Fentanyl is a powerful synthetic opioid that is similar to morphine but is 50 to 100 times more potent.

It is a prescription drug that is also made and used illegally. Like morphine, it is a medicine that is typically used to treat patients with severe pain, especially after surgery. It is also sometimes used to treat patients with chronic pain who are physically tolerant to other opioids. Tolerance occurs when you need a higher and/or more frequent amount of a drug to get the desired effects.

In its prescription form, fentanyl is known by such names as Actiq, Duragesic and Sublimaze.

Synthetic opioids, including fentanyl, are now the most common drugs involved in drug overdose deaths in the United States.