Dutch authorities are warning people against ordering prescription painkillers online after a 30-year-old man died in Amsterdam after taking counterfeit oxycodone.

The pills were bought online without a prescription, according to the Trimbos Institute, a Dutch scientific research agency.

They did not contain oxycodone – which is prescribed for patients with severe pain – but rather nitazenes, which are synthetic opioids that are much stronger than oxycodone, morphine, or fentanyl.

The drugs are so potent that only a few milligrams can cause fatal breathing problems, according to Trimbos. The effects also last longer, raising the risk of an overdose.

Police in Amsterdam are still trying to identify where the man who died got the fake oxycodone. But his death is one of several health crises tied to synthetic drugs in the Netherlands recently.

‘Dangerous to order prescription drugs online’

The Dutch Health and Youth Care Inspectorate (IGJ) said multiple people have received emergency medical care after taking pills that were sold online as oxycodone but turned out to contain nitazenes.

The drugs are sold online and on social media, the inspectorate said. They look like oxycodone and typically have original-looking packaging – making them “almost indistinguishable” from the real thing, it added.

“This shows how dangerous it is to order prescription drugs online,” IGJ chief inspector Henk de Groot said in a statement.

“It may look real, but you have absolutely no idea what you are buying”.

The warning comes amid an uptick in the availability of nitazenes and other synthetic opioids in parts of Europe, according to the European Union Drugs Agency, which described them as an “important emerging threat”.

Trimbos urged people to avoid buying pain medication online and said people should call for emergency help if they begin feeling unwell after taking oxycodone.

Meanwhile, IGJ said people can report websites selling prescription medicines to investigators.

“For drugs, go to your doctor and pharmacy,” de Groot said.