Pharmaceutical Research

Impact of direct-to-consumer advertising on drug use varies depending on the drug, scope of advertising, and culture

The United States and New Zealand are currently the only countries that allow direct-to-consumer advertising (DTCA) of drugs. In fact, the U.S. Senate recently considered legislation forbidding such advertising during the first 2 years after release of a new drug-the period when safety problems undiscovered during clinical trials typically appear. Both proponents and opponents of DTCA assume that it increases use of the drugs advertised. However, a new study suggests that the impact of DTCA on drug use may be varied and limited, and that its impact on prescribing remains conjecture. For example, it found that DTCA did not increase use of two of three drugs studied. The researchers examined differences in the number of filled prescriptions for three heavily marketed drugs between English-speaking and French-speaking (control) Canadian provinces before and after the start of DTCA for the drugs in the United States. The drugs were etanercept, used for rheumatoid arthritis; mometasone, a nasal spray to treat allergies; and tegaserod, used to treat irritable bowel syndrome and constipation.

The DTCA campaign did not increase prescription rates for etanercept and mometasone. In contrast, tegaserod prescriptions increased 42 percent (0.56 per 10,000 residents) in English-speaking provinces immediately after the start of the U.S. campaign. Analysis of U.S. Medicaid data showed an even larger 56 percent increase in tegaserod prescriptions. Yet, this was the drug that was removed from the market a short time later due to evidence that it increased risk of heart attacks and strokes. However, this boost in prescriptions did not persist over time in either country, despite continued advertising.

The findings do suggest illicit exposure of Canadians to U.S. DTCA, an issue that may assume greater importance due to the growth of advertising over global mediums such as the Internet. The study was supported in part by the Agency for Healthcare Research and Quality (HS10391).

See "Effect of illicit direct to consumer advertising on use of etanercept, mometasone, and tegaserod in Canada: Controlled longitudinal study," by Michael R. Law, Sumit R. Majumdar, M.D., M.P.H., and Stephen B. Soumerai, Sc.D., in the September 2, 2008, British Medical Journal. The article is available online at www.bmj.com.

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