Are there public health consequences when regulators turn a blind eye to cross border advertising that contravenes national laws? Although Canada prohibits direct to consumer advertising of prescription drugs, no steps are taken to prevent US advertising from reaching the Canadian public. The linked study by Law and colleagues (doi: 10.1136/bmj.a1055), provides compelling evidence that this does have consequences for public health and of the need for better regulatory oversight.1

Direct to consumer advertising from the United States reaches Canadians via cable television and US magazines sold in Canada. Law and colleagues found that cross border advertising increased prescribing of a minimally effective drug with a poor safety profile,2 which subsequently led to its withdrawal.3

French speaking Canadians, who mainly live in Quebec, watch less US television than their English speaking compatriots and are less exposed to US direct to consumer advertising. Law and colleagues used this difference to examine the effects of US advertising campaigns on prescribing rates. Three drugs met the inclusion criteria of the study on the basis of timing of approval and advertising—tegaserod, etanercept, and mometasone. A clear effect was …