A junior doctor and two nurses at the centre of a toxic drug error that caused two cancer patients to die from an overdose at a Birmingham hospital have refused to answer questions in the coroner’s court.

Dr Kiran Tawana and nurses Vongai Gondo and Catherine Kunatsa yesterday invoked Rule 22 of the Coroner’s Rules, which gives witnesses the right to decline to answer questions if they believe it may incriminate them in a court case.

But Birmingham coroner Aidan Cotter told the jury-of-seven they “should not draw any conclusion from that decision”.

The court has heard Dr Tawana told colleagues she made an error when writing prescriptions for patients Paul Richards, a 35-year-old IT consultant from Sutton Coldfield, and Baljut Singh Sunner, 36, from Stechford, which led to them being given five times the normal dose of fungal infection drug Amphotericin.

Confusion arose over the drug as the original “conventional” Amphotericin, branded Fungizone, is prescribed at around one milligram per kg of a patient’s weight. Yet modern forms branded Ambizone and Ambleset, have dosages of three and five milligrams per kg.

Dr Tawana prescribed five milligrams of ‘Amphotericin’, which nurses made up using Fungizone as it was routine practise on the ward to refer to the conventional form as Amphotericin and the others by brand name, the court heard.

Consultant Dr Prem Mahendra, chair of the West Midlands haematology training committee, who recruited Dr Tawana as a trainee haematologist said she had no doubt in the junior doctor’s clinical abilities.

“For 18 months, Dr Tawana has worked at Queen Elizabeth Hospital, in Edgbaston, she is outstanding,” said Dr Mahendra. “Before the deaths, there was no formal training about the drug Amphotericin. Trainees were told the gold standard for prescribing any drug was to use the generic name.

“Dr Tawana was only on the fifth day of her second rotation on Ward 19 and had done seven weeks there. I think given that time, it would have been difficult for her to know the running of that ward.”

Dr Mahendra added haematology doctors started ‘breaking the rule’ over using brand names for Amphotericin after 1994 when three new forms of the same drug emerged with different doses, but there was no region-wide protocol for new doctors.