What Is Carfentanil? Elephant Tranquilizer Behind Rising U.S. Deaths

A drug that is 100 times more potent than fentanyl and 10,000 times stronger than morphine has been behind a rapidly increasing number of overdose deaths in the U.S., prompting concern from government agencies and public health experts.

Where a fatal dose of fentanyl is 2 milligrams, a lethal amount of carfentanil is only 0.2 milligrams.

“Because of this potency, even very small changes in the amount present in the drug supply can substantially increase overdose risk,” Dr. Hawre Jalal, a professor of health economics at the University of Ottawa, told Newsweek.

The DEA said the re-emergence of carfentanil is a “chilling reminder of how the opioid epidemic continues to evolve and introduces new threats at an alarming pace.”

Carfentanil Deaths Are Rising Rapidly Across the U.S., CDC Data Shows

According to the Centers for Disease Control and Prevention (CDC), deaths involving carfentanil increased by around sevenfold between 2023 and 2024-going from 29 deaths from January to June 2023, to 238 deaths from January to June 2024.

Carfentanil-also known as an elephant tranquilizer because it is sometimes used in veterinary settings for very large animals-had been detected in 37 states by May 2025, according to the United States Drug Enforcement Administration (DEA).

What Is Carfentanil, the Ultra‑Potent Opioid Behind New Overdose Surges?

Carfentanil is a fentanyl analog, meaning that while the synthetic opioid may seem to resemble fentanyl, its chemical structure differs, and its potency is significantly higher.

“Fentanyl itself is already highly potent and dangerous, but carfentanil is exceptionally potent and has no medical use in humans,” Jalal said, adding that one of the main dangers of the drug is that “people using drugs may not know carfentanil is present, and accurate dosing in illicit markets is extremely difficult.”

According to the DEA, carfentanil has been found to be mixed with other drugs or pressed into pills that look like prescription painkillers, in an effort to increase drug potency and profits.

Why Naloxone May Not Always Stop a Carfentanil Overdose

Symptoms of carfentanil exposure usually begin within minutes and can include respiratory depression or arrest, drowsiness, disorientation, sedation, pinpoint pupils, and clammy skin.

As the drug has such a rapid effect on the central nervous system, it leaves little time for life-saving interventions, so treating an overdose involving carfentanil is extremely difficult, the DEA said.

Naloxone, which is widely used as an emergency antidote for opioid overdoses, may not be effective against carfentanil in normal doses, but even in multiple, higher doses, “effective reversal of an overdose is not guaranteed,” the DEA added.

Because of its potency, the CDC has warned that the emergence of carfentanil might “threaten” the progress made in bringing down overdose deaths associated with illegally manufactured fentanyl and fentanyl analogs.

Why Carfentanil Is Re‑Entering the U.S. Drug Supply

Jalal said he thought “carfentanil's re-emergence reflects how quickly illicit opioid markets can change,” explaining these markets have “strong incentives to use compact, potent, and easily trafficked synthetic opioids,” and that when supply chains are “disrupted, or when traffickers adapt to enforcement pressure, the market can shift rapidly.”

He added that China may play an “important” role in this, as in 2017, China scheduled carfentanil and several other fentanyl analogs as controlled substances, effective March 1, 2017.

He said that he and a colleague examined the 2016 to 2018 spike and subsequent decline in carfentanil overdose deaths and found that the rise and fall of carfentanil availability appeared to be highly localized – concentrated in Ohio, Florida, Pennsylvania, Kentucky, and Michigan – and the 2018 decline in overdose deaths in those states accounted for nearly all of the national decline that year.

In his research, he said he found that “China's regulatory action coincided with a sharp decline in carfentanil exhibits, particularly in Ohio, and with a decline in carfentanil-involved mortality in places such as Wayne County, Michigan.”

“This does not prove causality, but it suggests that international regulation of synthetic opioids and precursor supply chains can have rapid effects on local illicit drug markets and overdose mortality,” he added.

What Public Health Experts Say Can Reduce the Risk

Jalal said it “concerns” him that carfentanil is re-emerging. He added that Americans should understand that carfentanil is “not something a person can reliably detect by appearance, taste, or prior experience with fentanyl.”

“The drug supply is unpredictable and can change rapidly,” he said. “This reinforces the importance of naloxone availability, not using alone, drug checking where available, and expanding access to evidence-based treatment for opioid use disorder.”

The DEA also advises that Americans should “refrain from using illicit drugs, as they may contain carfentanil without your knowledge,” and to “never take a pill that was not prescribed to you by a doctor and dispensed by a licensed pharmacist.”

The agency adds that “if you suspect someone has been exposed to carfentanil or is experiencing symptoms of overdose, call emergency services immediately and administer naloxone, if available.”

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This story was originally published April 29, 2026 at 12:08 PM.