A mother of five died after a consultant mistakenly prescribed a lethal dose of a chemotherapy drug, an inquest heard.
Anna McKenna was given four times the recommended daily amount of Idarubicin to treat her bone marrow cancer.
The overdose destroyed almost all of the 56-year-old's infection-fighting white blood cells, leaving her immune system powerless against disease.
Her kidneys failed and she died three weeks after first taking the drug. Her doctor admitted prescribing 60mg of the drug per day instead of 15mg.
'I am very sorry that a mistake was made,' Dr Jacqueline James, a consultant haematologist at Frenchay Hospital in Bristol, told the inquest.
'She was given four times the required dose. I had written out the prescription after a long and emotional meeting with Mrs McKenna and her family and filled it out wrong.' Mrs McKenna, a housewife from Knowle in Bristol, was diagnosed with multiple myeloma in March 2006.
The chemotherapy drug was prescribed to prolong her life but she died of renal failure in April 2006.
Dr James' error was not picked up by staff at the hospital's pharmacy. The prescription, which would identify the pharmacist at fault, has gone missing.
The inquest continues at Flax Bourton Coroner's Court.