He didn't know that it contained the powerful opioid painkiller fentanyl, a few milligrammes of which can be lethal.
Joseph died of an overdose later that evening in December 2016.
He'd already taken an antianxiety medication earlier on and the cocktail of drugs killed him.
Such tragedies have become commonplace in the United States, where, according to the government, fentanyl and other synthetic, or man-made, opioids killed 32,000 people in 2018.
Until now, Europe has managed to avoid a crisis of this scale, but police and experts warn that the continent could yet be hit.
More fentanyl is on the market and is leading to surges in overdose deaths in some countries.
"Outside of really specific circumstances, such as people in the final stages of cancer, taking fentanyl is worse than playing Russian roulette," Joseph's mother, Juliette Boudre, said.
Her son first became addicted to tranquilizers, before gradually turning to painkillers such as codeine.
"The disturbing thing about fentanyl is the profile of consumers," Les Fiander, head of Europol's drugs team, said.
"The consumers are quite young and they don't know what they're taking, because fentanyl is often mixed with other drugs, with heroine, with cocaine.
"That represents a big potential danger for individuals who have no tolerance to opioids," he said.
Months earlier, music icon Prince had also died, aged 57, after an accidental overdose involving fentanyl.
His death symbolises the devastation wreaked by the substance which in the US has become a veritable serial killer.
The drug is available on prescription as a pain relief patch, a nasal spray or a pill to dissolve under the tongue.
Many patients overdose after misusing prescribed fentanyl, or after buying fentanyl or other opioids under the counter.
Fifty times stronger than heroin and up to 100 times more potent than morphine, the opioid is also produced illegally, mostly in China and Mexico.
It can be ordered on the dark net, arriving through the post in the form of powder or tablets.
The yellowish substance is then smoked, sniffed, injected or transformed into a tablet.
Fentanyl can be lethal from as little as two milligrammes, equivalent to a few grains of sand.
But traffickers and users are rarely capable of measuring quantities so precisely.
The epidemic in the US was sparked by doctors, lured by some in the pharmaceutical industry, overprescribing opioid pain medication.
President Donald Trump declared the opioid crisis a "public health emergency" in October 2017.
The situation in Europe, however, is different, experts told AFP.
Doctors are careful not to overprescribe opioids such as fentanyl to patients who don't need them, Paul Griffiths, scientific director of the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA), said.
Nevertheless a number of opioids prescribed in Europe are beginning to cause concern, notably tramadol which can lead to dependency and overdoses when misused.
The crisis in the US has also made hard drug users in Europe wary, said Magali Martinez, a researcher for the French Monitoring Centre for Drugs and Drug Addiction (OFDT).
"Most of them consider fentanyl to be dangerous because of the high risk of overdosing."
But, she added, the drug is also perceived as "uninteresting", as "its effect is described as debilitating rather than euphoric".
Addiction to fentanyl in Europe is rare, but cases do exist.
Jacques, whose name has been changed for this story, became hooked on the opioid despite working in the health sector and being aware of the risk of addiction.
A regular cocaine user, the 50-year-old French man turned to the substance after his divorce and a motorbike accident that left him with several fractured bones.
It marked the beginning of a descent into hell, Jacques said.
The first few hits were satisfying, giving him the illusion of happiness and connection to other people.
But soon he began needing more, going from two to three sniffs a day, to a daily dose of five or six small spray bottles.
The symptoms gradually got worse.
Drowsiness at work, sweating fits, dizzy spells, nausea, constipation and sharp pain in the legs plagued his days.
He used his professional status and a few tricks to access the drug for five years.
Twice, Jacques overdosed. His friends saved him, but despite the close calls he couldn't stop himself.
"I was trapped. I couldn't get any pleasure out of it, only suffering.
"The last two years, every three days I would tell myself 'I quit'. But my whole life was focused on the next fix."
He hasn't touched fentanyl for 12 months now, which he credits to daily meetings at Narcotics Anonymous.
The EMCDDA does not have figures for deaths specifically related to fentanyl in Europe.
For 2017, it recorded 8,200 overdose deaths in the continent taking all types of drugs into account.
Of these, about 70 percent were linked to opioids, and out of those, the majority were attributed to heroin, Griffiths said.
But an overdose is rarely due to a single drug, and a lack of precise data could mean that the role of fentanyl and its multiple derivatives -- substances with very similar molecular structures -- is slipping under the radar, the EMCDDA says.
That's a fear shared by Joseph's mother.
At the time of his death, there was no investigation.
Fentanyl was only detected several weeks later when Boudre managed to get one of the pills that had been hidden by her son analysed, thanks to a friend in the police.
In Europe, seizures of the drug are on the rise.
Police intercepted more than 15 kilos (33 pounds) in 2017, compared to one kilo the year before.
That would be enough to make millions of doses, according to Griffiths.
Some European countries have seen spikes in overdose deaths.
Britain recorded 75 deaths related to fentanyl in 2017, a 29-percent increase from the previous year, officials say.
In Sweden, a report by the EMCDDA and Europol noted that fentanyl and its derivatives have caused at least 370 deaths since 2014, making it more lethal than heroin.
And a shortage of heroin in Estonia at the beginning of the 2000s saw fentanyl become the most used opioid among drug addicts, Griffiths said.
According to EMCDDA figures, there have been 1,600 overdose deaths in the small Baltic country since 2001, the majority due to fentanyl and other synthetic opioids.
"Last year they took out one criminal group and fentanyl almost disappeared" from the country, Griffiths added, saying both health sector and police efforts were beginning to pay off.
In France, the substance's impact remains limited, with fewer than 10 deaths a year directly linked to fentanyl, and seven deaths related to fentanyl derivatives and analogues, developed to imitate a drug, over the three years between 2015 and 2018, according to the OFDT's Martinez.
But 10 million people in France are prescribed opioids, which vary in strength, the French National Agency for Medicines and Health Products Safety said in a recent report.
"Caring for people in pain creates a permanent risk of a health crisis," said Matthieu Noel, head of strategic analysis at the French anti narcotics unit, Ofast.
Anti-drug units have dismantled small laboratories in Estonia, France, Germany, Poland, Slovakia and Sweden in the last few years.
But "most of this stuff comes from China, normally through the dark net, and it's brought to Europe by parcel post," said Europol's Les Fiander.
"It's quite an anonymous process… and it is very hard to detect."
The networks are "very sophisticated operations, organised like a pharmaceutical or commercial company, with people responsible for the logistics, orders and the website."
The European police agency doesn't "want to be alarmist", he added, but it is taking the threat seriously and is working closely with US authorities.
Thirty-four of the 49 new synthetic opioids detected in the last 10 years on the European market are derived from fentanyl.
Six appeared for the first time in 2018.
But the development of organised crime in Mexico is worrying Europol the most.
"Recently we've had Mexican criminals identified within Europe, actually involved in producing methamphetamines," Fiander said.
"Perhaps in the future they could switch to fentanyl. That would be a very serious situation."
For traffickers, fentanyl is a very profitable enterprise, said Griffiths, of the EU’s monitoring centre.
According to the US Drug Enforcement Administration, a kilo of illegal fentanyl can generate at least $1.5 million.
"Synthetic drugs will become more and more important as it becomes harder to find places in the world where you can grow coca and opium poppies," Griffiths said.
"There's a real market advantage in synthetic drugs that are highly potent and fentanyl fits very much in that model," he added.
The substance and its derivatives have already been found in fake Xanax pills and in some e-liquid cartridges for electronic cigarettes, according to Europol and EMCDDA.
Confronted with this multifaceted danger, EU health services want to facilitate access to an antidote in the case of an overdose, naloxone, formerly only available on prescription.
Almost a dozen EU countries have a programme to put ready-to-use kits on the market, which take the form of injections or nasal sprays and would not require first having seen a doctor.
But its availability in pharmacies isn't nearly sufficient, specialists say.
AFP /