Carfentanil-Involved Drug Overdoses Soar From 2023 to 2024

The number of drug overdose deaths involving illegally manufactured fentanyl and fentanyl analogs (IMFs) dropped in the United States during the latter portion of 2023. But a new report from the Centers for Disease Control and Prevention (CDC) suggests that an increase in overdoses involving the potent fentanyl analog carfentanil threatens to undo that progress.

Overdose deaths from carfentanil rose by more than 700% in the past year, increasing from 29 between January and June 2023 to 238 in that same period in 2024. 

Carfentanil is used as a tranquilizing agent for elephants and other large mammals and is 100 times more potent than fentanyl. Just 2 mg can be lethal to humans, and a carfentanil-related overdose can require more than three shots of naloxone to reverse. 

Prior to this resurgence of carfentanil, the drug “had largely disappeared after carfentanil-involved overdose death outbreaks in 2016-2017,” study authors noted, when carfentanil overdose deaths topped 1200, other data showed. 

“Educational and response efforts that can rapidly adapt to the potential for increased distribution of drugs more potent than fentanyl, such as carfentanil, are needed and might avert or mitigate new increases in overdose deaths,” the authors wrote. 

The findings were published online on December 5 in CDC’s Morbidity and Mortality Weekly Report.

Carfentanil May Stall Overdose Decline

IMFs such as carfentanil were first detected in the United States illegal drug supply in 2013. A little more than a decade later, IMFs have replaced heroin as the most common opioid in the United States.

The introduction of IMFs led to a sharp rise in overdose deaths, but provisional data suggest these fatalities are on the decline. A recent re-emergence of carfentanil could stall that downward trend.

To investigate further, researchers used data from the CDC’s State Unintentional Drug Overdose Reporting System to analyze detection of IMFs and carfentanil between January 2021 and June 2024. 

The database houses information on drug overdoses obtained from death certificates, coroner and medical examiner reports, and postmortem toxicology reports from 49 states and the District of Columbia.

From January 2021 to December 2023, more than 251,000 people died from drug overdoses with unintentional and undetermined intent, 75% of which involved IMFs. 

IMF-linked deaths peaked at 16,814 in the second quarter of 2023, then declined by nearly 16% to 14,299 deaths by the end of that year.

Investigators could only speculate on the reasons for the decline in overdoses. It is possible that drug users are mixing fentanyl with other drugs, such as xylazine, which may reduce the danger of fatal overdose. It’s also possible that overdose prevention programs are partially responsible for the decline.

“Continued and expanded implementation of these programs, including naloxone distribution and increasing access to treatments for substance use disorders, might result in sustained and continued declines in drug overdose deaths,” they wrote.

Regional Differences

When researchers analyzed the results by region, they found that IMFs were detected in 81.5% of overdose deaths in the Northeast, 75% in the Midwest, and 75% in the Southern regions during the study period. These percentages were relatively stable until summer 2023, when declines in IMF-linked overdoses were noteworthy.

Specifically, deaths due to IMFs decreased 11% in the Northeast (8245 to 7323), 16% in the Midwest (7160 to 6008), and 10.5% in the South (13,492 to 12,077).

In the West, however, overdoses linked to IMFs increased by 66.5% between 2021 and the second quarter of 2024. 

The researchers speculated that the surge in the Western United States could be due to fentanyl entering the drug markets in that region later than in other areas, “likely because of challenges of mixing fentanyl into the black tar heroin that was more common in the West,” they wrote.

The findings suggest that, despite overall declines in overdose deaths reported nationwide, “recent sharp increases in overdose deaths with carfentanil detected, although rare, highlight the ever-changing illegal drug supply and threaten progress in reducing overdose deaths,” the authors wrote.

The report authors encouraged expanding education programs for the public about the dangers of carfentanil and other IMFs, as well as harm reduction strategies, including using fentanyl test strips or drug checking services.

There was no study funding information available. There were no relevant financial relationships.