A new study has revealed that under the influence of pharmaceutical promotion, doctors are likely to prescribe more expensively, less appropriately and more often.
The findings have offered a broad look at the relationship between doctors' prescribing habits and their exposure to information provided by drug companies.
Researchers analyzed 58 separate studies of this phenomenon from Canada, the United States, Europe and Australia, dating from the 1960s.
"Many doctors claim they aren't influenced by the information provided by pharmaceutical companies. Our research clearly shows that they are and the influence is negative," said Joel Lexchin of the York University in Toronto.
"Unfortunately, patients are the ones getting a raw deal. If doctors are inundated with advertising from brand name companies, they are more likely to prescribe that brand name, regardless of whether it's best for the patient," said Lexchin.
Overall, researchers found no evidence that drug companies' promotional efforts improve prescribing behaviour in any way.
All but one of the studies suggested that exposure to promotional information was associated with lower prescribing quality; others detected no association.
Findings also show that promotional information led to more frequent prescribing; studies dealing with this correlation either showed a spike in prescribing or detected no association.
Researchers also established a link between promotion and higher prescribing costs.
"In Canada, companies are estimated to be spending anywhere between 2.4 and 4.75 billion dollars annually on promotion, one of the major reasons why spending on brand name drugs was rising at a rate of just under 10 per cent annually until two years ago," he said.
"Although we didn't find any evidence of improvements in prescribing due to promotional information, that doesn't entirely exclude the possibility that prescribing might sometimes be improved," he added.
The findings were published in the journal PLoS Medicine.