A new junior doctor at a Birmingham cancer ward admitted making a mistake over the dose of a toxic drug after two patients died on her watch, an inquest was told.

Dr Kiran Tiwana, who was on her first week at Heartlands Hospital’s oncology ward, confided in a colleague over her prescription, that led to two cancer patients being given five times the normal dose of fungal infection drug Amphotericin. But an expert in drug safety told Birmingham coroner’s court the fatal overdoses of father-of-three Paul Richards, aged 35, from Sutton Coldfield, and Baljit Singh Sunner, 36, from Stechford, on Ward 19 at Heartlands were a “disaster waiting to happen”.

A jury of seven has heard confusion was caused over Amphotericin having various forms and doses.

The original “conventional” Amphotericin, branded as Fungizone, is prescribed at around one milligram per kg of a patient’s weight, while modern forms are branded as Ambizone and Ambleset, with dosages of three milligrams per kg and five milligrams per kg.

Dr Catherine Nicole, a specialist haematology registrar, said following the deaths in July 2007, Dr Tiwana, a Birmingham University graduate, revealed the error.

“Dr Tiwana said she may have prescribed the wrong amount,” said Dr Nicole. “She thought she had prescribed five milligrams of Amphotericin. We looked at the drug charts and it was apparent an error had been made.”

Consultant Dr Richard Lovell conceded that a new doctor would not know that writing Amphotericin, the generic name she had been taught to use as a medical student, would be interpreted by nurses and doctors on the ward as the conventional form.

He admitted it was easy to see how the mistake could happen as there was not a good system in place to prevent confusion and an accident from happening.

Prof Robin Ferner, an international expert in adverse drug reactions from City Hospital and a pharmacology professor at Birmingham University, said that the two patients were the first reported deaths in the UK from Amphotericin and until the tragedies, the drug had not been considered dangerous.

“This was a disaster waiting to happen,” said Prof Ferner. “Until this, I was not aware people could die from Amphotericin. Since these deaths, I have taught my students to always prescribe drugs by the generic name and check everything in their dosage manual, the British National Formulary (BNF).”

The National Patient Safety Agency has also issued guidance on the drug. Over the past three and a half years, there have been 53 reports of Amphotericin overdoses to the Agency but of these, only Mr Richards and Mr Sunner had died.