By Deidre McPhillips and Annette Choi, February 8th, 2025 | From: CNN

Fentanyl is powerful synthetic opioid that can be up to 100 times more potent than morphine.

It can be prescribed in formal medical settings to relieve severe pain and treat breakthrough pain when longer-acting pain medications aren’t enough. Injections may be used during or after surgery, for example, while patches help treat persistent pain in patients that may have become tolerant to other treatments. It can also be administered through a lozenge.

But fentanyl has become the most common drug involved in overdose deaths in the United States, fueling what the US Centers for Disease Control and Prevention has identified as the “third wave” of the opioid overdose epidemic. Fentanyl is relatively cheap to make, and its high potency means that supply can stretch far, making it an attractive option in the illicit market. Illicit fentanyl is typically found in powder form or pressed into counterfeit pills that look like prescription opioids. It can also be mixed into other drugs such as heroin to raise the potency at lower cost.

President Donald Trump is using the drug epidemic as a key justification for tariffs on goods from Mexico, Canada and China; a fact sheet from the administration says that “the flow of contraband drugs like fentanyl to the United States, through illicit distribution networks, has created a national emergency, including a public health crisis.” Tariffs on Mexico and Canada were put on hold for 30 days after the countries pledged to bolster border security, but a 10% tariff on goods from China took effect in early February.

The US imports the vast majority of medical fentanyl from China, which is shipped directly in finished form.

The illicit supply of fentanyl in the US also originates in China. At first, the illicit supply would also ship directly from China to the US, but it’s evolved into disparate streams. Now, there is no evidence that legal fentanyl is being diverted to the black market. Large shipments of precursor ingredients for illicit fentanyl are sent from China to Mexico, where they are processed in labs and the final product is smuggled over the border into the US.

Most of the precursor ingredients “are pretty basic chemicals with wide-scale applications, so hiding the shipments is not very complicated,” said Vanda Felbab-Brown, a senior fellow at the Brookings Institute who has led various initiatives centered on the opioid epidemic and global drug policy.

Mexican cartels then rely on established routes for drug trafficking that have been in place for a long time, often through legal ports of entry using US citizens that are recruited as mules.

Nearly 22,000 pounds of fentanyl were seized at US borders during the 2024 fiscal year, according to data from the US Customs and Border Protection. Nearly all of it – about 97% – was confiscated along the southwest border, with seizures in Tucson, Arizona, accounting for more than half and another 30% in San Diego.

Just a couple dozen pounds of fentanyl were seized along the northern US border with Canada last year, CBP data shows, and experts say that the illicit networks in Canada are almost entirely separate from those in the US.

“We don’t get any significant amount of fentanyl from Canada,” Felbab-Brown said. “The small seizures that have been conducted at the northern border have mostly to do with US citizens buying fentanyl in Canada for personal consumption and then smuggling it themselves.”

Although law enforcement seizures of illicit fentanyl have surged in recent years, there’s also some evidence that the drug supply is changing again. The drug epidemic is dynamic, and the market can evolve quickly in response to different drivers of supply and demand, experts say – it’s been happening for decades.

According to the CDC, the first wave of the opioid overdose epidemic started in the 1990s with the abuse of prescription opioids. Purdue Pharma and its owners, members of the Sackler family, reached a multibillion-dollar settlement this year to resolve thousands of lawsuits alleging that the pain medication OxyContin caused a widespread opioid addiction crisis in the US.

There were rapid increases in overdoses involving heroin starting in 2010, which the CDC considers the second wave, but synthetic opioids – primarily fentanyl – took over around 2013.

Overdoses surged during the Covid-19 pandemic, reaching a peak between the fall of 2022 and the summer of 2023, when the CDC estimates that there were nearly 115,000 overdose deaths in one year. Synthetic opioids, primarily fentanyl, were involved in about two-thirds of those deaths.

But overdose deaths started a rapid decline at the start of last year. Fentanyl is still involved in most cases, but the latest data shows that annual deaths are down 22% compared with a year earlier. There were about 58,000 deaths involving synthetic opioids in the 12-month period ending in August.

Some experts suggest that a “fourth wave” of the opioid epidemic is underway, in which illicit fentanyl is more frequently mixed with other drugs, and the combination of fentanyl and stimulants can be particularly dangerous. During the time that overdose deaths involving opioids declined, those involving cocaine and psychostimulants such as methamphetamine increased, according to the preliminary data from the CDC.

Experts say that it’s difficult to attribute the rapid decrease in overdose deaths to one factor. Instead, it’s probably the result of a wide range of persistent efforts starting to make an impact.

Changes to supply started happening well before Trump’s tariffs were announced. In November, the US Drug Enforcement Administration said it was finding lethal doses of fentanyl in fewer pills than it did a year earlier. About 5 out of every 10 fentanyl pills that the agency tested last year had lethal doses of the synthetic opioid painkiller fentanyl, down from about 7 in 10 the year before, the agency said.

Drug samples analyzed by the Center for Forensic Science Research and Education also showed a slight downward trend in the average purity of fentanyl powder, but it was a relatively small dip in a highly variable drug supply.

Under President Joe Biden, the US Department of Health and Human Services launched a coordinated national strategy to prevent overdoses, with efforts focused on harm reduction – such as fentanyl test strips, overdose reversal medications and safe injection sites – as well as prevention, treatment and recovery from substance use disorder.

“Finally treating this like a public health condition after so many years of effort and attention may be starting to pay off,” Dr. Sarah Wakeman, senior medical director for substance use disorder at Mass General Brigham, told CNN in September.

In a deep dive into the trends, street drug scientist Nabarun Dasgupta and colleagues at the University of North Carolina found that non-fatal overdoses have also fallen significantly and that trends are relatively consistent at the state level – all signs that help experts feel that the overall trend is solid.