Clopidogrel is an oral antiplatelet prodrug, the majority of which is hydrolyzed to an inactive metabolite by hepatic carboxylesterase 1 (CES1). Most angiotensin-converting enzyme inhibitors (ACEIs) are also metabolized by this enzyme. We examined the effects of ACEIs on clopidogrel bioactivation in vitro and linked the results with a pharmacoepidemiological study. In vitro, ACEIs inhibited CES1-mediated hydrolysis of a model substrate, and trandolapril and enalapril increased formation of clopidogrel active metabolite. In 70,934 patients with myocardial infarction, hazard ratios for clinically significant bleeding in ACEI-treated patients cotreated with or without clopidogrel were 1.10 (95% confidence interval (CI): 0.97-1.25, P = 0.124) and 0.90 (95% CI: 0.81-0.99, P = 0.025), respectively, as compared with patients who did not receive ACEIs. This difference was statistically significant (P = 0.002). We conclude that cotreatment with selected ACEIs and clopidogrel may increase the risk of bleeding. Combination of in vitro and pharmacoepidemiological studies may be a useful paradigm for assessment of drug-drug interactions.
OBJECTIVES: To compare the cardiovascular safety of currently marketed dementia medications in new users in the United States and Denmark. DESIGN: Retrospective cohort study. SETTING: Nationally representative sample of Medicare beneficiaries from 2006 through 2009 and nationwide Danish administrative registries from 1997 through 2007. PARTICIPANTS: Individuals treated with a dementia medication aged 65 and older. MEASUREMENTS: Hospitalizations for myocardial infarction (MI), heart failure, and syncope or atrioventricular block in both cohorts; fatal or nonfatal MI and cardiac death in the Danish cohort; and all-cause mortality in sensitivity analyses. RESULTS: In 46,737 Medicare beneficiaries and 29,496 Danish participants, donepezil was the most frequently used medication. There were no substantial differences in the risk of MI or heart failure between participants using donepezil and those using other cholinesterase inhibitors (all hazard ratios (HR) crossing 1). In the Danish cohort, memantine was associated with fatal or nonfatal MI (HR = 1.33, 95% confidence interval (CI) = 1.08-1.63), cardiac death (HR = 1.31, 95% CI = 1.12-1.53), and a trend toward higher rates of hospitalization for MI (HR = 1.31, 95% CI = 0.98-1.76). Memantine was also associated with greater risk of all-cause mortality in the Medicare (HR = 1.20, 95% CI = 1.13-1.28) and Danish (HR = 1.83, 95% CI = 1.73-1.94) cohorts, suggesting that sicker individuals were selected for memantine therapy. CONCLUSION: Cholinesterase inhibitors have similar cardiovascular risk profiles. Associations between memantine and fatal outcomes in Denmark may be related, in part, to selection of sicker individuals for memantine therapy.