The parents of a teenager who died after being prescribed an anti-psychotic drug say his death was caused by "ignorance and arrogance" of medics.
A new independent review found Oliver McGowan's death at Southmead Hospital, Bristol, was "potentially avoidable".
His parents Paula and Tom McGowan said they repeatedly told doctors he should not be given the drug and have called for a new inquest to be held.
North Bristol NHS Trust said staff who cared for Oliver "did their very best" and that it would act on the findings.
Oliver, who was mildly autistic and had epilepsy and learning difficulties, was being treated for a seizure in 2016 when he was given olanzapine to sedate him.
The 18-year-old from Bristol died in intensive care 17 days later after a rare side effect caused his brain to swell.
The learning disability mortality review (LeDeR) into the death said that if Oliver had been assessed correctly on admission to hospital and staff had read his hospital passport, he may never have needed to be intubated and sedated.
It said: "There was a general lack of understanding and acknowledgement of Oliver's autism and how he presented himself when in seizure.
"Despite there being a body of written evidence - alongside verbal requests from Oliver and his family - not to prescribe olanzapine, there was no substantial evidence to illustrate that consideration had been given to explore alternatives to anti-psychotic medication."
Oliver's parents said they "had always known his death was avoidable".
"It is our opinion that Oliver died as the result of ignorance and arrogance of doctors who were treating him. Doctors who absolutely refused to listen to Oliver's direct instructions and to us," said Ms McGowan.
An inquest in 2018 ruled that the use of olanzapine was appropriate but the McGowans have now called for a fresh inquest, saying the first was "deeply flawed".
Fiona Richie, OBE, Chair of the Independent Review, said: "We hope the completion of Oliver's LeDeR and the wider recommendations for national change to the LeDeR programme, will be a part of Oliver's legacy and drive the change that is so urgently needed to prevent future deaths."
North Bristol NHS Trust Chief Executive Andrea Young said: "The staff who cared for Oliver did their very best in managing his complex needs.
"We are determined to offer exceptional care for individuals with learning disabilities and autism and we have significantly improved training and support for staff."