Background: Cytochrome P450 inhibition by proton pump inhibitors (PPIs) may attenuate the effectiveness of clopidogrel.
Aim: To examine whether PPI use modifies the association between clopidogrel use and major adverse cardiovascular events (MACE) after percutaneous coronary intervention (PCI) with stent implantation, using time-varying drug exposure ascertainment.
Methods: We conducted this population-based cohort study in Western Denmark (population 3 million) using medical databases. We identified all 13,001 patients with coronary stent implantation between 2002 and 2005 and ascertained their reported comorbidities. During the recommended 12-month postintervention treatment period, we tracked use of clopidogrel and PPI and the rate of MACE. We used Cox regression to compute hazard ratios (HRs), controlling for potential confounders.
Results: During follow-up, one or more prescriptions were redeemed by 91% of patients for clopidogrel and by 21% of patients for PPIs. Of the patients, 15% experienced a MACE. The adjusted HR for MACE comparing clopidogrel use with non-use was 0.57 [95% confidence interval (CI): 0.44-0.74] among PPI users and 0.47 (95% CI: 0.42-0.53) among PPI non-users, yielding an interaction effect (i.e. relative rate increase) of 1.20 (95% CI: 0.91-1.58). PPI users treated from before PCI had a 25% increased rate of MACE compared to PPI non-users, independent of clopidogrel use [adjusted HR = 1.24 (95% CI: 0.97-1.58) for clopidogrel users and 1.26 (95% CI: 0.97-1.63) for clopidogrel non-users].
Conclusions: The use of PPIs as a class did not modify the protective effect of clopidogrel, but its use was associated with major adverse cardiovascular events itself, particularly among patients having used PPIs before percutaneous coronary intervention.
© 2011 Blackwell Publishing Ltd.