A young man who died at a hospital on the NSW north coast three years ago was handcuffed, injected with sedatives and held face-down on a mattress before he stopped breathing, an inquest has been told.

Tristan Naudi, 23, was taken to Lismore Base Hospital on the evening of January 18, 2016, after he took lollies he believed to contain the drug LSD. He was later found to have ingested MDMA, also known as ecstasy.

Tristan Naudi, 23, died at Lismore Base Hospital in 2016.

On Monday, an inquest at the NSW Coroners Court was told the drug unexpectedly made his behaviour erratic, which was out of character, and he became a danger to his housemates and himself.

Police responded to Mr Naudi's home at Bangalow after triple zero calls, including one where he asked "can you help me". He was taken to hospital in the back of a caged police car and placed in a mental health isolation room.