PLOS Medicine has just published another systematic review on this topic. Although the review purports to be an update on prior reviews, it contains little in the way of new information. In fact it ignores the most significant new research findings in the field. More on that below. The conclusion reads:
With rare exceptions, studies of exposure to information provided directly by pharmaceutical companies have found associations with higher prescribing frequency, higher costs, or lower prescribing quality or have not found significant associations. We did not find evidence of net improvements in prescribing, but the available literature does not exclude the possibility that prescribing may sometimes be improved. Still, we recommend that practitioners follow the precautionary principle and thus avoid exposure to information from pharmaceutical companies.
Although no conflict of interest statement was included in the paper there are significant concerns about at least two of the authors, Peter Mansfield and Joel Lexchin. I have no doubts about the honesty of these authors but they are (like the rest of us) biased. In the case of these particular two authors the bias is heavily negative towards interactions between the medical profession and the pharmaceutical industry. Both, in one way or another, have campaigned over the last decade to drum up public opposition to physician-pharma interactions. Both were involved in the No Free Lunch initiative. Having participated in the No Free Lunch listserv with these authors I can imagine the presuppositions they must have brought to this analysis.
Despite this bias, the authors apparently felt the evidence was inconclusive and had to base their recommendations against interaction on the precautionary principle (assume the worst and play it safe).
In my Medscape Roundable piece a couple of years ago I explained what was wrong with the published literature on this subject (my emphasis):
Studies in support of this argument do not give a balanced view. Surveys of the effects of drug detailing on doctors' prescribing have focused selectively on areas of overuse, such as antibiotics in the ambulatory setting and new expensive drugs compared with equally effective generics. Although some promotions undermine evidence-based practice, others may enhance it. Because promotional literature is a mix of good and bad information, the net effect on patient care is not known. Many heavily promoted treatments are evidence-based and known to be underutilized by doctors. A good example is the inadequate use of low-molecular-weight heparin for thromboembolism prophylaxis. The promotion of statin drugs[12-14] and angiotensin-converting enzyme inhibitors for appropriate patients[15-17] is another example. Such a promotion toward best practice has been ignored in published studies. Research in a broader range of clinical situations is needed before conclusions can be made about the overall effect on evidence-based practice.
Unfortunately opportunities for much of this research have been lost, because many evidence-based treatments have gone generic and are no longer promoted in the way they once were and the pipeline for truly innovative drugs is running pretty dry at the moment. In that same Medscape piece I also argued that none of the studies on the effects of promotion looked at outcomes. Since I wrote that piece there has been one very important study on industry supported promotion of evidence-based practice, and it looked at clinical outcomes. I am referring, of course, to the Surviving Sepsis Campaign, one of the most maligned industry campaigns in all of medicine. Suffice it to say, (for background see posts here, here and here) the campaign was associated with better adherence to evidence-based practice and reduced mortality. For Steve Novella's take at Science Based Medicine go here.