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.

Fentanyl Invades More Illicit Pills, With Deadly Consequences - WSJ

Chinese suppliers flood US and Canada with deadly fentanyl

Nearly 70,000 People Died of Overdoses Involving Fentanyl in 1

Fentanyl Facts

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

What Is Fentanyl and Why Is It So Dangerous? - WSJ

Fentanyl: What is it, and why is it so dangerous

Visualizing fentanyl's swift, dangerous effects on the brain and body

The Fentanyl Epidemic: How and Why Fentanyl Became One of the Most

DEA Washington Division Announces the Seizure of Over 8 Million of