
    Analgesia ×2
    4
    pain relief
    Sedation / Relaxation ×1
    5
    sedation muscle relaxation
    ⚠ Itching / Nausea ×1
    10
    itching nausea constipation
    Based on reports from:
    Erowid Experience Reports PsychonautWiki Alfentanil
    View methodology →

    Tolerance

    Build-up develops within days of regular use; analgesic tolerance faster than respiratory depression tolerance
    Reset 7–14 days for partial reset; full reset may take weeks — tolerance loss greatly increases overdose risk

    Tolerance Decay

    Full tolerance 7d Half tolerance 7d Baseline ~35d

    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

    Other opioids (fentanyl, morphine, oxycodone, etc.)
    70%

    Effects TheDrug.Wiki

    Positive
    • Pain relief
    • Physical euphoria
    • Muscle relaxation
    • Cough suppression
    Negative
    • Respiratory depression
    • Nausea
    • Itching
    Neutral
    • Sedation
    • Pupil constriction
    • Itchiness
    Positive
    • Euphoria
    • Cognitive euphoria
    • Anxiety suppression
    • Reduced anxiety
    • Mood lift
    Negative
    • Constipation
    • Compulsive redosing
    • Dizziness
    • Motor control loss
    Neutral
    • Physical autonomy
    Positive
    • Warmth
    • Color enhancement
    • Increased music appreciation
    • Brightened colour
    Negative
    • Light sensitivity
    • Appetite suppression
    • Disinhibition
    • Dehydration
    Neutral
    • Dulled perception
    • Drifting

    Combinations TripSit

    Cross-Check Alfentanil with another substance

    Alfentanil's nerd page Pharmacology, chemical data, effect profiles, and more
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    Helpful Links

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