Raymond Stott was allergic to the antibiotic he was administered in error and died despite attempts by staff at St James’s Hospital to save him.
His daughter Jackie said: “When we found out it was not natural, we were absolutely devastated.
“We are so upset that a mistake has happened and it has taken our father. He was getting better, but he was taken through an error.”
The 66-year-old was admitted to hospital in March after collapsing at his home in Beeston, Leeds, with a heart attack.
He had a second one in hospital and was taken to the Intensive Care Unit, where he stayed for 21 days before being moved to a ward.
Mr Stott, who had 15 grandchildren, had been diagnosed with emphysema and had a tracheostomy to help him breathe, but was trying to communicate with his family.
He was due to have the tube removed on April 4, but early that morning his children Jackie, Jennipher, Brian and Christopher were summoned to the hospital urgently. Sadly they were too late.
Soon afterwards, they were told that a staff member had mistakenly given their dad the antibiotic amoxicillin, which was meant for another patient - but which Mr Stott was allergic to.
An antidote was given but the retired plasterer could not be saved. His death certificate lists “anaphylactic reaction to amoxicillin” as one of the causes of death.
“It still hasn’t sunk in that my dad has gone,” added Miss Stott, who lives in Barnsley.
“It if had been natural, we could say that he couldn’t go on any more. But he was fighting.”
She said the family were upset that they had no further contact from Leeds Teaching Hospitals NHS Trust until after the Yorkshire Post got involved.
“We felt he had been forgotten and his death had not been acknowledged.
“He was a lovely person, very kind and everyone used to call him Uncle Ray. He was a giver and he had lots of friends. There were 300 people at his funeral.”
Mr Stott’s death is being investigated by the Coroner ahead of an inquest.
Dr Yvette Oade, chief medical officer for Leeds Teaching Hospitals, said: “I’d like to express my sincere condolences and apologies to Raymond’s family.
“We are undertaking our own internal investigation to help identify the cause, review our processes and share learning to prevent anything like this from happening in the future,” she said.
“We will keep in contact with Raymond’s family to discuss the progress of our investigation, the findings when it is completed and to answer any questions they may have.”