Failures to check medication at a pharmacy in Frenchay Hospital were partly to blame for a Bristol patient being given a fatal overdose of a cancer drug, an inquest heard.

Anna McKenna, from Knowle, died in April 2006 after she was given four times the chemotherapy drug she needed to treat her bone marrow cancer.

The inquest jury heard that since then the trust in charge of the hospital had changed its procedures to prevent a similar incident happening again.

Jurors were also told that Mrs McKenna's family had raised concerns about an overdose before doctors considered the possibility.

Consultant haematologist Dr Jacqueline James has already told the inquest jury she accidentally prescribed four times the correct amount of medication for the 56-year-old.

Mrs McKenna, a mother of five, was given 60mg of the drug each day for four days, rather than 60mg over four days in March 2006.

The mistake destroyed most of her white blood cells, leaving the housewife open to infection and in terrible pain, and eventually led to her death.

Yesterday the spotlight fell on how that prescription was dealt with by pharmacists.

Hospital bosses explained that major changes had been introduced in light of Mrs McKenna's death.

Flax Bourton Coroners' Court heard there had been a series of errors made by the team of pharmacists who dispensed the Idarubicin drug for Mrs McKenna's four-day chemotherapy treatment.

A jury was told they failed to confirm the prescription with Dr James, and they did not correctly check it against a protocol that advises on levels of chemotherapy drugs.

The pharmacist responsible for the checks is not known, and the prescription, which would identify that person but which staff failed to photocopy, was also lost.

But mistakes with prescribing Idarubicin were not confined to Mrs McKenna's case.

The inquest heard that at the time of her death there were three similar incidents of Idarubicin overdoses across the country.

Up to one in 10 of all prescriptions from Frenchay Hospital also had to be re-checked with doctors before they could be dispensed.

In April 2006, immediately after Mrs McKenna's death, changes were introduced to prevent mistakes similar to those that led to her overdose.

Andrew Davies, who joined North Bristol NHS Trust as director of pharmacy in July 2007, said there were now two pharmacists to screen chemotherapy prescriptions.

The prescription protocol, detailing treatment dosages, has also been made clearer and is available online for pharmacists to check before dispensing each prescription.

Mr Davies said: "In the course of Mrs McKenna's treatment she was prescribed an excess of Idarubicin.

"The prescription cannot be located, but it is clear that an error was made."

Dr Jennifer Bird, a consultant haematologist who dealt with Mrs McKenna and helped devise the new protocol, added: "The protocol has now been changed. The way the dose is written has been altered in response to what happened to Mrs McKenna. This is not to say the protocol in 2005 was wrong or misleading, it is just to make it clearer."

The inquest also heard that Mrs McKenna's family were worried about her lack of recovery after she was admitted to the Bristol Oncology Centre following her botched chemotherapy.

Matthew Barnes, representing the McKenna family, told the court they repeatedly raised serious concerns over a possible overdose, but they were not considered by doctors until three weeks after her chemotherapy.

Dr Bird, who oversaw Mrs McKenna's treatment at the Bristol Oncology Centre, said the information never reached her, possibly because she was on annual leave.

She said: "If that had been reported to me it would have caused extreme concern and we would have wanted to know on what basis they felt that. I would have investigated as soon as possible and as thoroughly as possible."

A letter from Dr James to staff at the hospital outlined what should have been prescribed, but not what was actually prescribed, delaying any investigation into a possible overdose.

But even if doctors had known it would have made no difference, as the damage was irreversible, the inquest heard.

Dr Bird said: "Although we were unaware of any possible overdose, the treatment would have been identical and in my opinion the outcome the same.

"There was no specific rescue therapy to reverse the effects of the excessive dose."

The inquest continues.