Clopidogrel is a prodrug with high inter-individual response variability. Clopidogrel is converted to an active drug in part through an enzyme encoded by the gene named CYP2C19. Individuals with genetically-impaired CYP2C19 metabolism have lower capacity to convert the prodrug to its active form. Consequently, these individuals have lower blood levels of the activated form of clopidogrel, diminished antiplatelet responses, and higher rates of cardiovascular events and stent thrombosis. Increasing doses of clopidogrel in such patients represents a possible approach to managing the gene-drug interaction.