Drug-dependent doctors pose more of a risk to themselves than they do to patients, say researchers.
In the New Zealand Medical Journal today, Auckland University researchers say disciplinary cases for inappropriate prescribing by doctors in New Zealand are not common, but "the consequences can be dire".
Disciplinary charges against doctors are heard by the Health Practitioners Disciplinary Tribunal, and prior to 2004 also by the Medical Practitioners Disciplinary Tribunal.
A doctor may be found guilty of "any act or omission that, in the judgment of the tribunal, amounts to malpractice or negligence ... or ... has brought or was likely to bring discredit to the profession".
The researchers studied disciplinary cases against doctors in the 20 years until 2016 and found 11 percent of all cases included inappropriate prescribing of drugs of dependence.
They said the alleged misconduct "was diverse and often involved misconduct in addition to inappropriate prescribing, including sexual relations with patients and forging of a colleague's signature.
"It was not always clear in the decision for whom the appropriately-prescribed drugs were intended, although in some cases it was clear the drugs were not for self-use."
The drugs involved included opioids (pethidine, codeine, morphine, dextropropoxyphene, oxycodone, tramadol and fentanyl); benzodiazepines, pseudoephedrine and sibutramine.
Eighty percent of the doctors involved were male, say the researchers, most of them working in general practice.
As well, most of the doctors had been in practice for a long time, "with a mean of 24 years between qualification and discipline".
The misconduct was diverse, and was reflected on a diversity of penalties.
Six doctors were struck off the register over the period, 11 were suspended for between three and 24 months, and most of the rest had conditions imposed on their practice.
In 28 percent of cases, the doctor was given name suppression, one of them on appeal.
Pharmacies were the most common source of notification about the behaviour to the authorities.
The researchers said: "Patient harm was not a strong feature. It may be that drug-dependent doctors pose a greater risk to themselves than they do the health and safety of the public."
Katharine Wallis, a senior lecturer in general practice and primary healthcare at the university's School of Population Health and lead author of the study said: "Some of these cases, you know their family lives have broken down, they were isolated.
"I mean drug dependence is obviously not a good idea for anybody and doctors are no different.
"But in addition for doctors it can have implications for their ability to earn an income and things."
Dr Wallis also said it was a sad thing for the doctors, and although there were not many of them, many had been working as doctors for a long time.
"It's not evident how long they had issues with drug dependence or whatever.
"And I think it's an indication that the disciplinary process is often reserved as a place of last resort, and for many of those doctors who'd been in practice for a long time, it was one way of spelling the end of their careers really."