Explainer: What is fentanyl, the 'deadliest ever drug' in crosshairs of Trump's tariffs on Canada, Mexico

And so begins another one of America's wars against drugs.

US President Donald Trump yesterday ordered 25% tariffs on Canadian and Mexican imports – lumping a 10% tax rate on goods from China as well saying Beijing needed to stanch the flow of fentanyl, a deadly opioid, into the United States.

In a statement issued by the White House, Trump said he has found "sustained influx of illicit opioids and other drugs has profound consequences on our Nation, endangering lives and putting a severe strain on our healthcare system, public services, and communities.

"This challenge threatens the fabric of our society.  Gang members, smugglers, human traffickers, and illicit drugs of all kinds have poured across our borders and into our communities," he said.

"Canada has played a central role in these challenges, including by failing to devote sufficient attention and resources or meaningfully coordinate with United States law enforcement partners to effectively stem the tide of illicit drugs."

Both Mexico and Canada have said they were preparing similar tariffs on US goods, while China added it would take "necessary countermeasures to defend its legitimate rights and interests".

China, meanwhile, has said the drug crisis was "America's problem" not a trade issue.

China denounces Trump tariff: 'Fentanyl is America's problem'

Taking to his social media platform Truth Social, Trump wrote, "This was done through the International Emergency Economic Powers Act [IEEPA] because of the major threat of illegal aliens and deadly drugs killing our Citizens, including fentanyl."

So what is fentanyl?

It is said to be the deadliest drug crisis in US history.

More than 100,000 Americans died from drug overdoses between August 2021 and August 2022 alone, according to Foreign Affairs

Fentanyl is a powerful synthetic opioid that is used medically to treat severe pain, often in patients who are recovering from surgery or those with chronic pain, like cancer patients.

It works by binding to the brain's opioid receptors, reducing the perception of pain. It is many times stronger than morphine, which makes it very effective for pain relief, but also dangerous if misused.

Fentanyl is sometimes prescribed in the form of patches, lozenges, or injections, but it has also become a major contributor to the opioid crisis due to its illegal production and distribution.

Illegally made fentanyl is often mixed with other drugs like heroin or cocaine, which greatly increases the risk of overdose, as it can be fatal even in small amounts.

Fentanyl is not a new drug, so why overdose deaths are reaching record levels now needs to be asked.

According to experts, the answer lies in a broader timeline that dates back to the late 1990s, marking the beginning of what the CDC identifies as the three waves of the opioid overdose crisis.

The first wave emerged with the widespread use of prescription opioids like OxyContin.

Around 2010, the second wave began when these medications became more difficult to obtain and increasingly expensive, prompting many opioid users to turn to heroin as a cheaper alternative with similar effects.

Today, we are experiencing the third wave, in which fentanyl has largely replaced heroin. While the exact reasons behind this shift are still being studied, one widely accepted explanation is that illicit fentanyl has become significantly cheaper to produce than heroin in recent years.

How the pandemic changed drug spread

The shifting pattern of opioid-related deaths suggests a notable change during the pandemic.

Prior to the COVID-19 crisis, the sharp rise in fentanyl-related overdose deaths in the U.S. was concentrated primarily in the eastern half of the country, with urban centers such as Washington, D.C., Baltimore, Philadelphia, and New York City being especially affected.

One possible explanation for this is that heroin in the eastern U.S. has traditionally been available in powder form, making it easier to mix with fentanyl compared to the black tar heroin more common in the western states.

The pandemic led to reduced cross-border movement, making drug trafficking more difficult. With bulkier drugs harder to smuggle, traffickers increasingly turned to fentanyl, which is far more potent and easier to transport in small quantities, including in pill form. This shift likely contributed to fentanyl spreading to regions that had previously been less affected by its impact.

Additionally, individuals seeking prescription opioids instead of heroin have faced growing risks due to the rise in counterfeit pills laced with fentanyl. This trend has been linked to an increase in overdose deaths reported by public health officials in cities like Seattle.

Another contributing factor to the rising fatalities is the pandemic's disruption of in-person addiction treatment, making it more difficult for those struggling with opioid dependence to access the care they need.

Fentanyl is 100 times more powerful than morphine and 50 times more powerful than heroin, according to the Drug Enforcement Administration.

Notable deaths

Rapper Coolio died from the effects of a fentanyl overdose, a US coroner has ruled.

Rich Homie Quan was also killed by the combined toxic effects of fentanyl, alprazolam, codeine and promethazine, according to a Georgia medical examiner.

Actor Angus Cloud died of an overdose of cocaine, methamphetamine and fentanyl