Katherine Jane Bailey, known as Kate, died at New Cross Hospital in Wolverhampton in the early hours of December 22, 2020.
She had a toxic level of an opioid painkiller in her system, the inquest heard.
Black Country area coroner Joanne Lees recorded an open verdict because it was impossible to establish for certain how she had taken such large quantities of the drug while in the hospital.
Mrs Bailey’s family now plans to sue the Royal Wolverhampton Trust, which runs New Cross, for clinical negligence.
Her husband Michael said: “My family and I are very grateful to the coroner for the thorough way she investigated the evidence, but we’re devastated that we still don’t have any answers about what happened to Kate.
“We feel we have no option now other than to pursue a clinical negligence claim to challenge the trust to look at the events which led up to her death, and whether anything further could have been done to prevent it.”
AssociateMichael Portman-Hann of FBC Manby Bowdler, who represented the family at the inquest, said: “We completely understand why the coroner returned an open verdict as, on the information available, she could not be sure how Kate ended up with a toxic level of the drug in her system.
“The trust has since changed some of its operating systems as a result of this case, but there were clearly things that went wrong during Kate’s time in the hospital which need to be investigated.”
The inquest heard that Mrs Bailey was admitted to an ear, nose and throat ward at New Cross on December 19 after having major nose bleeds, and she was suffering from anxiety and alcohol withdrawal. She died in the early hours of December 22 despite attempts at resuscitation.
The 56-year-old, from Signal Grove, Bloxwich, was initially given the painkiller on an as-needed basis, but on December 21 that changed to up to four doses at regular intervals during the day.
The hospital records show the specific times that Mrs Bailey was given the drug. She died at 1.30am the following morning.
The inquest was told that Mrs Bailey had been anxious during the day leading up to her death and had repeatedly asked to go outside for a cigarette, which she had done accompanied by a member of staff.
She had been seen by a doctor after apparently developing hallucinations and messaged her family to say her “head was all over the place”.
The coroner said she was recording an open verdict because she could not be certain where the medication had come from, how it had got into Mrs Bailey’s system or whether her death had come about because of some underlying condition which reacted badly with the drug.
Dr Brian McKaig, chief medical officer at The Royal Wolverhampton NHS Trust said: “As this is now a legal matter, the trust is currently unable to comment on specifics of the case. We have however fully complied with requests for information from the family’s solicitors.”