Doctors are often asked by pharmaceutical companies to take part in clinical trials and little is known about the effects of such participation on their prescribing patterns.

It is often suspected by many of being a trigger for an increase in the use of the sponsoring company’s products due to the physicians’ familiarity with them.

Researchers in Denmark who investigated the effects of such participation in a pharmaceutical company-sponsored clinical trial by doctors, say that doctors are influenced by the trials and are more inclined to prescribe the drug.

Morten Andersen, M.D., Ph.D., of the University of Southern Denmark, Odense, and colleagues compared 10 practices in Denmark that were conducting a trial on asthma medicine with 165 control (non-trial-conducting) practices.

The trial was aimed at improving patients’ use of asthma medicine.

The study included 5,439 patients treated with asthma drugs from the trial-conducting practices and 59,574 patients from the control practices.

The trials were conducted between April 26, 2001, and October 7, 2002 and the Danish team say they found that although conducting a trial sponsored by a pharmaceutical company had no significant impact on physicians’ adherence to international treatment recommendations, it confirmed the hypothesis that physician involvement in clinical trials is a powerful tool for influencing company-specific drug preferences.

Use of inhaled steroids among asthma patients was found to have increased from 68.5 percent to 72.9 percent during the second year in the practices involved in the trial and from 69.1 percent to 73.3 percent in the other practices.

The study was sponsored by drug manufacturer AstraZeneca, Denmark.

The company contributed data for the trial, but was not involved in the study’s design and interpretation of the data.

The research is published in the current issue of the Journal of the American Medical Association.