Can resistance to aspirin be reversed after an additional dose?

Mechanism of Improving Aspirin Resistance: Blood-Activating Herbs Combined With Aspirin in Treating Atherosclerotic Cardiovascular Diseases

Atherosclerotic thrombotic disease continues to maintain a high morbidity and mortality rate worldwide at present. Aspirin, which is reckoned as the cornerstone of primary and secondary prevention of atherosclerotic cardiovascular diseases (ASCVDs), has been applied in clinics extensively. However, cardiovascular events continue to occur even though people utilize aspirin appropriately. Therefore, the concept of aspirin resistance (AR) was put forward by scholars, which is of great significance for the prediction of the clinical outcome of diseases. The pathogenesis of AR may be incorporated with low patient compliance, insufficient dose, genetic polymorphism, increased platelet transformation, inflammation, and the degenerative changes and calcification of platelets. The improvement of AR in the treatment of ASCVDs has gradually become a research hot spot in recent years. Traditional Chinese medicine (TCM) regards individuals as a whole and treats them from a holistic view, which has been found to have advantages in clinical studies on the treatment of AR. Many kinds of blood-activating TCM have the effect of improving AR. The potential mechanism for the improvement of AR by blood-activating herbs combined with aspirin was explored. The combination of blood-activating herbs and aspirin to improve AR is likely to turn into a hot topic of research in the future.

Platelet Function Tests Predicting the Efficacy and Safety of Aspirin Secondary Prevention

OBJECTIVE

To precisely prevent stroke, we evaluated three platelet function tests and their associations with clinical outcomes in ischemic stroke patients.

METHODS

On-treatment platelet reactivity of acute minor stroke patients taking aspirin plus clopidogrel was tested by light transmittance aggregometry (LTA), thromboelastography (TEG) and platelet function analyzer (PFA). Mann-Whitney U tests and receiver operating characteristic (ROC) curve analysis were used to assess their associations with recurrent events and clinical outcome prediction.

RESULTS

127 acute minor stroke patients were stringently selected and followed for 13 months. Eight patients (6.3%) self-reported the recurrence and 13 (10.2%) patients self-reported bleeding. Recurrent patients displayed significantly higher on-treatment platelet reactivity when measured with LTA (p = 0.030) and PFA (p < 0.001). Further ROC analysis demonstrated that LTA and PFA had modest-to-fair ability to predict stroke recurrence (LTA: area under the curve [AUC], 0.765; 95% CI, 0.584-0.945, PFA: AUC, 0.832; 95% CI, 0.658-1.000). However, TEG (measured by the platelet inhibition rate) could not detect the difference between recurrent patients and non-recurrent patients (p = 0.515) and predict recurrent events (AUC, 0.569; 95% CI, 0.368-0.770). None of the tests were associated with bleeding except for PFA (p < 0.001), with AUC of PFA reaching 0.772 (0.726-0.818).

CONCLUSIONS

Of the three tests assessed, the predictive accuracies of PFA and LTA were satisfying for aspirin secondary prevention, while TEG's performance was poor. Only PFA could provide accurate prognostic information for bleeding.

Prospective, randomised trial of the time dependent antiplatelet effects of 500 mg and 250 mg acetylsalicylic acid i. v. and 300 mg p. o. in ACS (ACUTE)

Little is known about the onset of action after intravenous or oral administration of acetylsalicylic acid (ASA) in patients with acute coronary syndromes (ACS). The aim of the study was to compare intravenous 250 or 500 mg acetylsalicylic acid (ASA) with oral 300 mg in ASA naïve patients with ACS concerning the onset of antiplatelet effects measured by time dependent thromboxane inhibition. A total of 270 patients with ACS < 24 hours were randomised into one of three treatment arms comprising administration of a single dose of ASA as soon as possible after admission. The primary endpoint was platelet inhibition assessed by measurement of arachidonic acid (AA)-induced platelet thromboxane release (TXB₂) 5 minutes (min) after study drug administration. Both 250 mg and 500 mg ASA i. v. inhibited TXB₂ formation nearly completely (geometric means: from 581.7 and 573.9 ng/ml at baseline to 3.9 and 3.1 ng/ml at 5 min, respectively) compared to 300 mg oral ASA (geometric means: from 652.0 to 223.7 ng/ml) (p-value, ANCOVA: < 0.0001). Similar results were obtained for inhibition of AA-induced platelet aggregation (Multiplate ASPItest; from means 86.41 and 85.72 U to 23.04 and 20.57 U at 5 min, respectively) compared to 300 mg oral ASA from mean 87.18 to 75.56 U (p-value, ANCOVA: <0.0001). The rate of bleedings was low and comparable between the groups. In summary, the administration of a single dose of 250 or 500 mg ASA IV compared to 300 mg orally is associated with a faster and more complete inhibition of thromboxane generation and platelet aggregation. Bleeding complications were comparable between the groups.

Aspirin for primary prevention of cardiovascular events: meta-analysis of randomized controlled trials and subgroup analysis by sex and diabetes status

OBJECTIVE

To evaluate the benefits and harms of aspirin for the primary prevention of CVD and determine whether the effects vary by sex and diabetes status.

METHODS

We searched Medline, Embase, and Cochrane databases for randomized controlled trials comparing the effects of aspirin with placebo or control in people with no pre-existing CVD. Two investigators independently extracted data and assessed the study quality. Analyses were performed using Stata version 12.

RESULTS

Fourteen trials (107,686 participants) were eligible. Aspirin was associated with reductions in major cardiovascular events (risk ratio, 0.90; 95% confidence interval, 0.85-0.95), myocardial infarction (0.86; 0.75-0.93), ischemic stroke (0.86; 0.75-0.98) and all-cause mortality (0.94; 0.89-0.99). There were also increases in hemorrhagic stroke (1.34; 1.01-1.79) and major bleeding (1.55; 1.35-1.78) with aspirin. The number needed to treat to prevent 1 major cardiovascular event over a mean follow-up of 6.8 years was 284. By comparison, the numbers needed to harm to cause 1 major bleeding is 299. In subgroup analyses, pooled results demonstrated a reduction in myocardial infarction among men (0.71; 0.59-0.85) and ischemic stroke among women (0.77; 0.63-0.93). Aspirin use was associated with a reduction (0.65; 0.51-0.82) in myocardial infarction among diabetic men. In meta-regression analyses, the results suggested that aspirin therapy might be associated with a decrease in stroke among diabetic women and a decrease in MI among diabetic men and risk reductions achieved with low doses (75 mg/day) were as large as those obtained with higher doses (650 mg/day).

CONCLUSIONS

The use of low-dose aspirin was beneficial for primary prevention of CVD and the decision regarding an aspirin regimen should be made on an individual patient basis. The effects of aspirin therapy varied by sex and diabetes status. A clear benefit of aspirin in the primary prevention of CVD in people with diabetes needs more trials.

Aspirin resistance in systemic lupus erythematosus. A pilot study

Systemic lupus erythematosus (SLE) patients are at increased risk of thrombosis and cardiovascular diseases. Aspirin is an effective treatment option for these patients. The aim of this study was to investigate the presence of aspirin resistance in SLE patients. We studied aspirin resistance in 33 SLE patients and nine healthy controls by using a Multiplate® impedance aggregometer (Dynabyte GmbH, Munich, Germany). Twenty-six SLE patients were on regular aspirin treatment. Aspirin resistance was found in five (19.2%) out of 26 patients who were on aspirin treatment. When the tests were repeated by adding acetylsalicylic acid in the medium, all of these patients became responsive to the aspirin. SLE disease activity, body mass index, smoking status, and the presence of anticardiolipin antibodies or positive lupus anticoagulant test results were no different in patients with or without aspirin resistance. ( p > 0.05 for all). Our results suggest that there may be a considerable number of SLE patients with aspirin resistance.

Primary and secondary prevention of cardiovascular disease in diabetes with aspirin

Diabetes is associated with an increased cardiovascular risk. The role for aspirin in diabetes is of high clinical interest. Guidelines recommend that primary prevention of cardiovascular disease (CVD) in diabetes with aspirin should be based on the individual risk for CVD. New mechanistic studies suggest that enhanced platelet turnover may partly contribute to the fact the primary prevention studies found unequivocal results in diabetes. There is initial evidence that a potential future modification of dosages in diabetes may counteract the enhancement in platelet turnover in diabetes. The use of aspirin in diabetic patients for secondary prevention of CVD is supported by key evidence. The aim of the review is to present recent studies on aspirin for prevention of CVD in diabetes and to highlight its role also in view of new mechanistic and clinical studies with aspirin. Novel aspects of aspirin, e.g. its potential role for the prevention of cancer, are also presented.