4-Methoxybutyrfentanyl - Substance Search

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	50-100ug	-	-	-
Insufflated	25-75ug	-	-	-
Intravenous	10-25ug	-	-	-

Light Common Strong Heavy

Onset, Duration & After-effects TheDrug.Wiki

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

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.