Washington (AFP)

Donald Trump has decided to impose new customs duties on China, especially because it does not, he said, stopped sales of fentanyl to the United States, where this synthetic drug is wreaking havoc.

Here are the main elements of the debate:

- A very profitable drug ... -

Fentanyl is a synthetic opiate that, in its legal form, is used as a sedative in the treatment of severe pain, especially for cancer patients.

It may be diverted from its original use or sold illegally as a powder, spray or counterfeit tablets.

Traffickers also use it as additives to other substances, particularly heroin and cocaine, because it is much more profitable.

Fentanyl is cheaper to produce since it does not need poppy or coca fields. And small quantities are enough, since it is 50 times more powerful than heroin.

- ... and very deadly -

Fentanyl consumption has exploded since 2013 in the United States, fueled by the opioid crisis.

At first, the over-prescription of painkillers pushed many Americans to stronger drugs, including fentanyl.

Then, awareness of the problem led to lower prescriptions for painkillers, which sent dependent people to illegal markets, where fentanyl is cheaper than other products.

But its potency makes it particularly dangerous: according to the Drug Enforcement Administration (DEA), two milligrams of fentanyl can be a fatal dose.

And consumers do not always know that fentanyl has been used as an additive in the drugs they buy.

In 2018, the number of fatal overdoses fell for the first time in twenty years in the United States, but deaths from fentanyl and other synthetic opiates continued to increase, with 32,000 victims.

- China, first producer? -

When US authorities began to oversee the distribution of opiates, Chinese laboratories began mass-producing copies of fentanyl.

According to Mike Vigil, a former DEA international officer, China currently produces 85% of the world's fentanyl. Beijing believes these accusations unfounded.

In the US illegal markets, however, fentanyl is often sold under the names "China girl" or "China white".

Consumers can get them on the internet, from sites like Weiku.com, and can receive their parcels by mail, according to a report from the US Congress.

On April 1, under US pressure, China announced that it would list all types of fentanyl on its list of controlled substances, that it would strengthen its inspections, monitoring the internet and customs parcels. .

- Efforts doomed to failure? -

By slightly changing the composition, Chinese laboratories can continue to market problematic products and "it is very difficult to spot for regulators," says public health economist Roger Bate, who has just published an article on the subject.

"There are thousands, perhaps tens of thousands of small laboratories that Beijing does not know about," he said in an interview with AFP.

In addition, he says, if China agrees to block sales to the United States of websites such as Weiku.com, "sellers can still ship their products to other countries (...) where they can be repacked. "

- Other countries in the ranks -

"As we put pressure on China, the substances will simply be sent to Mexico so that (fentanyl) is manufactured there," a DEA official told AFP on condition of anonymity. .

The production could also "be supported by the Chinese diaspora in other Asian countries", such as Vietnam, notes Roger Bate. For him, India or Russia - which flooded Estonia with fentanyl from 2002 - are also able to produce it.

© 2019 AFP