Even so, many of the doctors surveyed said they were likely to start prescribing or increase prescriptions of promoted drugs following sales rep visits, consistent with previous research that shows prescribing behaviour is influenced by pharmaceutical companies' promotion.
"Harm from medication use is a serious public health concern," said Barbara Mintzes, principal researcher of a survey study. "So the information quality and doctors getting complete information on medicines is important."
For the study, published online Wednesday in the Journal of General Internal Medicine, the researchers asked 255 family doctors in Montreal, Vancouver, Sacramento and Toulouse, France, to fill out a questionnaire each time they were visited by a drug company rep.
In all, the physicians provided information on almost 1,700 drug promotions between May 2009 and June 2010.
Pharmaceutical sales reps regularly visit doctors' offices to promote their products — providing information, often free samples and, in some cases, food and invitations to events. Since 2005, France has prohibited free drug samples and gifts to doctors.
"We were interested to know how often the information that was being provided to doctors met a minimum standard for drug safety information," said Mintzes, who works at the school of population and public health at the University of British Columbia.
"We actually set the bar quite low," she said from Vancouver.
This "minimally adequate safety information" included at least one serious risk from a medication, at least one common side-effect, at least one contra-indication — in other words, the type of patient who should not take the drug — and at least one approved use for the product.
"What we found was that that information was hardly ever being provided," she said. Overall, "it was provided in less than two per cent of the promotions to doctors."
Physicians in Toulouse were more likely to be told of a harmful effect by sales reps than were doctors in Canada and the U.S., possibly reflecting stricter regulatory standards for promotion of medicines in France, researchers said.
In Vancouver and Montreal, potential harms were mentioned for 34 per cent of promoted medications, compared with 61 per cent in Toulouse. In Sacramento, possible harms were brought up for 39 per cent of products.
Information on health benefits was provided by reps twice as often as information on adverse effects, "with not a single harmful effect mentioned in over half of promotions in the three North American sites," the researchers write.
"Laws in all three countries require sales representatives to provide information on harm as well as benefits," noted Mintzes. "But no one is monitoring these visits and there are next to no sanctions for misleading or inaccurate promotion."
Serious risks were mentioned in only six per cent of the promotions, even though 57 per cent of the medications involved in these visits came with Health Canada boxed warnings or U.S. Food and Drug Administration "black box" advisories — the strongest warnings issued in both countries.
"We are very concerned that doctors and patients are left in the dark and patient safety may be compromised," she said. "There's a serious problem in terms of ensuring that doctors are getting adequate safety information as a background to prescribing decisions."
Indeed, previous studies have shown that doctors are often influenced by drug rep promotions — even though most physicians believe they are not affected by such sales pitches — and this study seems to bear out that conclusion.
"We were surprised that most of the time they were somewhat or very likely to increase their prescribing or to start prescribing (a promoted drug)," despite receiving inadequate safety information, Mintzes said of doctors surveyed for the study.
"The problem is this is a source of information that is often used, consciously or not, to inform prescribing decisions."
Dr. Tom Perry, an internal medicine and clinical pharmacology specialist at the UBC Hospital in Vancouver, expressed concern about the findings.
"Doctors learn relatively little about drugs in medical school and much of their exposure to pharmacology after graduation may be in the form of advertising," said Perry, who was not involved in the study. "If they are unaware of the potential harms from drugs they prescribe, patients inevitably suffer the consequences."
But the president of Rx&D, the association representing Canada’s research-based pharmaceutical companies, described regulations surrounding adverse drug effects as "very strict."
"Pharmaceutical companies are required to advise Health Canada of any undesired or unwanted effects," Russell Williams said in an emailed statement. "These are also communicated to health professionals so that they can take this information into consideration when treating Canadians."
Williams said Rx&D’s Code of Ethical Practices sets out clear guidelines to ensure that health-care professionals have access to information "about the appropriate uses of our products and services, and that this information is accurate ... fair (and) balanced."