Retired mechanic David Goss, 68, of Newell Street in Limehouse, was found unwell in October.
But when the carer who raised the alarm told an ambulance worker Mr Goss’s regular medications included diabetes drug metformin, they misheard it as morphine.
Mr Goss also had “pin-prick pupils”, which can be caused by opioid painkillers – a coincidence which reinforced the misapprehension.
Senior coroner Graeme Irvine told an inquest at East London Coroner’s Court it had been “a dreadful mistake”.
When Mr Goss was admitted to Newham Hospital, it was as a case of suspected opioid overdose.
He was even administered an opioid antidote called naloxone, the court heard.
After his death almost three weeks later from pneumonia, a pathologist reviewed his recent medical history and recorded the incident which triggered the deadly chain of events as a drug overdose.
Professor Alan Bates relied on that history as the weeks between Mr Goss’s hospital admission and his death made conducting posthumous tests for opioids “pointless”.
But testifying on Thursday (June 26), he said he had altered his conclusions after hearing more evidence.
Mr Goss had been staying in Roxwell Road, Barking, while works were carried out at his home in Limehouse.
No opioids were found at the Barking property and GP records supplied after Mr Goss’s inquest was opened last November showed he had not been prescribed any opioids.
When Professor Bates asked to see test results from Mr Goss’s initial admission into hospital, they showed no evidence of opioids either.
Wheelchair-bound after a previous heart attack and stroke left him brain-damaged in 2005, two of Mr Goss’s three coronary arteries were more than 95 per cent blocked when inspected at autopsy.
He also had an enlarged, scarred heart and could have suffered a heart attack at any time – another potential cause of his shrunken pupils on the day he fell ill, said Professor Bates.
The pathologist accordingly changed his findings, saying Mr Goss’s obstructed arteries and heart disease were serious enough to have killed him without a drug overdose.
Senior coroner Graeme Irvine said he was “happy to accept” the revised cause of death, ruling Mr Goss had actually died from “complications of a long-standing health problem”.
Investigating the origins of the opioid “confusion”, the coroner reviewed London Ambulance Service records.
A paramedic had recorded: “Carer stated that Mr Goss self-administers morphine.”
“But you say that you never said that?” Mr Irvine asked carer Shahidul Rajon.
“No,” he replied from the witness box.
Mr Rajon told the court he had found Mr Goss suffering with “uncertain and abnormal” breathing and not responding to him as usual, so he called an ambulance.
He testified that he had worked with Mr Goss on a daily basis and his duties had included helping him take his medications, so he knew very clearly what they were.
“You are sure that you didn’t say to them that Mr Goss had been taking morphine?” Mr Irvine asked again.
“No sir,” said Mr Rajon, explaining that he had said metformin, not morphine.
“The most likely cause of this confusion is, in a very, very hurried, urgent set of circumstances, there has been down a breakdown in communication,” said Mr Irvine.
“It seems to me that this has been a dreadful mistake and I’m very grateful for you clarifying the situation. You have been very helpful.”
Describing Mr Rajon as “clearly spoken” and “intelligent”, the coroner said it was clear the carer had said metformin to paramedics, but “they have heard that as morphine”.
He ruled Mr Goss’s death as having been from natural causes.
“Had that cause of death been known back in November, I wouldn’t have opened the inquest,” he told Mr Goss’s sister.
“Can I offer you my sincere condolences? I’m so sorry for your loss. I’m sorry that it’s taken so long to get a straight answer for you.”
