Variation in thromboxane B2 concentrations in serum and plasma in patients taking regular aspirin before and after clopidogrel therapy. (February 2015)

• Record Type: Journal Article
• Authors: Good, Richard I. S.; McGarrity, Anne; Sheehan, Rory; James, Tina E.; Miller, Helen; Stephens, Jonathan; Watkins, Stuart; McConnachie, Alex; Goodall, Alison H.; Oldroyd, Keith G.
• Is Part Of: Platelets. Volume 26:Number 1(2015:Feb.)
• Page Start: 17
• Page End: 24
• Publication Date: 2015-02
• Subjects: Blood platelets -- Periodicals; Blood Platelets -- Periodicals; 615.39
• DOI: 10.3109/09537104.2013.870334
• Languages: English
• ISSNs: 0953-7104

Abstract

<abstract> <title>Abstract</title> <p>Dual antiplatelet therapy with aspirin and a P2Y<sub>12</sub> antagonist is widely prescribed for the prevention of thrombotic events in patients with an acute coronary syndrome or undergoing percutaneous coronary intervention (PCI). It is recognised that there is inter-individual variation in the antiplatelet effects of both drugs. Recent data also suggest that P2Y<sub>12</sub> antagonists can affect the response to aspirin. A direct indicator of the effect of aspirin on platelets is their ability to generate thromboxane, which if measured as the difference between the level of thromboxane B<sub>2</sub> in serum and plasma ([TxB2]<sub>S-P</sub>) avoids the confounding effect of endogenous TxB2 production from other cells. We therefore analysed [TxB2]<sub>S-P</sub> as a measure of aspirin response in a group of 123 patients undergoing elective PCI before and after the introduction of clopidogrel. In a subgroup of 40 patients taking aspirin alone, we compared [TxB2]<sub>S-P</sub> and VerifyNow Aspirin for the assessment of aspirin response. There was a wide variation in plasma and serum TxB2 concentrations both before and after clopidogrel therapy but only 3.5% of patients had residual serum concentration of TxB2 > 10 ng/ml. There was a strong correlation between the pre and post clopidogrel levels of TxB2 (<italic>r</italic> ≥ 0.78; <italic>p</italic> = 0.001) and no significant difference in [TxB2]<sub>S-P</sub>. There was no correlation between the magnitude of response to clopidogrel response and the generation of thromboxane B2. Correlation between [TxB2]<sub>S-P</sub> and VerifyNow Aspirin was poor. We conclude that the use of a P2Y<sub>12</sub> antagonist does not influence the effect of aspirin on the ability of platelets to generate thromboxane. Therefore, measurement of TxB2 levels in serum, after subtracting the contribution from plasma, provides a measure of the response to aspirin in patients taking dual antiplatelet therapy.</p> </abstract>