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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.
    • 4 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 dose.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 dose.wiki Drugs.Wiki

    Dose basis. The dose figures on this page are not clinical data. They are aggregated from community reports by a secondary source whose own notes state there is no human pharmacokinetic study behind them, and our internal audit flags this substance's dosing as unverifiable. Treat them as a rough orientation, not a safe range. This is a microgram-active opioid: a normal milligram scale cannot weigh a dose of it accurately, and a weighing error here is measured in lethal multiples rather than percentages. Volumetric dosing is the only defensible method, and batch-to-batch potency in the unregulated supply varies enormously. 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
    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 dose.wiki Drugs.Wiki

    ROA Onset Peak Offset After Effects Total
    Oral 5-15 min 15-45 min 15-45 min 1-2 hrs 0.58-1.75 hrs
    Insufflated 1-2 min 15-45 min 15-45 min 1-2 hrs 0.52-1.53 hrs
    Intravenous 1 min 15-45 min 15-45 min 1-2 hrs 0.51-1.52 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
    View methodology →

    Add to PsychonautWiki Journal

    The PsychonautWiki Journal logging app doesn't include every substance. To track 4-Methoxybutyrfentanyl there, start adding an ingestion, search for the name, and choose to add it as a custom substance. Paste these values:

    ⬇ Download import file Import this file as custom substances and you get "4-Methoxybutyrfentanyl (Substance Search)" with every route's full dose ladder and timeline, no typing. Works on iOS and Android (v15+); the format is confirmed by the app's developer. The manual values below work for older versions.
    Name
    4-Methoxybutyrfentanyl
    Unit
    µg
    Description 
    4-Methoxybutyrfentanyl
Source: SubstanceSearch (substancesearch.com)

Oral dose (µg): threshold 50 (unverified) · light 50-100 · common 100-300 · strong 300-600 · heavy 600+
Insufflated dose (µg): threshold 25 (unverified) · light 25-75 · common 75-200 · strong 200-400 · heavy 400+
Intravenous dose (µg): threshold 10 (allergy test) · light 10-25 · common 25-75 · strong 75-150 · heavy 150+

Oral duration: onset 5-15m · peak 15-45m · offset 15-45m · total 0.58-1.75h · after-effects 1-2h
Insufflated duration: onset 1-2m · peak 15-45m · offset 15-45m · total 0.52-1.53h · after-effects 1-2h
Intravenous duration: onset 1m · peak 15-45m · offset 15-45m · total 0.51-1.52h · after-effects 1-2h

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 ~ 200 µg (Oral).

    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

    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 dose.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

    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 📖 dose.wiki 📖 PsychonautWiki