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    Disclaimer
    ☠ This is an extremely potent opioid active in microgram doses. Accidental overdose can be rapidly fatal. Naloxone should always be on hand.
    🧪 This is a research chemical with limited data on its long-term health effects, toxicity profile, and safe dosage ranges.

    4-Methoxybutyrfentanyl Encyclopedic
    Encyclopedic
    Typical encyclopedia coverage. Cross-reference for important decisions.
    • 3 corroborating sources
    • 3 ROAs with full dose ladders
    • duration data present
    • 19 combo interactions documented
    • classified Tentative
    • classified Research-chemical
    • dose data not in PW/TripSit (unverifiable)

    Aliases: 4-meo-bf, 4-meo-butryfentanyl, 4-MeO-Butyrfentanyl

    Depressant Research-chemical Opioid

    Summary TheDrug.Wiki TripSit

    4-MeO-BF is a highly potent fentanyl analogue first identified in Europe in 2015. Fatal blood concentrations have ranged 2-18 ng/mL, only modestly lower than fentanyl itself. Street material varies wildly in purity; volumetric dosing with a 1 mg/mL (or weaker) solution and a 0.01 mL oral syringe is strongly advised - never eyeball powder.

    Dose Information TheDrug.Wiki

    ROA Light Common Strong Heavy
    Oral 50-100µg 100-300µg 300-600µg 600µg+
    Insufflated 25-75µg 75-200µg 200-400µg 400µg+
    Intravenous 10-25µg 25-75µg 75-150µg 150µg+
    Light Common Strong Heavy

    Onset, Duration & After-effects TheDrug.Wiki

    ROA Onset Peak Offset After Effects Total
    Oral 5-15 min 15-45 min 15-45 min 1-2 hrs 0.5-2 hrs
    Insufflated 5-15 min 15-45 min 15-45 min 1-2 hrs 0.5-2 hrs
    Intravenous 5-15 min 15-45 min 15-45 min 1-2 hrs 0.5-2 hrs

    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 7.6
    Intense 8/10

    Strong euphoria and pain relief with moderate itching/nausea, low sedation

    Euphoria / Warmth ×3
    10
    physical euphoria cognitive euphoria euphoria warmth mood lift
    Analgesia ×2
    8
    pain relief analgesia
    Sedation / Relaxation ×1
    3
    sedation
    ⚠ Itching / Nausea ×1
    6
    nausea constipation
    Based on reports from:
    Erowid Experience Reports PsychonautWiki 4-Methoxybutyrfentanyl
    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 3d Half tolerance 14d Baseline ~28d

    Opioid tolerance builds rapidly with daily/frequent exposure and decays over weeks; risk of overdose is highest after abstinence due to loss of tolerance. Data specific to 4‑MeO‑BF are sparse; estimates extrapolated from fentanyl-class opioids.

    Cross-Tolerances

    all µ‑opioid agonists (fentanyl, morphine, oxycodone, heroin, etc.)
    70%

    Effects TheDrug.Wiki

    Positive
    • Anxiolysis
    • Pain relief
    • Physical euphoria
    • Cough suppression
    • Analgesia
    Negative
    • Respiratory depression
    • Nausea
    Neutral
    • Sedation
    • Itchiness
    • Pupil constriction
    Positive
    • Cognitive euphoria
    • Reduced anxiety
    • Euphoria
    • Anxiety suppression
    • 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 4-Methoxybutyrfentanyl with another substance

    4-Methoxybutyrfentanyl's nerd page Pharmacology, chemical data, effect profiles, and more
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    Helpful Links

    📘 Experience Reports 📖 TheDrug.Wiki 📖 PsychonautWiki