Role of Dipyrone in the High On-Treatment Platelet Reactivity amongst Acetylsalicylic Acid-Treated Patients Undergoing Peripheral Artery Revascularisation

Pharmacology and relevant drug interactions of metamizole

Metamizole is a frequently prescribed analgesic because of its favourable benefit/risk ratio compared with classic NSAIDs. However, increasing research shows that metamizole displays several drug interactions that are relevant to clinical practice. We reviewed the literature to summarize the pharmacology and most clinically relevant drug interactions of metamizole. Metamizole has a fast analgesic effect but a short half-life and duration of action. The exact mechanism of action of metamizole is currently not fully known. Studies showed that metamizole appears to be a moderate to strong inductor of the enzymes CYP3A4, CYP2B6 and CYP2C19; a weak inductor of CYP2C9; and a moderate inhibitor of CYP1A2. Furthermore, metamizole inhibits the effect of acetylsalicylic acid when taken simultaneously. Metamizole should be cautiously used together with other drugs that can cause agranulocytosis. If metamizole is prescribed in a high dosage (1000 mg three or four times daily) for more than 1 day, these pharmacokinetic and dynamic interactions should be taken into account.

High on-treatment platelet reactivity in peripheral arterial disease: A systematic review

OBJECTIVES

To highlight current evidence pertaining to the measurement methods and prevalence of high on-treatment platelet reactivity (HTPR) in patients with PAD, as well as to evaluate the relationship between HTPR and recurrent adverse cardiovascular and limb events in PAD patients.

METHODS

A systematic review of English-language literature on HTPR in patients with PAD. An electronic literature search of PubMed and Medline was performed in May 2021.

RESULTS

A total of 29 studies with a total number of 11,201 patients with PAD were identified. HTPR during clopidogrel treatment ranges from 9.8 to 77%, and during aspirin treatment ranges from 4.1 to 50% of PAD patients. HTPR was associated with adverse clinical outcomes. The need for limb revascularisation was higher in patients with HTPR during clopidogrel use. Similarly, HTPR during aspirin use in the PAD population was predictive of adverse cardiovascular events (HR 3.73; 95% CI, 1.43-9.81; p = .007). A wide range of techniques were applied to measure platelet resistance, without consensus on cut-off values. Furthermore, differing patient populations, a variety of antiplatelet regimens, and differing clinical endpoints highlight the high degree of heterogeneity in the studies included in this review.

CONCLUSION

No consensus on technique or cut-off values for HTPR testing has been reached. Patients with HTPR are potentially at a greater risk of adverse limb-related and cardiovascular events than patients sensitive to antiplatelet therapy illustrating the need for clinical implementation of HTPR testing. Future research must aim for consistent methodology. Adaptation of antiplatelet therapy based on HTPR results requires further exploration.

Monitoring antiplatelet therapy: where are we now?

Single antiplatelet therapy represents the cornerstone of thrombosis prevention in atherosclerotic cardiovascular disease. Dual antiplatelet therapy (DAPT), consisting of aspirin plus a P2Y 12 inhibitor, is the standard of care for patients with acute coronary syndrome or undergoing both coronary and peripheral percutaneous interventions. Recent data suggest the efficacy of DAPT also after minor stroke. In this setting, a large body of evidence has documented that genetic and acquired patients' characteristics may affect the magnitude of platelet inhibition induced by antiplatelet agents. The implementation of tools allowing the identification and prediction of platelet inhibition has recently been shown to improve outcomes, leading to an optimal balance between antithrombotic efficacy and bleeding risk. We are therefore clearly moving towards tailored antiplatelet therapy. The aim of this paper is to summarize the available evidence on the evaluation of platelet inhibition in patients with coronary, peripheral, or cerebrovascular atherosclerosis. We will here focus on antiplatelet therapy based on both aspirin and P2Y 12 inhibitors. In addition, we provide practical insights into the clinical settings in which it appears reasonable to implement antiplatelet therapy monitoring.

Predicting Arterial Thrombotic Events Following Peripheral Revascularization Using Objective Viscoelastic Data

Background Peripheral artery disease is endemic in our globally aging population, with >200 million affected worldwide. Graft/stent thrombosis after revascularization is common and frequently results in amputation, major adverse cardiovascular events, and cardiovascular mortality. Optimizing medications to decrease thrombosis is of paramount importance; however, limited guidance exists on how to use and monitor antithrombotic therapy in this heterogeneous population. Thromboelastography with platelet mapping (TEG-PM) provides comprehensive coagulation metrics and may be integral to the next stage of patient-centered thrombophrophylaxis. This prospective study aimed to determine if TEG-PM could predict subacute graft/stent thrombosis following lower extremity revascularization, and if objective cut point values could be established to identify those high-risk patients. Methods and Results We conducted a single-center prospective observational study of patients undergoing lower extremity revascularization. Patients were followed up for the composite end point postoperative graft/stent thrombosis at 1 year. TEG-PM analysis of the time point before thrombosis in the event group was compared with the last postoperative visit in the nonevent group. Cox proportional hazards analysis examined the association of TEG-PM metrics to thrombosis. Cut point analysis explored the predictive capacity of TEG-PM metrics for those at high risk. A total of 162 patients were analyzed, of whom 30 (18.5%) experienced graft/stent thrombosis. Patients with thrombosis had significantly greater platelet aggregation (79.7±15.7 versus 58.5±26.4) and lower platelet inhibition (20.7±15.6% versus 41.1±26.6%) (all P<0.01). Cox proportional hazards analysis revealed that for every 1% increase in platelet aggregation, the hazard of experiencing an event during the study period increased by 5% (hazard ratio, 1.05 [95% CI, 1.02-1.07]; P<0.01). An optimal cut point of >70.8% platelet aggregation and/or <29.2% platelet inhibition identifies those at high risk of thrombosis with 87% sensitivity and 70% to 71% specificity. Conclusions Among patients undergoing lower extremity revascularization, increased platelet reactivity was predictive of subacute postoperative graft/stent thrombosis. On the basis of the cut points of >70.8% platelet aggregation and <29.2% platelet inhibition, consideration of an alternative or augmented antithrombotic regimen for high-risk patients may decrease the risk of postoperative thrombotic events.

Platelet reactivity testing in peripheral artery disease

DISCLAIMER

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PURPOSE

Oral antiplatelet therapy is routinely used to prevent adverse cardiovascular events in patients with peripheral artery disease (PAD). Several laboratory tests are available to quantify the degree of platelet inhibition following antiplatelet therapy. This article aims to provide a review of the literature surrounding platelet functional testing in patients with PAD receiving oral P2Y12 inhibitors and to offer guidance to clinicians for the use and interpretation of these tests.

SUMMARY

A literature search of PubMed and the Web of Science Core Collection database was conducted. All studies that performed platelet function testing and reported clinical outcomes in patients with PAD were included. Evaluation of the data suggests that, among the available testing strategies, the VerifyNow platelet reactivity unit (PRU) test is the most widely used. Despite numerous investigations attempting to define a laboratory threshold indicating suboptimal response to antiplatelet therapy, controversy exists about which PRU value best correlates with cardiovascular outcomes (ie, mortality, stent thrombosis, etc). In the PAD literature, the most commonly used PRU thresholds are 208 or higher and 235 or higher. Nonetheless, adjusting antiplatelet regimens based on suboptimal P2Y12 reactivity values has yet to be proven useful in reducing the incidence of adverse cardiovascular outcomes. This review examines platelet function testing in patients with PAD and discusses the interpretation and application of these tests when monitoring the safety and efficacy of P2Y12 inhibitors.

CONCLUSION

Although platelet functional tests may be simple to use, clinical trials thus far have failed to show benefit from therapy adjustments based on test results. Clinicians should be cautioned against relying on this test result alone and should instead consider a combination of laboratory, clinical, and patient-specific factors when adjusting P2Y12 inhibitor therapy in clinical practice.

Impact of high on-treatment platelet reactivity after angioplasty in patients with critical limb ischemia

OBJECTIVES

Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel is standard of care in patients with peripheral artery disease (PAD) after percutaneous transluminal angioplasty (PTA). However, high on treatment platelet reactivity (HTPR) to DAPT is frequent and associated with major adverse limb events (MALE) in PAD patients. Nevertheless, association of MALE and HTPR in patients with critical limb ischemia (CLI) is not known. Moreover, comorbidities might confound response to antiplatelet medication further. Hence, in this trial we analyzed pharmacodynamic responses to DAPT and clinical events in CLI patients post PTA.

METHODS

In this prospective single center pilot analysis, we included 71 CLI patients. Patients received DAPT after PTA. Antiplatelet effect were measured by light transmission aggregometry (LTA) and vasodilator-stimulated protein phosphorylation assay (VASP). MALE, major adverse cardiac and cerebrovascular events (MACCE) and BARC bleeding within 12 months follow-up were assessed.

RESULTS

Mean age of patients was 73.37 ± 7.36 years and 47 (66.2%) were male. Overall HTPR appeared in 46 patients (64.8%). MALE and MACCE showed no differences between patients with and patients without HTPR. However, bleeding was higher in patients with sufficient pharmacodynamic response to DAPT (Bleeding - HTPR: 13.4% vs. no HTPR: 36.0%; log-rank HR: 0.32; 95% CI 0.1079 to 0.9396 p = 0.0217). This finding remained robust in multivariate analysis.

CONCLUSION

HTPR to DAPT is frequent in CLI patients. However, bleeding was higher in patients with sufficient response to DAPT. Ischemic events did not differ. Hence, CLI patients might benefit from an alternative antithrombotic approach.

Intake of aspirin prior to metamizole does not completely prevent high on treatment platelet reactivity

PURPOSE

Metamizole can sterically inhibit aspirin (ASA) from binding to cyclooxygenase 1 (COX1). It is recommended that ASA should be taken 30 min prior to metamizole to maintain the irreversible inhibition of arachidonic acid (AA)-induced platelet aggregation. We aimed to analyse the inhibitory effect of ASA and metamizole on AA-induced platelet aggregation over the course of the day.

METHODS

We analysed hospitalized patients who ingested ASA at least 30 min prior to metamizole (recommended dosing group, n = 15), metamizole prior or simultaneously with ASA (not recommended dosing group, n = 16) and patients with unknown or mixed intake (mixed dosing group, n = 5). AA-induced light transmission (LTA) and impedance aggregometry (IA) were measured before, 1-2 and 5-6 h after the intake of ASA ± metamizole.

RESULTS

Maximum AA-induced LTA prior to the intake of ASA was significantly lower and the rate of high on treatment platelet reactivity (HTPR) higher in the recommended compared with the not recommended dosing group (19.6% vs. 46.9%, p = 0.011 and 4/15 vs. 12/16 patients, p = 0.017). There was no difference when IA was used. Maximum AA-induced LTA after the intake of ASA ± metamizole was lower in patients in the not recommended but not in the recommended dosing group. All patients with HTPR in the recommended dosing group had regular inhibition of AA-induced LTA after discontinuation of metamizole.

CONCLUSION

Co-medication of ASA and metamizole significantly influences platelet inhibition with variations during the day and can cause HTPR in patients taking ASA prior to metamizole or simultaneously.

Effect of platelet count on long-term prognosis of cerebral infarction

OBJECTIVE

This study aimed to analyze the correlation between platelet (PLT) count and the modified Rankin scale (mRS) in patients with cerebral infarction (CI) at the later stage of rehabilitation, which can be used to guide the secondary prevention strategy of CI.

METHODS

A total of 180 CI patients were divided into three groups according to PLT count: low PLT group (<125×109/L), medium PLT group (126- 225×109/L) and high PLT group (>226×109/L). The mRS was evaluated after three months and one year, respectively, and the difference in long-term prognosis between groups was analyzed. The mRS is an ordered scale coded from 0 (no symptoms at all) through 5 (severe disability) 6 (death).

RESULTS

Finally, a total of 99 patients had complete data. The results of the multiple comparisons among the three groups were as follows: the analysis of variance of the mRS at three months after onset yielded F = 6.714 and P = 0.002, and the difference was statistically significant. The mRS was lowest in the medium PLT group (2.09±1.465), and neurological function recovery was the best. After one year, the mRS for the medium PLT group was the lowest (1.49±1.523), with F = 6.860 and P = 0.002. The repeated measures analysis of variance revealed that the effect of continuous rehabilitation was significant in the interval from three months to one year after onset (F = 35.528, P < 0.001). This was very significant, especially for patients taking aspirin (F = 50.908, P < 0.001). However, for patients who did not take aspirin, the effect of continuous rehabilitation was not obvious during the nine months, and the difference between the results of two mRS measurements was not statistically significant (F = 1.089, P = 0.308).

CONCLUSIONS

Patients with a PLT count of 126- 225×109/L had the lowest mRS between three months and one year after onset, but had the best recovery of nerve function. Patients who persisted in taking aspirin continued to significantly recover during the 9-month period, from three months to one year after onset. Aspirin is not only a secondary preventive drug, but also an important drug to promote the rehabilitation of CI patients.

Metamizole inhibits arachidonic acid-induced platelet aggregation after surgery and impairs the effect of aspirin in hospitalized patients

PURPOSE

The inhibitory effect of metamizole on platelet aggregation is known for several years, but most studies were conducted in healthy volunteers with contradictory results. Recent studies have shown an inhibitory effect of metamizole on acetylsalicylic acid (ASA)-induced platelet aggregation. We aimed to investigate the effect of metamizole on platelet aggregation after an elective surgery and the effect of metamizole on ASA-induced platelet aggregation in hospitalized patients.

METHODS

We performed platelet aggregation analysis after induction with ADP, arachidonic acid (AA), epinephrine, and collagen in 37 patients prior to an elective visceral or thoracic surgery and on postoperative day (POD) 1 and POD 3 1-2 h and 5-6 h after metamizole. In another cohort of 10 hospitalized patients receiving the combination of metamizole and ASA for more than 7 days, AA-induced platelet aggregation was analyzed in the morning prior to the intake of both drugs.

RESULTS

Metamizole induced a strong inhibitory effect on AA-induced platelet aggregation at all time points being detectable up to 41 h in some patients. Besides a less pronounced effect on collagen-induced platelet aggregation on POD 3 1-2 h after metamizole, all other inductors showed no effect. In 4 out of 10 hospitalized patients, no ASA-induced inhibition of platelet aggregation was detectable without correlation to sequence of administration.

CONCLUSIONS

The reason why some patients have a long-lasting inhibitory effect of metamizole on COX-induced platelet aggregation that might interfere with ASA should be investigated in a larger cohort of patients.