Your article (Doctors find drug that is better than aspirin at preventing heart attacks, 31 August) is of great interest. It cites a study that proposes replacing aspirin, the cornerstone of antiplatelet therapy for individuals at high risk of heart attacks and strokes, with clopidogrel. We must point out, however, that clopidogrel does not work uniformly across individuals. Although mentioned in the Lancet publication, it was only lightly considered in the Guardian article.
Clopidogrel is a prodrug. To work, it needs to be metabolised by a liver enzyme that varies in the population because of variations in the CYP2C19 gene. Most individuals have “normal” or “supra-normal” levels of the enzyme and clopidogrel works as expected. However, “intermediate metabolisers” activate clopidogrel less efficiently and “poor metabolisers” struggle to activate clopidogrel at all. For these people, clopidogrel may not provide enough protection against heart attacks or strokes.
