4-Methoxybutyrfentanyl
Aliases: 4-meo-bf, 4-meo-butryfentanyl, 4-MeO-Butyrfentanyl
Categories
Summary
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. Naloxone 0.4-2 mg IV/IM will reverse toxicity, but its shorter half-life means repeat doses or continuous infusion may be required (re-narcotization common after 30-60 minutes). Always monitor at least 2 hours after last dose.
Dose Information
| ROA | Light | Common | Strong | Heavy |
|---|---|---|---|---|
| Oral | 50-100ug | - | - | - |
| Insufflated | 25-75ug | - | - | - |
| Intravenous | 10-25ug | - | - | - |
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| 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 |
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
Effects
Positive
- Anxiolysis
- Pain relief
- Physical euphoria
- Cough suppression
- Analgesia
Negative
- Respiratory depression
- Nausea
- Sedation
- Itchiness
- Pupil constriction
Positive
- Cognitive euphoria
- Reduced anxiety
- Euphoria
- Anxiety suppression
- Mood lift
Negative
- Constipation
- Compulsive redosing
- Dizziness
- Motor control loss
- Physical autonomy
Positive
- Warmth
- Color enhancement
- Increased music appreciation
- Brightened colour
Negative
- Light sensitivity
- Appetite suppression
- Disinhibition
- Dehydration
- Dulled perception
- Drifting