Direct-to-consumer (DTC) drug advertising may not have the impact that drug companies hope for. The ads have only a modest effect on the sale of drugs, according to research published by the BMJ, a British medical journal.

DTC drug ads are allowed in only two countries, the United States and New Zealand. In 2006, U.S. pharmaceutical companies spent about $5 billion on consumer marketing campaigns.

The research was conducted in Canada, where DTC advertising is illegal but where English speakers hear and see U.S. ads. French-speaking Quebec acted as a control group. Researchers looked at whether the use of several advertised drugs increased faster in the English-speaking regions.

Prescription rates for Enbrel and Nasonex remained the same in both communities, and while sales of Zelnorm initially spiked in English-speaking regions, after a few years they resumed following the same pattern as the French-speaking regions.