The Dutch health ministry and addiction clinic Trimbos have issued a warning about a life-threatening fake version of the drug oxycodone which may have already killed one user in the Netherlands.

The fake pills contain a different chemical –  isotonitazepyne – a synthetic opioid which, according to some research, is 1,000 times more potent than morphine.

The person who died last Friday may taken the fake drug, having bought the pills online without a prescription, although the cause of death has not yet been confirmed, the Trimbos institute told Dutch News. The pills were found close to the body of the 30-year-old man in Amsterdam.

Oxycodone is a highly addictive painkiller used in the Netherlands by cancer patients and as part of palliative care.

Isotonitazepyne and other nitazenes “work for longer than other strong synthetic opioids and that increases the risk of overdosing,” Trimbos said. “A couple of milligrammes can cause serious health risks such as breathing difficulties, which in turn can lead to death.”

Another version of the drug, protonitazene, was found earlier by researchers for the Dutch Drugs Information and Monitoring System in fake oxycodone pills which had been bought online.

Chief health inspector Henk de Groot said the incident “shows how dangerous it is to buy pills which require a prescription online.”

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