OxyContin contributed to a modern opioid epidemic with lasting repercussions, and now fentanyl has brought the overdose crisis to a new level.

Although both are highly addictive opioids (a class of drugs with pain-relieving and euphoria-inducing properties), fentanyl is purely synthetic, meaning it can be made easily and cheaply in a lab, and it is more potent—about 50 to 100 times stronger—than many prescription opioids.

In 2022, according to provisional data from the Centers for Disease Control and Prevention (CDC), close to 83,000 people died from opioid overdoses in the United States, the majority from fentanyl and other highly potent synthetic substances.

Fentanyl isn’t new; it has been used in the U.S. since 1960 as an intravenous anesthetic. It is still prescribed today by doctors, often in the form of patches and lozenges, for treating severe and chronic pain from cancer and other illnesses and injuries.

But fentanyl has shifted from exclusively being produced by pharmaceutical companies to now also coming from drug cartels and other entities, says David Fiellin, MD, a Yale Medicine primary care physician who specializes in addiction medicine. “We refer to it as illicitly manufactured fentanyl,” he says. Read more at Yale Medicine.