Variability of the antithrombotic effect of acetylsalicylic acid with the administration of different dosages: reality or myth?

Abstract Introduction We rely on the antithrombotic effect of acetylsalicylic acid (ASA) in a number of pathologies, although other beneficial effects are known, such as its anti-inflammatory properties, when administered in higher doses (500mg, 1000mg per os). However, whether the anti-inflammatory effect decreases the antithrombotic potency of ASA is not known. This gap in evidence may lead to an unnecessary use of two drugs (one antithrombotic and one anti-inflammatory) that could be replaced by ASA alone. This scenario presents frequently: post-infarct pericarditis or when in doubt between non-ST segment elevation myocardial infarction vs myopericarditis. In such cases, the use of ASA could assure both antithrombotic and anti-inflammatory effects. Since the antithrombotic effect of ASA is not scientifically proved for higher doses, currently we use ASA 100mg as an antithrombotic agent and ibuprofen as an anti-inflammatory. This experimental study intends to assess whether ASA maintains its antithrombotic effect when administered in an anti-inflammatory dose. Methods Twenty healthy volunteers were recruited. They all had their platelet function assessed in a qualitative manner, using PFA-200 Innovance technology. The volunteers were randomized into four groups, with 5 participants each. The participants of groups 1, 2, 3 and 4 ingested ASA 100mg, 300mg, 500mg and 1000mg respectively, in a blind experiment. One hour after ingestion (peak of action), the volunteers’ platelet function was reassessed. PFA-200 evaluates platelet function through platelet occlusion time (OT), which is measured in milliseconds (ms). Normal platelet function translates into OT of 82-150ms. If the OT is higher than 150ms, the patient is anti-aggregated. Results Prior to ASA administration, 19/20 volunteers had OT within the reference range. Afterwards, in all four groups, volunteers reached OT > 150ms, regardless of the ASA dose administered. Mean OT values for each group were 188ms [SD-23] , 205ms [SD-63], 262ms[SD-44] and 232ms [SD-47], respectively. Overall SD was 32ms. Conclusion ASA maintains its antithrombotic effect when administered in an anti-inflammatory dose. There is no clear correlation between the potency of antithrombotic effect and the ASA dose administered. This was a pilot study that supports the maintenance of the antithrombotic effect of ASA in higher doses, but further and larger studies are required to corroborate these results.