Participation in clinical trials does not appear to affect physician's adherence to guidelines

June 20, 2006

Physicians who participated in a pharmaceutical-sponsored clinical trial involving asthma medications maintained adherence to treatment guidelines but were more likely to prescribe the sponsor's drugs, according to a study in the June 21 issue of JAMA.

Pharmaceutical companies are frequently involved in clinical trials in general practice, and this may trigger an increase in the use of the sponsoring company's products due to the physicians' experience with these products. This effect may be further strengthened by close physician-company cooperation, which may create physician loyalty toward the company. The effect of participation in company-sponsored studies on drug preferences has not been evaluated in primary care.

Morten Andersen, M.D., Ph.D., of the University of Southern Denmark, Odense, and colleagues investigated the effects of physicians participating in a pharmaceutical company-sponsored clinical trial that was aimed at improving patients' use of asthma medicine. The study compared 10 practices that were conducting the trial on asthma medicine with 165 control (non-trial-conducting) practices in Funen County, Denmark. The study included 5,439 patients treated with asthma drugs from the trial-conducting practices and 59,574 patients from the control practices.

The researchers found that the prevalence of inhaled steroid use among asthma patients increased from 68.5 percent at baseline to 72.9 percent during the second observation year in trial-conducting practices and from 69.1 percent to 73.3 percent in control (non-trial-conducting) practices. There was no impact of participating in the trial on physicians' adherence to international treatment guidelines. Both trial-conducting and control practices had a gradually increased use of the trial sponsor's inhaled corticosteroids, from 74.8 percent to 81.5 percent in trial-conducting practices and from 73.6 percent to 76.6 percent in control practices. Trial-conducting practices were 26 percent more likely than control practices to have the trial sponsor's inhaled corticosteroids used. The trial sponsor's share of the total prescribed volume of asthma drugs increased in trial-conducting practices compared with control practices by 6.7 percent.

"Our study confirms the hypothesis that physician involvement in clinical trials is a powerful tool for influencing company-specific drug preferences. Several mechanisms may be responsible, including setting up a gift relationship by payment to the trial-conducting physicians. If we had access to information on the costs of the trial, it would have been possible to evaluate if these trial costs were counterbalanced by the revenue from the trial sponsor's increased market share. Whether conducting a clinical trial can lead to minor improvements in guideline adherence can only be addressed in large-scale studies," the authors write.
(JAMA. 2006;295:2759-2764. Available pre-embargo to the media at

Editor's Note: For funding/support and financial disclosure information, please see the JAMA article.

Editorial: Clinical Trial Investigators and Their Prescribing Patterns

In an accompanying editorial, Bruce M. Psaty, M.D., Ph.D., of the University of Washington, Seattle and Drummond Rennie, M.D., of the University of California, San Francisco, and Deputy Editor, JAMA, comment on the findings of Andersen et al.

"With the advent of national drug prescription data from Medicare Part D, the association between investigator status and prescribing behavior may emerge as the subject of a new genre of studies on research into physician-industry interactions in the United States. Practicing physicians and disinterested scientists need to recognize and acknowledge these forms of potential influence by the pharmaceutical industry. Agreeing to work as an investigator in industry-sponsored trials may represent a commitment to an effort that is more or less a scientific endeavor and, at the same time, a marketing initiative."

"More importantly, the scientific rationale for launching thousands of small short-term trials remains unclear. The health of the public would be better served by the conduct of fewer small short-term studies and more well-designed large long-term trials, such as the Women's Health Initiative (WHI) and the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), that fully address the health risks and benefits of pharmacological therapies used for chronic conditions. The findings from such studies provide a sensible evidence base for both clinical practice and industry marketing."

(JAMA. 2006;295:2787-2790. Available pre-embargo to the media at

Editor's Note: This research was supported in part by grants from the National Heart, Lung, and Blood Institute, the National Institute on Aging, and the American Heart Association. Dr. Psaty reported receiving compensation for expert testimony on phenylpropanolamine and on cerivastatin.

The JAMA Network Journals

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