Drug More Powerful Than Fentanyl Detected in 37 States

Overdose deaths due to carfentanil—a dangerous drug more potent than fentanyl—are becoming more common, according to a recent report from the Centers for Disease Control and Prevention (CDC).

The U.S. has grappled with an opioid crisis for decades, with thousands of overdose deaths reported each year. But a report published on Dec. 5 in the CDC’s Morbidity and Mortality Weekly Report showed that opioid overdose deaths are finally on the decline. The percentage of deaths caused by illegally manufactured fentanyl has also dropped slightly.

However, the report authors warned that there appears to be a “reemergence” of a synthetic opioid called carfentanil—deaths caused by the drug have increased seven-fold, which could “threaten this progress” the country is seeing otherwise.

The report found that deaths from carfentanil increased by more than 720% from the first half of 2023 compared to the first half of 2024.

These deaths have been reported in 37 states, meaning the drug is relatively widespread in the U.S. Eight states—New York, Maryland, Florida, Illinois, Michigan, Ohio, West Virginia, and Kentucky—have each reported over 20 carfentanil-related deaths.

Carfentanil isn’t as well known to the public as fentanyl is, and carfentanil-related overdose deaths are still considered “rare,” per the report. The drug was linked to 513 overdose deaths between January 2021 and June 2024.

But the extreme jump in cases is troubling, experts told Health. Here’s what to know about carfentanil, how it compares to other dangerous drugs, and whether it could impact the U.S. opioid crisis overall.

Carfentanil is a synthetic opioid that is traditionally used as a tranquilizer for elephants and other large animals, Diane Calello, MD, executive medical director of the New Jersey Poison Information and Education System and professor at the Rutgers New Jersey Medical School, told Health.

The drug was first created in the 1970s and is sold under the name Wildnil.

Opioids, in small doses, can relieve pain and cause relaxation, Calello explained. However, unlike fentanyl and oxycodone, “carfentanil is not used for pain control in humans,” she said.

Carfentanil is 100 times more potent than fentanyl and 10,000 times more potent than morphine, so “even a small amount can cause overdose and death,” said Hawre Jalal, MD, PhD, Canada research chair in health economics and associate professor of epidemiology and public health at the University of Ottawa.

“Carfentanil, like fentanyl, crosses the blood-brain barrier and binds to mu-opioid receptors in the brain, which are responsible for pain relief and euphoria,” Jalal told Health. “However, carfentanil binds much more strongly than naturally occurring endorphins or other opioids, making it significantly more dangerous.”

When someone is exposed to carfentanil, they’ll usually have trouble breathing and thinking, fall into a coma, and experience “respiratory arrest,” Calello said. In other words, the drug can cause people to stop breathing.

The body can start to have a reaction to carfentanil after being exposed to just one microgram—a minuscule amount.

The drug naloxone (also known as Narcan) can quickly reverse opioid overdoses and could counteract an overdose from carfentanil, said Jalal. However, these overdoses can be difficult to treat.

“Due to the drug’s extreme potency, multiple doses may be required in rapid succession, which reduces the likelihood of successful reversal,” he explained.

Exposures are also challenging to treat because of how quickly carfentanil works in the body, Calello said.

“Patients may die before they can receive treatment,” she explained.

Carfentanil “has no approved medical use in humans” but has seeped into the illegal drug trade, Jalal said. Unlike other drugs, though, “most cases of ingestion are likely accidental,” he explained.

“It is a contaminant or adulterant in the drug supply, meaning the person who is using it is not anticipating to be exposed to it,” Calello said.

People who overdose on carfentanil are usually exposed to the drug when they’re taking fentanyl, she added. According to the CDC’s report, from July 2023 to June 2024, nearly 87% of people who died from carfentanil also had illegally manufactured fentanyl in their system.

This differentiates the current trend from documented outbreaks of carfentanil overdose deaths back in 2016 and 2017, the report authors added.

Nearly a decade ago, states such as Florida and Ohio saw hundreds of carfentanil-related deaths, though just a quarter of them also involved fentanyl. But now, carfentanil overdoses are being seen in dozens of states and seem to occur with fentanyl use, which is cause for greater concern.

“The potential mixing of carfentanil into fentanyl products as an adulterant raises concern that its presence might be unknown to persons using drugs, reminiscent of the way that fentanyl was first introduced as an adulterant of heroin,” the report stated.

It’s not totally clear whether carfentanil deaths will continue to increase in the coming months or years, but experts have concerns.

In addition to the fact that people may be adding carfentanil to other illicit drugs, the widespread nature of these overdose deaths is worrying, said Jalal.

“During the 2016–2017 carfentanil outbreak, precursor chemicals from China fueled localized surges in overdose deaths,” he said. “After China regulated fentanyl in 2018, carfentanil-related deaths declined. The current outbreak appears more widespread, affecting 37 states, which poses greater challenges for controlling the supply and mitigating its impact on the opioid crisis.”

Still, it’s important to note that, for now, exposure to carfentanil is “much less common than fentanyl,” even though the former is more likely to cause an overdose, Calello noted.

However, if the situation changes and “carfentanil becomes a more common component of the illicit drug supply, opioid overdose deaths will increase and some of the progress which has been made will be undone,” she said.