Carfentanil
Limited data
Limited data
Sparse data. Doses and effects may be unreliable or untested.
- 1 source
- duration data present
- 1 source
- duration data present
Aliases: Carfentanyl, Wildnil, R-33799, 4-methoxycarbonylfentanyl
Summary
Carfentanil is an ultra-potent synthetic opioid of the 4-anilidopiperidine class, estimated at roughly 10,000x the potency of morphine and ~100x that of fentanyl. It has NO recognised human therapeutic or recreational dose — it is used in veterinary medicine to immobilise large animals (brand name Wildnil). Microgram-level exposure can cause fatal respiratory depression. Carfentanil is increasingly found as an adulterant or substitute in the illicit opioid supply (often pressed into counterfeit pills or mixed into heroin/fentanyl), so exposure is frequently unintentional. Treat any suspected exposure as a medical emergency: give naloxone (repeated/large doses are often required), call emergency services, and monitor for prolonged or recurrent respiratory depression.
Dose Information
“Microgram-level exposure can cause fatal respiratory depression.” — encyclopedia summary
Onset, Duration & After-effects
| ROA | Onset | Peak | Offset |
|---|---|---|---|
| Oral | Seconds to minutes | Minutes | - |
| Insufflated | Seconds to minutes | Minutes | - |
Effect Profile
Scores (0–10) curated from multiple sources:
- Effect keyword matching from PsychonautWiki catalog
- Weighted by importance: core (×3), major (×2), minor (×1)
Moderate sedation with moderate itching/nausea, mild pain relief
Tolerance
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
Effects
Effect glossary — · full glossary
Helpful Links
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