Summary
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. Classified as Schedule II in the United States due to high abuse potential and risk of fatal overdose.
Dose Information
Light
Common
Strong
Heavy
Onset, Duration & After-effects
| ROA | Onset | Comeup | Peak | Offset |
|---|---|---|---|---|
| Intravenous | 1-2 min | 2-5 min | 5-15 min | 15-30 min |
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
- Pain relief
- Physical euphoria
- Muscle relaxation
- Cough suppression
Negative
- Respiratory depression
- Nausea
- Itching
- Sedation
- Pupil constriction
- Itchiness
Positive
- Euphoria
- Cognitive euphoria
- Anxiety suppression
- Reduced anxiety
- 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