According to a new study, Direct-to-Consumer advertising has little effect on the sale of drugs.

In five years of follow-up, researchers looked at the prescription rates of three drugs - Enbrel (for rheumatoid arthritis), Nasonex (for nasal allergies) and Zelnorm (for irritable bowel syndrome) - in Canada, where, although DTC ads are banned, the inhabitants usually follow them on U.S. cable and satellite TV stations.

Michael Law, a health policy researcher at Harvard Medical School in Boston, Massachusetts, and his team, compared the prescription rates in French-speaking Quebec with the English-speaking other parts of Canada, with the aim of finding out if the intake of these three medicines showed a bigger increase in the English-speaking areas after the promotion of the prescription drugs.

What researchers found is that sales for Enbrel and Nasonex remained at a steady level in both communities, while prescription rates of the other drug at first rose in English-speaking areas but, after a period of some years, their level was similar to that of the French-speaking areas.

The findings point out to the idea that DTC ads don’t lead to an increase in the number of drug sales. The most probable reason is that, in order to procure the medicines, customers should receive first a prescription from their doctors. Therefore, taking into account the results, drug ads may be regarded as a waste of money.

However, direct-to-consumer drug advertising does "a good job of driving people into the doctor's office, raising awareness of symptoms that the patient might have," according to Lori Reilly, vice president for policy and research at the Pharmaceutical Research and Manufacturers Association.