Evening aspirin intake results in higher levels of platelet inhibition and a reduction in reticulated platelets - a window of opportunity for patients with cardiovascular disease?

Cardiovascular events occur most frequently in the early morning. Similarly, the release of reticulated platelets (RP) by megakaryocytes has a peak in the late night and early morning. Which aspirin regimen most effectively inhibits platelets during these critical hours is unknown. Hence, the primary objective of this trial was to assess platelet function and RP levels at 8.00 AM, in stable cardiovascular (CVD) patients, during three different aspirin regimens. In this open-label randomized cross-over study subjects were allocated to three sequential aspirin regimens: once-daily (OD) 80 mg morning; OD-evening, and twice-daily (BID) 40 mg. Platelet function was measured at 8.00 AM & 8.00 PM by serum Thromboxane B2 (sTxB2) levels, the Platelet Function Analyzer (PFA)-200® Closure Time (CT), Aspirin Reaction Units (ARU, VerifyNow®), and RP levels. In total, 22 patients were included. At 8.00 AM, sTxB2 levels were the lowest after OD-evening in comparison with OD-morning (p =