Very few doctors in New Zealand are disciplined for inappropriately prescribing drugs.
There were only 25 cases involving 24 different doctors between 1997 and 2016, researchers at the University of Auckland have found.
And when doctors were caught, it usually meant the end of their career.
Author Katharine Wallis says although rare, when it does happen there's often more than one reason.
"The cases that do make it through to the disciplinary process often involve behaviour other than inappropriate prescribing of drugs - some of the doctors had inappropriate relationships with patients," she told Newshub.
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Most doctors caught were men who had been in general practice for more than 24 years, and it wasn't usually clear who the drugs were for. In some cases it was a lover or family.
Some doctors prescribed themselves drugs like zopiclone (a sleeping pill), sibutramine (an appetite suppressant) and pethidine (an opioid painkiller).
The biggest fine dished out was $15,000 for inappropriately prescribing pseudoephedrine. That doctor also had their registration cancelled.
Other drugs wrongly prescribed include codeine, morphine, temazepam and fentanyl, a drug linked to the deaths of music stars Prince, Tom Petty and Mac Miller.
Few of the 25 cases came to light through reporting from the doctor's colleagues, the research found, "despite colleagues being required to notify the authorities if they believe a doctor is 'unable to perform - because of some mental or physical condition'".
Dr Wallis says being disciplined doesn't always end a doctor's career, but often does - and that needs to change.
"They can certainly return to practise and have satisfying and long careers, so we need to possibly be thinking about doing more to support our colleagues and get them the necessary help."
In seven cases the doctor received name suppression.
The research was published Friday in the NZ Medical Journal.