A doctor has admitted accidentally prescribing a Bristol woman with a massive overdose of a cancer drug, causing complications leading to her death.

Dr Jacqueline James told an inquest that Anna McKenna, of Knowle, had been given four times the amount of a chemotherapy drug needed to treat her bone marrow cancer.

Yesterday the Frenchay Hospital consultant told Flax Bourton Coroners' Court that she was sorry for the mistake.

And a jury was told that the hospital pharmacist who could have picked up the mistake could not be identified because the original prescription had disappeared.

Mrs McKenna, a mother-of-five, was diagnosed with cancer in March 2006, and was put on a four-day course of the chemotherapy drug Idarubicin.

But instead of being given 60mg of the drug over the four days, the 56-year-old was given 60mg on each of the four days.

The massive overdose left the housewife in terrible pain, with vomiting and diarrhoea.

Tests at the Bristol Royal Infirmary found the treatment had left her with almost no white blood cells left in her blood, leaving her immune system severely lowered.

Mrs McKenna developed complications, including fever and renal failure, and died at the Bristol Oncology Centre on April 18, 2006, three weeks after she started her first session of chemotherapy. Her husband, retired engineer David, and other members of her family were in court yesterday to hear Dr James make her apology.

Speaking about the moment she noticed her mistake, Dr James said: "I saw in my own notes that I had put in the dose of Idarubicin incorrectly.

"The records showed that she had been given four times the required dose. I am very sorry that a mistake was made."

But Dr James's error was not the only factor that led to Mrs McKenna's death, the jury heard.

Staff in the pharmacy at Frenchay Hospital who could have picked up on the oversight also misinterpreted the dosage.

The inquest was told that any questions about the detail of the prescription should have been referred back to the doctor who made it out. But the pharmacist who should have checked it failed to screen the prescription properly or notice that the dosage appeared to be wrong.

Crucially, the prescription which could have identified that pharmacist has gone missing, and no one knows who it was.

The jury of six women and four men at Flax Bourton Coroners' Court heard that Mrs McKenna, who was originally from Hungary, was found to have a curvature of the spine in 2005.

In March 2006 she was diagnosed with multiple myeloma, a cancer of the bone marrow.

Doctors gave her two years to live, but the treatment that could have prolonged her life instead killed her.

A statement from pathologist Dr Hugh White, who carried out the post mortem, said: "On March 16 she was treated with Z-Dex (the chemotherapy drug), but instead of being given 15mg over four days she was given four times this on each of the four days. Records show she had a normal white blood cell count, but following the chemotherapy she had vomiting, diarrhoea and pain.

"In the BRI she had almost no white blood cells in her blood because of the treatment.

"She made a mild recovery, but developed fever, diarrhoea and renal failure, and died."

The information was given to police, who conducted their own investigation into Mrs McKenna's death.

But Mrs McKenna's over-prescription was not the only one at Frenchay, the court heard.

Shortly after the error that led to her death, another patient was given an overdose, made possible because of the way that drugs were dispensed from the pharmacy at the hospital.

Hospital trusts across the region have now changed their practices to ensure the same mistake does not happen again, the jury was told.

The inquest continues.

Tributes to Anna McKenna can be left at Lasting Tribute.