Alfentanil Encyclopedic

Encyclopedic

Typical encyclopedia coverage. Cross-reference for important decisions.

2 corroborating sources

1 ROA with full dose ladder

duration data present

29 combo interactions documented

PubChem toxicity data

dose data not in PW/TripSit (unverifiable)

Aliases: Alfenta, Rapifen, R-39209

Summary dose.wiki

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.

Dose Information Drugs.Wiki

Dose basis. The dose figures on this page come from clinical practice, where this drug is given by trained staff who are titrating to effect with airway support and monitoring immediately available. They are not a self-administration guide, and the margin they assume does not exist outside that setting. 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
Intravenous	4-8µg/kg	8-20µg/kg	20-40µg/kg	40µg/kg+

Light Common Strong Heavy

Sources

Intravenous

Dose ladder — Drugs.Wiki

Onset, Duration & After-effects dose.wiki Drugs.Wiki

ROA	Onset	Comeup	Peak	Offset	Total
Intravenous	1-2 min	2-5 min	5-15 min	15-30 min	23-52 min

Effect Profile

Scores (0–10) curated from multiple sources:

Effect keyword matching from PsychonautWiki catalog
Weighted by importance: core (×3), major (×2), minor (×1)

Full methodology

Opioid 6.1

Strong 6/10

Strong euphoria with strong itching/nausea, mild sedation and pain relief

Euphoria / Warmth ×3

physical euphoria euphoria cognitive euphoria mood lift

Analgesia ×2

pain relief

Sedation / Relaxation ×1

sedation muscle relaxation

⚠ Itching / Nausea ×1

itching nausea constipation

Tolerance

Build-up develops within days of regular use; analgesic tolerance faster than respiratory depression tolerance

Reset Falls quickly once you stop, at a rate you can't judge. After any break, treat your tolerance as gone.

No tolerance chart. Our decay curves for opioids were estimates, and a curve can make tolerance look longer-lasting than it is, which is the dangerous direction.

Opioid tolerance drops fast when you stop, and even a few days off can be enough, so a dose that used to be normal can now stop your breathing. Overdose deaths rise sharply after prison, detox or leaving treatment, and tolerance also falls during a hospital stay. After any break, start with a much smaller amount, try a test dose first, don't use alone, and keep naloxone within reach. Alcohol, benzodiazepines, gabapentinoids and other sedatives make an opioid overdose much more likely.

Sources: FRANK: heroin · National Harm Reduction Coalition · WHO: opioid overdose · Merrall et al. 2010 · Binswanger et al. 2007 · Strang et al. 2003 · FDA 2019: gabapentinoids and breathing

Cross-Tolerances

Other opioids (fentanyl, morphine, oxycodone, etc.)

Effects dose.wiki

Positive

Negative

Neutral

Positive

Negative

Neutral

Combinations

Cross-Check Alfentanil with another substance

Alfentanil's nerd page Pharmacology, chemical data, effect profiles, and more

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Helpful Links

💊 Pill Identifier 📖 dose.wiki

Add to PsychonautWiki Journal

The PsychonautWiki Journal logging app doesn't include every substance. To track Alfentanil 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 "Alfentanil (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

Alfentanil

Unit

µg/kg

Description

Alfentanil
Source: SubstanceSearch (substancesearch.com)

Intravenous dose (µg/kg): threshold 2-4 · light 4-8 · common 8-20 · strong 20-40 · heavy 40+

Intravenous duration: onset 1-2m · come-up 2-5m · peak 5-15m · offset 15-30m · total 23-52m

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 ~ 14 µg/kg (Intravenous).

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.

Report an issue or suggest an edit

Spotted incorrect or dangerous information, have a correction, a new study, or a useful addition for Alfentanil? Let us know. Reports are reviewed by moderators — this is not posted publicly.

Alfentanil Encyclopedic Encyclopedic Typical encyclopedia coverage. Cross-reference for important decisions. 2 corroborating sources 1 ROA with full dose ladder duration data present 29 combo interactions documented PubChem toxicity data dose data not in PW/TripSit (unverifiable)