Substance guides

What is carfentanil? The elephant tranquilizer in the drug supply

Published November 14, 2024 · 6 min read · Updated April 2026

Reviewed for accuracy by licensed clinical professionals.

Carfentanil is a synthetic opioid approximately 10,000 times more potent than morphine and 100 times more potent than fentanyl. It is approved only for tranquilizing large animals.

Why it is in the drug supply

Extreme potency means tiny amounts produce effects, making it highly profitable. It is sometimes mixed into heroin or pressed into counterfeit pills. Amounts invisible to the naked eye can be lethal.

The danger

The lethal dose is measured in micrograms, invisible to the human eye. Standard doses of naloxone may not be sufficient to reverse carfentanil overdose. Multiple naloxone doses may be needed. First responder contamination risk is a concern.

Protection

The same harm reduction strategies apply: never use alone, carry naloxone (multiple doses), use fentanyl test strips (which also detect carfentanil), and start with tiny test doses.

Authoritative sources

This article references guidelines from: SAMHSA · NIDA · ASAM

Frequently asked questions

How strong is carfentanil?

10,000 times more potent than morphine and 100 times more potent than fentanyl.

Is carfentanil in street drugs?

It has been detected in heroin and counterfeit pills, though it is less common than regular fentanyl.

Can naloxone reverse carfentanil overdose?

Naloxone works but multiple doses may be needed due to carfentanil's extreme potency.

Disclaimer: Informational only. Not medical advice. SAMHSA: 1-800-662-4357.