Drug company information might influence prescribing habits

Information from drug companies influences doctors' decisions, and not necessarily positively, according to a meta-analysis.

Researchers reviewed studies of prescribing physicians who were exposed to sales visits, journal advertisements, attendance at pharmaceutical sponsored meetings, mailed information, prescribing software and participation in sponsored clinical trials. The outcomes measured were quality, quantity and cost of physicians' prescribing.

The meta-analysis included randomized controlled trials, time series analyses, before-after studies, cohort studies, case-control studies, ecological studies and cross-sectional studies. Studies were included if they both measured exposure to any type of information directly provided by pharmaceutical companies and physicians' prescribing. Studies were excluded if they looked at the indirect information, such as continuing medical education courses funded by unrestricted grants, or if they were case series, case reports, abstracts, news items and short reports.

Results were published Oct. 19 at PLoS Medicine.

Of the studies, 38 showed that exposure to drug company information resulted in more frequent prescriptions, while 13 did not. Among the many analyses of potentially influential factors:Of studies of pharmaceutical sales representative visits, 17 found an association with increased prescribing of the promoted drug. None found less frequent prescribing. Of the remaining 11, six had mixed results.Of the four studies that measured journal advertisements and included statistical tests, one found that journal advertisements had a more pronounced effect on market share for the advertised drug than did positive scientific information published in medical journals.Of eight studies of pharmaceutical company-sponsored meetings, five found positive associations with prescribing frequency and three did not.Of three studies of mailed promotional material, one found an association with increased prescribing and two did not.A single study that examined the effect of advertising in clinical practice software found no association with prescribing frequency for six medications and less prescribing of one medication.Several studies combined the outcome measures for various exposures to pharmaceutical company information or measured overall promotional investment, a proxy for the amount of exposure to information from pharmaceutical companies. Three studies found that total promotional investment was positively associated with prescribing frequency. Two studies found both positive results and no association. One study did not detect an association.

While the limitations of the original studies and of the nature of meta-analysis itself limit the researchers conclusions, researchers found some evidence of increased costs and decreased quality of prescribing. They did not find evidence of net improvements in the quality of prescribing associated with exposure to information from pharmaceutical companies. In the absence of such evidence, researchers wrote, “We recommend that practitioners follow the precautionary principle and thus avoid exposure to information from pharmaceutical companies unless evidence of net benefit emerges.”