Published 2 September 2008, doi:10.1136/bmj.a1055
Cite this as: BMJ 2008;337:a1055

Research

Effect of illicit direct to consumer advertising on use of etanercept, mometasone, and tegaserod in Canada: controlled longitudinal study

¹ Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, 133 Brookline Avenue, 6th floor, Boston, MA 02215, USA, ² Division of General Internal Medicine, Department of Medicine, 2E3.07 Walter Mackenzie Health Sciences Centre, University of Alberta Hospital, Edmonton, Alberta T6G 2B7, Canada

Objective To assess the impact of direct to consumer advertising of prescription drugs in the United States on Canadian prescribing rates for three heavily marketed drugs—etanercept, mometasone, and tegaserod.

Design Controlled quasi-experimental study using interrupted time series analysis.

Population Representative sample of 2700 Canadian pharmacies and prescription data from 50 US Medicaid programmes.

Main outcome measures Differences in number of filled prescriptions per 10 000 population per month between English speaking and French speaking (control) Canadian provinces before and after the start of direct to consumer advertising in the United States.

Results Spending on direct to consumer advertising for study drugs ranged from $194m to $314m (£104m-£169m; 131m-212m) over the study period. Prescription rates for etanercept and mometasone did not increase in English speaking provinces relative to French speaking controls after the start of direct to consumer advertising. In contrast, tegaserod prescriptions increased 42% (0.56 prescriptions/10 000 residents, 95% confidence interval 0.37 to 0.76) in English speaking provinces immediately after the start of US direct to consumer advertising. Uncontrolled analysis of US Medicaid data showed a larger 56% increase in tegaserod prescriptions. However, this increase did not persist over time in either country, despite continued advertising.

Conclusions Exposure to US direct to consumer advertising transiently influenced both Canadian and US prescribing rates for tegaserod, a drug later withdrawn owing to safety concerns. The impact of direct to consumer advertising on drug use seems to be highly variable and probably depends on the characteristics of the advertised drug, the level of exposure to direct to consumer advertising, and the cultural context.

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Rapid Responses:

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Advertising study beneath BMJ standards

David J Reinhardt
bmj.com, 8 Sep 2008 [Full text]

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