In Vitro Effects of Pantoprazole on Platelet Aggregation in Blood Samples From Clopidogrel and Aspirin-treated Patients

Platelet inhibition during treatment with the antiplatelet drug clopidogrel is prone to great interindividual variability and is believed to be affected by several factors such as genetics and drug-drug interactions. Proton pump inhibitors have been shown to interfere with the liver metabolism of clopidogrel. However, there are limited data on any direct effects proton pump inhibitors may have on clopidogrel. The aim of the study was to evaluate whether the in vitro addition of pantoprazole affects platelet aggregation in blood samples from clopidogrel and aspirin-treated patients. Blood samples were drawn from 66 patients on clopidogrel and aspirin who underwent coronary angiography. Platelet aggregation was analyzed using the bed-side Plateletworks assay before and after the addition of 2 different amounts of pantoprazole. The addition of 2.5 mL (4 mg/mL) pantoprazole, final concentration 0.01 mg/mL, was followed by a significant reduction (26%, P <= 0.001) of platelet aggregation, which was further reduced (39%, P <= 0.001) when a higher dose, 10 mL (4 mg/mL), final concentration 0.04 mg/mL, was added. In conclusion, platelet aggregation was significantly decreased by in vitro addition of pantoprazole. To explore the clinical relevance of this, future studies are needed.