Big drug companies are spending thousands of dollars educating doctors about expensive medications for depression, osteoporosis and overactive bladder that are not necessarily considered the preferred treatment, a new report has found.

Key points: Pharmaceutical companies spending thousands educating doctors on expensive drugs

Pharmaceutical companies spending thousands educating doctors on expensive drugs University of Sydney academics concerned about overdiagnosis and overtreatment

University of Sydney academics concerned about overdiagnosis and overtreatment Medicines Australia says engagement with drug companies is an important part of a doctors' ongoing education

In one case, researchers found a company spent more than $11,000 on a private dinner for 18 specialists at a top Sydney restaurant to discuss a new drug.

One of the report's authors, University of Sydney senior lecturer Barbara Mintzes, said attendance at these educational events could potentially lead to overtreatment, or lead doctors to prescribe less effective drugs.

"Our concern is that the information that doctors are getting at those sponsored events is not necessarily going to be leading to the best quality treatment," she said.

The research, by the university's Charles Perkins Centre for Evidence, Policy and Influence, looked at events for health workers for the three conditions: depression, osteoporosis and overactive bladder.

That's because these conditions are all, "highlighted in medical literature as potentially subject to overdiagnosis and overtreatment".

The report found prescribing rates for a new medication for overactive bladder, Mirabegron, which is not on the Pharmaceutical Benefits Scheme (PBS), tripled from mid-2014 to mid-2015.

"All anticholinergic overactive bladder drugs have modest benefits … with frequent dry mouth and constipation and there is observational evidence of dementia risk with longer-term use," the authors said.

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Prescribing rates of drugs in educational events going up: study

The research, published in the medical journal BMJOpen, revealed large increases in prescribing rates for many of the medications discussed at educational events.

Ms Mintez said prescriptions for the antidepressant drug agomelatine — known as Valdoxan — tripled from 2012 to 2015.

The findings have renewed calls for doctors' educational events to be free from commercial sponsorship. ( AAP: Melanie Foster, file photo )

The drug is not subsidised on the PBS and is expensive for patients.

Robert Djundjek, medical director of the company that makes Valdoxan, said medical education was necessary as the drug was the first in a new class of antidepressants, which work on targeting disrupted circadian rhythms.

"A program of medical education was not only appropriate, but entirely responsible for general practitioners and psychiatrists," he said.

Sales of another drug, which was the focus of almost 80 events, the long-acting form of anti-psychotic Seroquel, increased from 247,000 units in 2012 to 374,000 units in 2015.

"A 2012 … systematic review found that Astra-Zeneca's atypical antipsychotic quetiapine (Seroquel) had limited efficacy evidence for depression," the report's authors said.

Ms Mintez said several of the depression drugs were considered unacceptable for PBS reimbursement.

"Others have been associated with cost, efficacy and safety concerns internationally," she said.

Astra Zeneca did not respond to requests for comment.

Astellas, the makers of Mirabegron, said it believed supporting ongoing education was extremely important to ensure healthcare practitioners' knowledge of their products was comprehensive and up-to-date.

Industry body rejects report 'insinuation'

A spokesman for the pharmaceutical industry body, Medicines Australia, said engagement with pharmaceutical companies was an important and legitimate part of a medical practitioner's ongoing education.

"This [research] article relies heavily on insinuation and seeks to misinform the reader about the medicines being prescribed with no applicable Australian evidence whatsoever," she said.

"Suggestions like those expressed in the BMJ article do nothing but undermine a patient's confidence in a robust and accountable system, and call healthcare professionals into disrepute."

But the findings have renewed academics' calls for doctors' educational events to be free from commercial sponsorship.

The research found most often it was GPs attending the educational events, which were held as dinners at restaurants, rather than in a hospital or clinic.

More than 100,000 medical professionals attended 3,000 events in four years, to September 2015.

Royal Australian College of GPs president Dr Bastian Seidel said all RACGP members were trained to appraise evidence whether it was presented to them at events, or in journal papers and the media.

"Commercial interests should never inform the clinical decision-making of healthcare practitioners in Australia, including the commercial interest of pharmaceutical companies," he said.

Patients should consult their doctor before changing or stopping any medications.