A 57-year-old Oswaldtwistle man suffered a brain haemorrhage while he was being treated in hospital for blood circulation problems.
An inquest heard that David Forrest was undergoing a process known as thrombolitis which involved an infusion to break down blood clots in his leg.
It also required an injection of heparin to prevent further blood clotting.
But during the treatment he complained to his wife that it was "too strong" and asked her to get the machine turned off.
Mr Forrest, a painter and decorator, of Edinburgh Drive, had a history of circulation problems in his leg which was due to narrowing of the arteries due to smoking.
He had undergone several by-pass operations previously.
Home office pathologist Dr William Lawler said there had been a large haemorrhage within the brain and there were two parts to it.
One haemorrhage was several days old and the other more recent.
Recording a verdict of misadventure coroner Michael Singleton said cerebral bleeding was a recognised but rare complication of the procedure carried out quite properly by hospital staff.
"Of the options available this was the one that was seen as the best," said Mr Singleton.
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