Why is fentanyl so deadly? What was it originally for?

In the early 1960s the synthetic opioid was manufactured and approved by the FDA a few years later, for a specific purpose: to treat pain.

Why fentanyl is deadlier than heroin, in a single photo - STAT

A grain of sand: Why fentanyl is so deadly

Why is fentanyl so deadly?

Fentanyl, Inc.' Tracks Opioid's Dark Web Path From China To U.S.

If You Can See It, It Can Kill You

Why is Fentanyl so Dangerous? - Drug Rehab & Drug Detox Treatment

How Deadly is Fentanyl and Why Is It So Dangerous

Fentanyl is so potent doctors don't know how to fight it

Fentanyl: 5 things you need to know

5 things everyone should know about fentanyl

Fentanyl: America's struggle to contain a deadly drug

Teenage Fentanyl Deaths Are Soaring, and Black Teens Are Hit