Laboratory Aspirin Resistance Reversibility in Diabetic Patients: a Pilot Study Using Different Pharmaceutical Formulations

Aspirin for Primary Cardiovascular Prevention in Patients with Diabetes: Uncertainties and Opportunities

The use of the antiplatelet agent aspirin (acetylsalicylic acid) was previously routinely recommended for the primary prevention of cardiovascular (CV) events in patients with diabetes, but recent large-scale randomized trials have failed to demonstrate a sizeable net clinical benefit with a once-daily, low-dose (81–100 mg) regimen in this population. Previous pharmacokinetic and pharmacodynamic studies have suggested that the aspirin formulation (enteric-coated) and dosing schedule (once daily) studied in randomized trials for primary prevention of CV events defining contemporary clinical practice may not leverage the full potential of the drug, particularly in patients with diabetes. Indeed, the diabetic platelets bear characteristics that increase their thrombotic potential and alter their pharmacologic response to the drug. Consequently, the appropriateness of studying a uniform aspirin regimen in landmark primary prevention trials needs to be revisited. In this review, we present the evidence showing that diabetes not only increases baseline platelet reactivity, but also alters platelet response to aspirin through different mechanisms including a faster platelet turnover rate. Obesity, which is frequently associated with diabetes, also impacts its pharmacokinetics via an increase in distribution volume. Small-scale pharmacokinetic and pharmacodynamic studies have suggested that the relative aspirin resistance phenotype observed in patients with diabetes may be reversed with a twice-daily dosing schedule, and with nonenteric-coated aspirin formulations. Properly powered randomized controlled trials investigating the efficacy and safety of aspirin dosing schedules and formulations tailored to the population of patients with diabetes are urgently required to optimize patient care.

Resistance of aspirin during and after pregnancy: A longitudinal cohort study

OBJECTIVES

The objective of this study is to investigate possible changes in aspirin resistance during and after pregnancy over time.

STUDY DESIGN

A longitudinal cohort study in obstetric high risk women with an indication for aspirin usage during pregnancy to prevent placenta mediated pregnancy complications.

MAIN OUTCOME MEASURES

Aspirin resistance measured in the first, second and third trimester of pregnancy and at least three months postpartum by four complementary test: PFA-200, VerifyNow®, Chronolog light transmission aggregometry (Chronolog LTA) and serum thromboxane B₂ (TxB₂) level measurements. Correlation between the devices was investigated.

RESULTS

In total, 23 pregnant women participated in the present study. Aspirin resistance according to the PFA-200, VerifyNow®, Chronolog LTA and serum TxB₂, was 30.4%, 17.4%, 26.1% and 23.8% respectively. Resistance by any device was 69.6%. Aspirin resistance measured by the VerifyNow®, Chronolog LTA, serum TxB₂ and aspirin resistance by any device during pregnancy was demonstrated more frequently than aspirin resistance after pregnancy. Correlation between the different devices was weak.

CONCLUSION

Aspirin resistance was found in a considerable part of the participants. Considerable variation between participants, within participants over time and between the different devices was found. Prevalence of aspirin resistance during pregnancy differs from after pregnancy. More research on aspirin resistance and clinical obstetric outcome is needed.

New single-nucleotide polymorphisms associated with differences in platelet reactivity and their influence on survival in patients with type 2 diabetes treated with acetylsalicylic acid: an observational study

AIMS

Genetic polymorphisms may contribute to platelet reactivity in diabetic patients; however, the information on their influence on long-term antiplatelet therapy is lacking. Our aim was to evaluate the role of previously described genetic variants and platelet reactivity on risk of all-cause mortality and cardiovascular events.

METHODS

Blood samples were obtained from 303 Caucasian patients. Genome-wide genotyping was performed using Illumina Human Omni 2.5-Quad microarrays, and individual genotyping of selected SNPs was performed using a custom Sequenom iPLEX assay in conjunction with the Mass ARRAY platform. Platelet reactivity was measured with VerifyNow Aspirin Assay and PFA-100 Assay. Univariate and multivariate Cox regression analyses were performed to determine the impact of genetic variants and platelets reactivity on risk of all-cause mortality and cardiovascular events.

RESULTS

Among the 237 patients included in the follow-up, death from any cause occurred in 34 (14.3%) patients and cardiovascular events occurred in 51 (21.5%) patients within a median observation time of 71 months (5.9 years). In univariate analyses, significant association in the presence of minor alleles in TXBA2R (rs1131882) with primary (HR 2.54, 95% CI 1.15-5.60, p = 0.021) and secondary endpoint (HR 2.06, 95% CI 1.06-4.04, p = 0.034) was observed. In addition, multivariate analyses revealed the impact of this polymorphism on primary (HR 2.34, 95% CI 1.09-5.00, p = 0.029) and secondary endpoint (HR 1.89, 95% CI 1.00-3.57, p = 0.048).

CONCLUSIONS

Results of the study demonstrate for the first time an association between genetic polymorphism within TXBA2R gene encoding platelet's surface receptor and long-term survival of diabetic patients treated with ASA.

Post-pregnancy aspirin resistance appears not to be related with recurrent hypertensive disorders of pregnancy

OBJECTIVE

The FRUIT-RCT concluded that low-molecular-weight heparin added to aspirin compared to treatment with aspirin alone is beneficial in the prevention of early-onset hypertensive disorders of pregnancy (HD) in women with inheritable thrombophilia and prior HD and/or a small-for-gestational age (SGA) infant leading to delivery before 34 weeks gestation. The aim of this study is to answer the question whether aspirin resistance is associated with recurrent HD.

STUDY DESIGN

Women with and without recurrent HD matched for age, study arm, and chronic hypertension were invited for this follow-up study 6-16 years after they participated in the FRUIT-RCT. Aspirin resistance was tested after 10days of aspirin intake using three complementary tests: PFA-200, VerifyNow^® and serum thromboxane B₂ (TXB₂). An independent t-test, Mann-Whitney U test, Fisher's Exact test and Chi² test were used for the statistical analyses.

RESULTS

Thirteen of 24 women with recurrent HD and 16 of 24 women without recurrent HD participated. The prevalence of laboratory aspirin resistance was 34.5% according to the PFA-200, 3.4% according to the VerifyNow^® and 24.1% according to TXB₂. The prevalence of aspirin resistance by any test was 51.7%. Aspirin resistance per individual test did not differ between women with and without recurrent HD. Aspirin resistance measured by any test occurred more frequently in women without recurrent HD (p<0.01), irrespective of low-molecular-weight heparin.

CONCLUSIONS

No relation could be demonstrated between recurrent HD and aspirin resistance per test, measured up to 16 years after pregnancy. On the contrary, complementary aspirin resistance measurements were encountered more frequently in women without recurrent HD.