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Calcium channel blockers reduce the antiplatelet effect of clopidogrel

BMC Pharmacology
Springer (Biomed Central Ltd.)
Publication Date
DOI: 10.1186/1471-2210-8-s1-a47
  • Meeting Abstract
  • Biology
  • Medicine

Abstract BioMed Central Page 1 of 1 (page number not for citation purposes) BMC Pharmacology Open AccessMeeting abstract Calcium channel blockers reduce the antiplatelet effect of clopidogrel Jolanta M Siller-Matula*1, Irene Lang2, Günter Christ2 and Bernd Jilma1 Address: 1Department of Clinical Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and 2Department of Cardiology, Medical University of Vienna, 1090 Vienna, Austria Email: Jolanta M Siller-Matula* - [email protected] * Corresponding author Background Clopidogrel is activated by CYP3A4 which also metabo- lizes calcium channel blockers of the dihydropyridine class. Due to the known CYP3A4 inhibition by calcium channel blockers, we hypothesized that there might be a drug-drug interaction between clopidogrel and dihydro- pyridines in patients with coronary artery disease. Materials and methods Responsiveness to clopidogrel was assessed by the vasodi- lator stimulated phosphoprotein (VASP) phosphoryla- tion assay and aggregometry in 200 patients with coronary artery disease undergoing percutaneous coro- nary intervention. Results The platelet reactivity index (PRI in the VASP assay, nor- mal range 69–100%) was higher in patients on both clopidogrel and calcium channel blockers (61%) as com- pared to patients on clopidogrel without calcium channel blockers (48%). The absolute difference was 13% (95%CI: 6–20%; p = 0.001) and the relative difference approached 21%. A reduced effect of clopidogrel (PRI >69%) was seen in 40% of patients with concomitant cal- cium channel blocker treatment compared to 20% with- out (χ2-test: p = 0.008). Intake of calcium channel blocker remained an independent predictor of reduced platelet inhibition by clopidogrel after adjustment for cardiovas- cular risk factors. This corresponded to an increased plate- let aggregation of similar magnitude (p < 0.05) and was associated with adverse clinical outcome. In vitro incuba- tion with calciu

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