But Mavis Eccleston survived the apparent suicide pact after relatives called at their Cannock home unexpectedly and discovered them both unconscious.
Her husband Dennis, 81, died the following day as she held his hand, Stafford Crown Court heard.
A 14-page note found at their Raven Close bungalow indicated that they had planned to take their own lives due to ill health and “harassment day in, day out”.
Police found part of the glazed front door blacked out with taped bin bags due most likely to “neighbourhood tensions”, said Mr Tony Badenoch, prosecuting.
The couple, who had been married for almost 60 years, had become housebound since Mr Eccleston, a retired groundsman, had been diagnosed with bowel cancer and was forced to give up driving.
The day they were found, February 19 last year, family visitors had not been expected, said Mr Badenoch.
But granddaughter Aimee Smith and her mother Lynne had called in and discovered Mr Eccleston apparently asleep in his armchair and his wife slumped on the floor.
At Stafford Hospital,sympathetic staff, aware of the circumstances, put them in adjoining beds. Dennis Eccleston had signed a “do not resuscitate” declaration so no attempts were made to revive him.
The jury heard that in the days after his death the defendant told mental health nurses that her nurses that her husband had not been aware she was administering a potentially lethal dose of drugs, leading to the charge of murder against her.
Later, Mrs Eccleston told police he had asked her to do it and she had been confused in the earlier interview.
She had been woken by a loud bang at 3am on the day of the overdoses and found Dennis collapsed on the bedroom floor.
“She said she could no longer see him in such pain,” said Me Badenoch.
The defence will argue that the overdose alone did not kill him and that if it did and a suicide pact could be proved then she would be guilty of the lesser charge of manslaughter.
“It is a tragic case for all concerned, including her and family members - nothing I say in presenting this case will be to suggest otherwise,” said Mr Badenoch.
But he went on: “The power to end, assist, encourage or even to agree to end life altogether does not extend to the ordinary citizen - in this case, that includes his wife of a lifetime, the defendant.”
The prosecution opening was held up for several minutes after Mrs Eccleston broke down in court and the proceedings continued in her absence.
She denies both murder and manslaughter.
The case continues.