A terminally ill patient could have died from an alleged overdose given by an out-of-hours GP, a disciplinary hearing was told today.

Dr Michael Stevenson, 57, created a "small risk" of fatal consequences when he gave twice the recommended amount of a painkilling drug, an expert GP for the General Medical Council (GMC) claimed.

The locum doctor for the Cuedoc out-of-hours service visited the 84-year-old man in a Cumbrian nursing home who was in agony from gangrene.

He gave the patient 10mg intravenous objections of diamorphine and midazolam but a GMC Fitness to Practise panel was told that the latter dosage was too large.

Dr Christopher Robinson said the dose was "much higher" than the recommended norm.

Dr Robinson said: "Giving all that dose at once in combination with diamorphine is too large.

"It was too high and that can cause respiratory depression."

Asked by GMC counsel Suzanne Goddard QC if it could be fatal, he replied: "I suggest there was a small risk."

Dr Stevenson's instructions to nursing home staff to then administer 90mg of diamorphine via a syringe over a 24-hour period was also excessive because it did not take into account the patient was already using a morphine patch, Dr Robinson said.

A district nurse later voiced concern about the amount prescribed and reduced the diamorphine level to 60mg.

The patient later became more comfortable before dying three days later in December 2004.

Christina Lambert QC, representing Dr Stevenson, of Bootle, near Millom, told the panel that the expert had used guideline dosing figures from the British National Formulary. However, most palliative care specialists, such as Dr Stevenson, would use an alternative Palliative Care Formulary as that was specific to the field.

She added the panel may hear evidence in due course that the dose of midazolam was appropriate in line with recommendations from the Palliative Care Formulary.

The man's family was also deeply distressed about the inadequacy of the pain relief given previously, she said. Indeed, the patient's niece was begging for the nursing staff to help.

She said the morphine patch should not be "put into the mix" because it had demonstrated to be wholly insufficient for the man's pain and therefore Dr Stevenson gave the appropriate dosage.

Dr Stevenson, who also worked as a GP at the Health Centre Practice in Seascale at the time, also faces a misconduct charge over an out-of-hours visit he made to another terminally ill patient in September 2002.

Dr Robinson said in his opinion the GP had administered twice the amount of the painkilling drug - cyclimorph - that was needed for the 78-year male cancer sufferer. The patient died the following day.

In both cases, the expert witness said Dr Stevenson's overall treatment was "moderately below standard".

Yesterday, the panel, sitting in Manchester, was told a 59-year-old builder stopped breathing and went blue in the face moments after he was given diamorphine by Dr Stevenson on a home visit.

The doctor admitted mistakenly injecting six times the correct dose of diamorphine to alleviate the man's back pain. He suffered respiratory arrest but made a full recovery after paremedics arrived swiftly with an antidote.

The incident happened within a hour of Dr Stevenson visiting Workington grandmother Marjorie Wright, who he killed with an identical overdose.

He was sentenced to 15 months in jail in April 2007, suspended for two years, for the manslaughter of Mrs Wright, 58, who died in January 2005 after she had called Cuedoc with a migraine complaint.

The circumstances surrounding Mrs Wright's death do not form any of the misconduct charges that Dr Stevenson faces in the present inquiry.

He denies his fitness to practise is impaired because of his alleged misconduct.

The hearing continues tomorrow.