A 71-year-old Ulverstone man who died at the North West Regional Hospital in early 2020 was found to have died from an accidental drug overdose, and not from the condition named on his death certificate.
Coroner Simon Cooper said in his investigation that the man had been given 10-times the amount of drug that had been prescribed, with the overdose killing him.
The drug overdose only came to light after the death was referred to the Coroners Office.
Mr Cooper said three days after the man's death in January 2020, a medical practitioner signed a medical certificate of death saying the cause of death was metastatic mesothelioma (a type of cancer).
"A regular review of the certificate by the executive director of medical services of the NWRH identified an issue with the certificate and the Coroners Office was notified of the matter on 13 January 2020.
"The coronial investigation revealed that rather than being given 2 milligrams of hydromorphone in the NWRH (as he was prescribed), he was given 20 milligrams of that drug."
Mr Cooper strongly criticised the staff responsible for the drug overdose.
"While I am quite satisfied that the administration of 10-times the appropriate amount of hydromorphone was not deliberate, it bespeaks a shocking lack of attention to basic principles.
"I accept that the overdose which caused the death was accidental ... Nonetheless, it was an accident with immediate fatal consequences."
He said the NWRH needed to ensure that type of accident could never happen again.
Mr Cooper also berated the staff member who had signed the death certificate.
"On no reasonable view of the circumstances was it appropriate to issue a medical certificate of death."
A Tasmanian Health Service spokesman said the service extended its condolences to the family of the deceased man.
"The THS notes the Coroner's comment.
"The THS is committed to ensuring it always looks to perform and provide care to the highest level possible, which includes learning wherever possible.
"Accordingly, recommendations of an analysis of the incident have been implemented."