Dr Cox, 47, a rheumatologist at the Royal Hampshire County Hospital, said afterwards that he was devastated by the verdict and the sentence.
But, speaking publicly for the first time since his arrest a year ago, Dr Cox said that the injection had been 'a bona fide act that was solely in the interest' of Lillian Boyes, 70, whom he described as 'a brave and patient lady'. He added: 'It seems somewhat harsh to criminalise me for doing my best in what were quite exceptional circumstances.'
Dr Cox described the past year as 'very harrowing' and said that he hoped to resume a normal life as quickly as possible. But his employer, Wessex Health Authority, said he would remain suspended on full pay until the General Medical Council, the doctors' disciplinary body, reviews his case.
Later, a spokeswoman for the GMC said it was unlikely that any hearing could take place within six months, the first opportunity at which the professional conduct committee to make a decision. Its options range from taking no action to striking his name from the register if it found evidence of 'serious professional misconduct', though some believe the committee may be lenient.
Dr Cox was found guilty on Saturday of attempting to murder Mrs Boyes by giving her a lethal injection of potassium chloride in August 1991. Mrs Boyes, who was terminally ill with acute rheumatoid arthritis and in agonising pain, had asked him to help her die.
Mr Justice Ognall, sentencing Dr Cox yesterday, told him that the trial had been a testing and melancholy experience. 'I have no doubt that for you it has been a terrible ordeal and the verdict a personal and professional catastrophe,' he said.
Dr Cox had, however, been convicted on the most clear and compelling evidence, the judge said. 'What you did was not only criminal, it was a total betrayal of your unequivocal duty as a physician.'
Such conduct, Mr Justice Ognall said, could never be legally excused.
He appreciated, however, that Dr Cox had allowed his professional duty to be overridden by compassion for a dying patient who had become an admired and cherished friend. He said that the sentence reflected the 'wholly exceptional, if not unique' nature of the case as well as the seriousness of the crime.
Two leading rheumatologists who were witnesses for the defence, Professor David Blake and Dr David Scott, afterwards condemned what they called an 'obscene sentence'. They said that although the trial had not been about such issues, it was probable that the judge had inadvertently advanced the cause of euthanasia.
Mrs Boyes's two sons, Patrick and John, who attended the trial, said in a statement yesterday that they were extremely saddened by the verdict.
'We both feel that Dr Cox is an excellent doctor and that he looked afer our mother with care and compassion at all times,' they said. 'Mother was a very special and caring person and we are certain that she would be horrified that her passing has resulted in this trial and the conviction of a doctor whom she respected and considered a friend.'
Dr Cox's counsel, Sydney Kentridge QC, had asked the judge to give him an absolute discharge, arguing that he had acted from selfless motives in an unprecedented situation and had already been punished enough.
Dr Cox, he said, was not only a skilful and dedicated doctor, but a leading specialist in the rheumatology field who conducted important research into improving patient care.
Mr Kentridge said that if doctors needed any reminder about the legal limits on their activities, the judge in his summing up had given 'clearer guidance to the medical profession than any previous judgment in a court in this country'.
The case is a landmark since Dr Cox is the first clinician to have been convicted, though several others in recent years have walked free from court. Thomas Lodwig was charged with the murder of Roy Spratley, 48, whom he injected with a cocktail of drugs - potassium chloride and lignocaine - which brought about his death within minutes. The Crown Prosecution Service dropped the charges during the trial at the Old Bailey in March 1990 after cancer research specialists gave evidence that the two drugs had been used to relieve pain with 'encouraging' results.
Another physician, Dr John Carr, was cleared of attempted murder after a two-week trial at Leeds Crown Court in November 1986. The jury was told by a pathologist that the patient, Ronald Mawson, 63, might have died from the effects of lung cancer rather than the injection of phenobarbitone which Dr Carr had used to ease his pain.