A terminally ill cancer patient was given a dose of a chemotherapy drug that was five times stronger than prescribed, an inquest has heard.
Barbara Curtis, 81, was being treated for acute myeloid leukaemia when the mistake was made by a pharmacy at Royal Bournemouth Hospital in December 2017.
She died less than three weeks later on 17 January 2018.
Both the cancer and the drug contributed to her death from sepsis, Bournemouth Coroner's Court was told.
The court heard Mrs Curtis was being given palliative care to help her to continue living at home, and was put on a course of cytarabine.
However, a mistake in the hospital pharmacy meant she was taking doses of 100mg of the drug, twice a day, rather than the prescribed 20mg.
Pharmacy technician Katherine Kendall told the hearing she had inadvertently selected the wrong vial of the drug containing a higher concentration and incorrectly amended the paperwork
"I hadn't been paying the proper attention," she said. "At the time I thought I was doing the right thing."
She added that it was a "busy work environment" and it was "possible that contributed to what I did".
The court heard Ms Kendall's amendment was checked by two other members of the pharmacy team who did not spot the error.
Dr Renata Walewska, a haematology consultant who was treating Mrs Curtis, said she was "horrified" when the mistake was brought to her attention and alerted the patient and her family.
She said the treatment, which Mrs Curtis had been receiving for four and a half days, was immediately stopped on 3 January 2018.
She said Mrs Curtis had not displayed any side-effects at that stage but was suffering with an infection, which later deteriorated and she died in hospital.
Pathologist Dr Stephen Holwill said her cause of death was neutropenic sepsis due to acute myeloid leukaemia treated with cytarabine.
He said the leukaemia was "on the balance of probabilities the greater cause of death" but the cytarabine would have made a "more than trivial contribution".
Expert witness Dr Lisa Lowry, a consultant haematologist, said Mrs Curtis was prescribed a small dose of the drug and 100mg was given to other patients receiving more intensive treatment.
"This turn of events would not have been unexpected with the correct dose," she added.
The inquest continues.