An elderly doctor contributed to the deaths of three of his patients after giving them high doses of morphine, an inquest has heard.
And the County Durham coroner called on medical practices across the country to carry out reviews so that similar incidents do not occur.
Coroner Andrew Tweddle said he would be writing a number of recommendations to medical authorities.
The inquest heard that 75-year-old Dr Howard Martin had administered doses of morphine to Frank Moss, 59, Harry Gittins, 74, and Stanley Weldon, 74.
He was cleared of murder after a trial at Teesside Crown Court in December 2005.
All three men had been patients of Dr Martin when he was a partner at the Jubilee Medical Group, which had surgeries in Newton Aycliffe, Shildon and Eldon, all in County Durham.
Reading from a seven-page statement, Mr Tweddle said: "His patients would have expected treatment that was in line with the accepted medical practice of the day.
"I think it is appropriate for those who have power to influence the way GPs work and operate to consider once again what further changes are necessary, if any, in an endeavour to attempt to avoid similar fatalities in the future.
"Accordingly, I propose to write a letter to the relevant authorities, in general terms, urging them to review their systems once again, in the light of the evidence given at these inquests."