Serum Thromboxane B2 Research Articles

Reduced Antiplatelet Effect of Aspirin Does Not Predict Cardiovascular Events in Patients With Stable Coronary Artery Disease.

BackgroundIncreased platelet aggregation during antiplatelet therapy may predict cardiovascular events in patients with coronary artery disease. The majority of these patients receive aspirin monotherapy. We aimed to investigate whether high platelet‐aggregation levels predict cardiovascular events in stable coronary artery disease patients treated with aspirin.Methods and ResultsWe included 900 stable coronary artery disease patients with either previous myocardial infarction, type 2 diabetes mellitus, or both. All patients received single antithrombotic therapy with 75 mg aspirin daily. Platelet aggregation was evaluated 1 hour after aspirin intake using the VerifyNow Aspirin Assay (Accriva Diagnostics) and Multiplate Analyzer (Roche; agonists: arachidonic acid and collagen). Adherence to aspirin was confirmed by serum thromboxane B2. The primary end point was the composite of nonfatal myocardial infarction, ischemic stroke, and cardiovascular death. At 3‐year follow‐up, 78 primary end points were registered. The primary end point did not occur more frequently in patients with high platelet‐aggregation levels (first versus fourth quartile) assessed by VerifyNow (hazard ratio: 0.5 [95% CI, 0.3–1.1], P=0.08) or Multiplate using arachidonic acid (hazard ratio: 1.0 [95% CI, 0.5–2.1], P=0.92) or collagen (hazard ratio: 1.4 [95% CI, 0.7–2.8], P=0.38). Similar results were found for the composite secondary end point (nonfatal myocardial infarction, ischemic stroke, stent thrombosis, and all‐cause death) and the single end points. Thromboxane B2 levels did not predict any end points. Renal insufficiency was the only clinical risk factor predicting the primary and secondary end points.ConclusionsThis study is the largest to investigate platelet aggregation in stable coronary artery disease patients receiving aspirin as single antithrombotic therapy. We found that high platelet‐aggregation levels did not predict cardiovascular events.

On-pump Cardiac Surgery Enhances Platelet Renewal and Impairs Aspirin Pharmacodynamics: Effects of Improved Dosing Regimens.

On-pump cardiac surgery may trigger inflammation and accelerate platelet cyclooxygenase-1 renewal, thereby modifying low-dose aspirin pharmacodynamics. Thirty-seven patients on standard aspirin 100 mg once-daily were studied before surgery and randomized within 36 hours postsurgery to 100 mg once-daily, 100 mg twice-daily, or 200 mg once-daily for 90 days. On day 7 postsurgery, immature and mature platelets, platelet mass, thrombopoietin, glycocalicin, leukocytes, C-reactive protein, and interleukin-6 significantly increased. Interleukin-6 significantly correlated with immature platelets. At day 7, patients randomized to 100 mg once-daily showed a significant increase in serum thromboxane (TX)B2 within the 24-hour dosing interval and urinary TXA2 metabolite (TXM) excretion. Aspirin 100 mg twice-daily lowered serum TXB2 and prevented postsurgery TXM increase (P < 0.01), without affecting prostacyclin metabolite excretion. After cardiac surgery, shortening the dosing interval, but not doubling the once-daily dose, rescues the impaired antiplatelet effect of low-dose aspirin and prevents platelet activation associated with acute inflammation and enhanced platelet turnover.

Acetylsalicylic acid in critically ill patients: a cross-sectional and a randomized trial.

BackgroundDespite decades of clinical use, the pharmacokinetics and the effects of acetylsalicylic acid (ASA) in critically ill patients remain ill‐defined. We aimed to investigate the pharmacokinetics and the effects of different ASA formulations during critical illness.DesignA cross‐sectional study and a randomized, parallel‐group trial were performed. Critically ill patients under chronic oral ASA treatment (100 mg enteric‐coated) were screened for high ‘on‐treatment’ platelet reactivity (HTPR) according to arachidonic acid‐induced whole‐blood aggregometry. Thirty patients with HTPR were randomized to receive 100 mg ASA intravenously, 100 mg enteric‐coated ASA bid (bis in die) or 81 mg chewable ASA (n = 10 per group). Serum thromboxane B2 (TXB2) levels, ASA and salicylic acid levels were quantified.ResultsOf 66 patients, 85% (95% confidence intervals 74–93%) had HTPR. Compared to baseline infusion of 100 mg, ASA significantly reduced platelet aggregation after 24 h to median 80% (Quartiles: 66–84%). Intake of 81 mg chewable ASA significantly reduced platelet aggregation to 75% (54–86%) after four hours, but increased it to 117% after 24 h (81–163%). Treatment with 100 mg enteric‐coated ASA bid decreased platelet aggregation after 24 h to median 56% (52–113%). Baseline TXB2 levels were median 0·35 ng/mL (0·07–0·94). Infusion of ASA or intake of 100 mg ASA bid reduced TXB2 levels to 0·07–0·18 ng/mL after 24 h, respectively. Chewable ASA reduced TXB2 levels only transiently. Pharmacokinetic analysis revealed highly variable absorption patterns of oral ASA formulations.ConclusionThere is a very high prevalence of HTPR in critically ill patients on peroral ASA therapy, caused by an incomplete suppression of TXB2 and/or by impaired absorption of ASA.

In Silico Modeling of the Antiplatelet Pharmacodynamics of Low-dose Aspirin in Health and Disease.

The influence of platelet turnover on cyclooxygenase (COX-1) inhibition by low-dose aspirin remains largely uncharacterized due to limited feasibility of studying aspirin pharmacodynamics in bone marrow precursors. We developed an in silico compartmental model describing the aspirin effects on COX-1 activity in a population of megakaryocytes (MK) and in peripheral platelets. Model parameters were inferred from the literature and calibrated using measurements of serum thromboxane B2 (sTXB2 ), as proxy of COX-1 activity in peripheral platelets, in 17 healthy subjects and 24 patients with essential thrombocythemia (ET). The model reproduced well the average time-course of sTXB2 inhibition in healthy (accuracy = 10.4%), the reduced inhibition of sTXB2 observed in ET, and the effect of different dosing regimens. In conclusion, the in silico model accurately describes COX-1 inactivation by low-dose aspirin in MK and platelets in different clinical settings, and might help personalize aspirin regimens in conditions of altered megakaryopoiesis.

Once versus twice daily aspirin after coronary bypass surgery: a randomized trial

Background Acetyl-salicylic acid (ASA) hyporesponsiveness occurs transiently after coronary artery bypass graft (CABG) surgery and may compromise the effectiveness of ASA in reducing thrombotic graft failure. A reduced response to ASA 81 mg once-daily after CABG surgery is overcome by four times daily ASA dosing. Objectives To determine whether ASA 325 mg once-daily or 162 mg twice-daily overcomes a reduced response to ASA 81 mg once-daily after CABG surgery. Methods Adults undergoing CABG surgery were randomized to ASA 81 mg once-daily, 325 mg once-daily or 162 mg twice-daily. The primary outcome was median serum thromboxane B2 (TXB2 ) level on postoperative day 4. We pooled the results with those of our earlier study to obtain better estimates of the effect of ASA 325 mg once-daily or in divided doses over 24 h. Results We randomized 68 patients undergoing CABG surgery. On postoperative day 4, patients randomized to receive ASA 81 mg once-daily had a median day 4 TXB2 level of 4.2 ng mL-1 (Q1, Q3: 1.5, 7.5 ng mL-1 ), which was higher than in those randomized to ASA 162 mg twice-daily (1.1 ng mL-1 ; Q1, Q3: 0.7, 2.7 ng mL-1 ) and similar to those randomized to ASA 325 mg once-daily (1.9 ng mL-1 ; Q1, Q3: 0.9, 4.7 ng mL-1 ). Pooled data showed that the median TXB2 level on day 4 in groups receiving ASA 162 mg twice-daily or 81 mg four times daily was 1.1 ng mL-1 compared with 2.2 ng mL-1 in those receiving ASA 325 mg once-daily. Conclusions Multiple daily dosing of ASA is more effective than ASA 81 mg once-daily or 325 mg once-daily at suppressing serum TXB2 formation after CABG surgery. A twice-daily treatment regimen needs to be tested in a clinical outcome study.

Thrombopoietin and platelet aggregation in patients with stable coronary artery disease

Thrombopoietin (TPO) may facilitate platelet activation and aggregation. However, data on the impact of TPO on platelet aggregation in patients with stable coronary artery disease (CAD) are scarce. We aimed to investigate associations between TPO and platelet aggregation and activation in patients with stable coronary artery disease (CAD). We studied 900 stable CAD patients. Serum TPO was assessed by ELISA. Platelet aggregation was evaluated using the Multiplate Analyzer (agonists: arachidonic acid [AA] and collagen) and the VerifyNow Aspirin Assay. Platelet activation was evaluated by soluble (s)P-selectin. Cyclooxygenase-1 inhibition was evaluated by serum thromboxane B2 (TXB2). We found that TPO correlated weakly with platelet aggregation evaluated by Multiplate using AA (r = −0.09, p = 0.01) and collagen as agonists (r = −0.03, p = 0.43) and by VerifyNow (r = 0.07, p = 0.03). We found no correlation between TPO and sP-selectin (r = −0.01, p = 0.70). Independent predictors of AA-induced platelet aggregation by Multiplate included high levels of sP-selectin and serum TXB2, high platelet count, increasing age and body mass index, female sex, and active smoking. Independent predictors of TPO included low AA-induced platelet aggregation by Multiplate, high levels of hs-CRP, active smoking, and high platelet aggregation evaluated by VerifyNow. In conclusion, TPO levels did not correlate with platelet activation and only weak associations were found between TPO and platelet aggregation, suggesting that TPO did not substantially facilitate platelet aggregation in stable CAD patients.

Enteric Coating and Aspirin Nonresponsiveness in Patients With Type 2 Diabetes Mellitus

BackgroundA limitation of aspirin is that some patients, particularly those with diabetes, may not have an optimal antiplatelet effect. ObjectivesThe goal of this study was to determine if oral bioavailability mediates nonresponsiveness. MethodsThe rate and extent of serum thromboxane generation and aspirin pharmacokinetics were measured in 40 patients with diabetes in a randomized, single-blind, triple-crossover study. Patients were exposed to three 325-mg aspirin formulations: plain aspirin, PL2200 (a modified-release lipid-based aspirin), and a delayed-release enteric-coated (EC) aspirin. Onset of antiplatelet activity was determined by the rate and extent of inhibition of serum thromboxane B2 (TXB2) generation. Aspirin nonresponsiveness was defined as a level of residual serum TXB2 associated with elevated thrombotic risk (<99.0% inhibition or TXB2 >3.1 ng/ml) within 72 h after 3 daily aspirin doses. ResultsThe rate of aspirin nonresponsiveness was 15.8%, 8.1%, and 52.8% for plain aspirin, PL2200, and EC aspirin, respectively (p < 0.001 for both comparisons vs. EC aspirin; p = 0.30 for comparison between plain aspirin and PL2200). Similarly, 56% of EC aspirin–treated subjects had serum TXB2 levels >3.1 ng/ml, compared with 18% and 11% of subjects after administration of plain aspirin and PL2200 (p < 0.0001). Compared with findings for plain aspirin and PL2200, this high rate of nonresponsiveness with EC aspirin was associated with lower exposure to acetylsalicylic acid (63% and 70% lower geometric mean maximum plasma concentration [Cmax] and 77% and 82% lower AUC0–t [area under the curve from time 0 to the last time measured]) and 66% and 72% lower maximum decrease of TXB2, with marked interindividual variability. ConclusionsA high proportion of patients treated with EC aspirin failed to achieve complete inhibition of TXB2 generation due to incomplete absorption. Reduced bioavailability may contribute to “aspirin resistance” in patients with diabetes. (Pharmacodynamic Evaluation of PL2200 Versus Enteric-Coated and Immediate Release Aspirin in Diabetic Patients; NCT01515657)

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

ObjectiveThe 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 designWomen 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. ResultsThirteen 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. ConclusionsNo 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.

Platelet function one and three months after coronary bypass surgery in relation to once or twice daily dosing of acetylsalicylic acid

IntroductionCurrent guidelines recommend acetylsalicylic acid (ASA) treatment after coronary artery bypass grafting (CABG) to reduce thrombotic vein graft occlusion. The optimal dosage of ASA is not known. Materials and methodsForty-two patients undergoing elective CABG were randomized to receive either ASA 75mg or 160mg once daily (OD) or 75mg twice daily (BID) after the operation. Platelet function testing was performed before, and one and three months after the operation. ResultsWhite blood cell counts increased during the initial postoperative days whereas platelet counts were initially slightly reduced after the operation but increased after one month without any major changes of mean platelet volumes. Serum thromboxane B2 was more effectively suppressed at one and three months after the operation with ASA 75mg BID or 160mg OD than with 75mg OD (p<0.001). ASA 75mg BID and 160mg OD were equally effective. Adenosine diphosphate stimulated platelet aggregation in whole blood (Multiplate®) was increased one and three months after the operation, and this was counteracted by ASA 75mg BID but not by 75 or 160mg OD. Arachidonic acid-induced aggregation was more effectively inhibited by 75mg BID or 160mg OD compared to 75mg OD at three months. ConclusionsLess effective inhibition of platelet activation was obtained with ASA 75mg OD than with ASA 160mg OD or 75mg BID up to three months after CABG. Especially the latter dose is of interest for further studies of efficacy and clinical outcomes after CABG.

Effects of applying ulinastatin in donors and recipients on the renal function of recipients in the living donor renal transplantation and the mechanism of renal protection

Objective To investigate the effects of ulinastatin(UTI) on renal function and the mechanism of renal protection, when using UTI in donors and recipients in living donor renal transplantation. Methods Forty pairs of patients were randomly assigned into two groups: the ulinastatin group(group U) and the control group(group C). One hour before blocking renal artery, the donors in group U were given ulinastatin 500 U/kg (dissolved in 50 ml saline) for 20 min by intravenous pump, when the renal blood vessels opening, the recipients in group U were infused ulinastatin 500 U/kg (dissolved in 50 ml saline) for 20 min. The donors and recipients in group C received 50 ml saline solution in the same way. The serum thromboxane B2(TXB2), 6-ketone-prostaglandin F1α(6-keto-PGF1α) levels and the TXB2/6-keto-PGF1α were compared before anesthesia induction(T1), 15 min before vessels opening(T2), vessels opening immediately(T3), the end of the operation(T4), 6 h after surgery (T5), 24 h after surgery (T6) in two groups. The serum creatinine(Scr) and cystatin C(CysC) levels were detected and urine volume was recorded at T1, T6 and 48 h after surgery (T7). Results Compared with T1, the serum TXB2 levels in two group were significantly increased at the time points of T2-T6(P 0.05). Conclusions UTI can protect renal function during related donor kidney transplantation, which is related to effectively correct the TXA2/PGI2 proportional unbalance to improve renal blood perfusion. Key words: Living donor renal transplantation; Ulinastatin; Thromboxane A2; Prostacyclin I2; Ischemia/reperfusion injury

Effects of Firocoxib, Flunixin Meglumine, and Phenylbutazone on Platelet Function and Thromboxane Synthesis in Healthy Horses.

Determine the effects of nonsteroidal anti-inflammatory drugs (NSAID) on platelet function and thromboxane synthesis immediately after drug administration and following 5 days of NSAID administration in healthy horses. Randomized cross-over study. Healthy adult horses (n=9; 6 geldings and 3 mares). Horses received either flunixin meglumine (1.1 mg/kg IV every 12 hours), phenylbutazone (2.2 mg/kg IV every 12 hours), or firocoxib (loading dose of 0.27 mg/kg IV on day 1, then 0.09 mg/kg IV every 24 hours for 4 days) for a total of 5 days. Blood samples were collected prior to drug administration (day 0), 1 hour after initial NSAID administration (day 1), and then 1 hour post-NSAID administration on day 5. Platelet function was assessed using turbidimetric aggregometry and a platelet function analyzer. Serum thromboxane B2 concentrations were determined by commercial ELISA kit. A minimum 14 day washout period occurred between trials. At 1 hour and 5 days postadministration of firocoxib, flunixin meglumine, or phenylbutazone, there was no significant effect on platelet aggregation or function using turbidimetric aggregometry or a platelet function analyzer. There was, however, a significant decrease in thromboxane synthesis at 1 hour and 5 days postadministration of flunixin meglumine and phenylbutazone that was not seen with firocoxib. Preoperative administration of flunixin meglumine, phenylbutazone, or firocoxib should not inhibit platelet function based on our model. The clinical implications of decreased thromboxane B2 synthesis following flunixin meglumine and phenylbutazone administration are undetermined.

Antiplatelet Effect Durability of a Novel, 24-Hour, Extended-Release Prescription Formulation of Acetylsalicylic Acid in Patients With Type 2 Diabetes Mellitus

High platelet reactivity and high platelet turnover have been implicated in incomplete platelet inhibition during immediate-release acetylsalicylic acid therapy in patients with type 2 diabetes mellitus (DM). An extended-release acetylsalicylic acid (ER-ASA; Durlaza) formulation was developed to provide 24-hour antithrombotic effects with once-daily dosing. The objective of the study was to evaluate the antiplatelet effects of ER-ASA in patients with DM. In this open-label, single-center study, patients with DM (n= 40) and multiple cardiovascular risk factors received ER-ASA 162.5mg/day for 14 ± 4days. Multiple platelet function tests, serum and urinary thromboxane B2 metabolites, prostacyclin metabolite, and high-sensitive C-reactive protein levels were assessed at 1, 12, 16, and 24hours post-dose. Patients with high platelet turnover and/or high platelet reactivity were treated with ER-ASA 325mg/day for 14 ± 4days, and laboratory analyses were repeated. All patients responded to ER-ASA 162.5mg/day as measured by arachidonic acid-induced aggregation, and there was no loss of the platelet inhibitory effect of ER-ASA 162.5mg/day over 24hours post-dose (p= not significant). The antiplatelet effect was sustained over 24hours for all platelet function measurements. Mean 1- to 24-hour serum thromboxane B2 levels were low with both doses and were lower with ER-ASA 325mg/day compared with 162.5mg/day therapy (p= 0.002). In conclusion, ER-ASA 162.5mg daily dose provided sustained antiplatelet effects over 24hours in patients with type 2 DM and multiple cardiovascular risk factors and had a favorable tolerability profile.

The monitoring of antiaggregation effect of acetylsalicylic acid therapy by measuring serum thromboxane B2 in patients with coronary artery bypass grafting.

Cardiovascular patients take acetylsalicylic acid (ASA) for preventing myocardial infarction and other thromboembolic complications. It is already known that in some patients this therapy is not effective. The aim of this study was to assess the percentage of ASA resistance on the sample of patients with coronary artery bypass grafting. Our study included 105 patients with coronary artery bypass grafting treated with ASA 150 mg/day or lesser. Platelet aggregation was measured by serum thromboxane B2 level as well as impedance aggregometry from whole blood to determine ASA antiaggregation effect. The percentage of ASA resistance was 41.9% with impedance aggregometry, and after determining the serum thromboxane B2 level this percentage was only 8.6%. The correlation between these two methods was weak (r = 0.443; P < 0.0001). Thromboembolic complications still occur in ASA-treated patients because some patients are resistant to ASA therapy. It would be useful to monitor the effectiveness of ASA therapy and give another antiaggregation drug to these patients to reduce adverse events. The problem is which test is ideal because different tests show different percentages of ASA resistance.

High platelet reactivity on aspirin in patients with acute ST elevation myocardial infarction

BackgroundDespite dual antiplatelet treatment, major ischemic events are common following ST elevation myocardial infarction (STEMI). We aimed to assess high platelet reactivity on aspirin (HPR-aspirin) and its association with P2Y12i (HPR-P2Y12i) during the acute phase of STEMI. MethodsWe included all consecutive patients admitted for STEMI treated by primary angioplasty in our center for 1year. All patients received a loading dose followed by a maintenance dose of aspirin (75mg/day) and prasugrel (ticagrelor or clopidogrel if contraindicated). Platelet reactivity was assessed 4±1days and 75±15days after admission using light transmission aggregometry with arachidonic acid (LTA-AA–HPR-aspirin) and VASP (HPR-P2Y12i) to define HPR as well as serum Thromboxane-B2 and LTA-ADP. Major cardiac and cerebrovascular events were recorded for 1year. ResultsWe included 106 patients – mean age was 61y.o., 76% were male and 20% had diabetes. STEMI was anterior in 52% and LV ejection fraction at discharge was 51±9%. 50% of patients were treated with prasugrel and 34% with ticagrelor. At day 4 after STEMI, HPR-aspirin was found in 26% patients and HPR-P2Y12i in 7%. HPR- both aspirin and P2Y12i was found in 4%. Diabetes and age were predictors of HPR-aspirin. HPR-aspirin was persistent 75days later in 36% patients. At 1year, 7.9% patients had experienced major adverse cardiovascular and cerebrovascular events (MACCE). HPR-aspirin and HPR on both aspirin and P2Y12i were significantly associated with MACCE. ConclusionHPR-aspirin is frequent just after STEMI and associated with MACCE especially when associated with HPR-P2Y12i.

0053 : Naproxen as an alternative to aspirin for platelet inhibition in patients with cardiovascular disease requiring nonsteroidal anti-inflammatory drug?

Concomitant prescription of non-steroidal anti-inflammatory drugs (NSAIDs) and low dose aspirin is not recommended due to competitive interaction with cyclooxygenase-1 and higher risk of gastrotoxicity. To assess the efficacy of naproxen over time as antiplatelet agent. We included 14 healthy volunteers. We first evaluated naproxen effiacy by performing aggregation tests: light transmission aggregometry with arachidonic acid (LTA-AA), platelet function analyzer-100 with epinephrine cartridge (PFA-EPI) and serum thromboxane B2 (TXB2) measurement at baseline (T0), 2 hours (T2), 12 hours (T12), 24 hours (T24) and 48 hours (T48) after receiving one single dose of naproxen 550mg and then at T24 and T48 after a twice daily dose of naproxen 550mg for three days. We then compared the peak of efficacy two hours after naproxen with ibuprofen 400mg and aspirin 75mg and tested the switch back from NSAIDs to aspirin. Platelet aggregation (LTA-AA) after one dose of naproxen was inhibited at T2 and T12 and 50% of volunteers recovered at T24 and 93% at T48. Similar results were found with serum TXB2 concentration and PFA-EPI and multiple doses of naproxen. After naproxen at T2, maximal aggregation intensity (MAI) was 4% [1%-16%], PFA EPI 260s [88s-300s], TXB2 inhibition 98% [89-99%]. After aspirin, MAI was 5% [0%-69%], PFA-EPI was 214s [103s-300s] and TXB2 inhibition 98% [91%-98%]. After ibuprofen, MAI was 2% [1%-4%], PFA EPI 211s [111s-300s] and TXB2 inhibition 94% [92-94%]. After a 48h interruption of NSAIDs with a verified recovery of platelet aggregation, aspirin did not inhibit platelet aggregation for 83% and 50% of subjects who took naproxen and ibuprofen. Naproxen has a stable biological antiplatelet effect similar to aspirin. However, after naproxen or ibuprofen, aspirin was unable to inhibit platelet aggregation. These results suggest than NSAIDs could block the action of aspirin on platelets for several days. The author hereby declares no conflict of interest

Platelet Inhibition With Ticagrelor 60 mg Versus 90 mg Twice Daily in the PEGASUS-TIMI 54 Trial

BackgroundThe PEGASUS-TIMI 54 (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin–Thrombolysis In Myocardial Infarction 54) trial studied 2 doses of ticagrelor, 90 mg twice a day (bid) and 60 mg bid, for long-term prevention of ischemic events in patients with prior myocardial infarction. Both doses similarly reduced the rate of ischemic events versus placebo. The pharmacokinetics and pharmacodynamics of ticagrelor 60 mg bid have not been studied. ObjectivesIn this study, the authors sought to study the pharmacokinetics and pharmacodynamics for ticagrelor 60 mg compared with 90 mg bid. MethodsA total of 180 patients who received >4 weeks of study medication had blood sampling in the morning pre-maintenance dose and again 2 h post-dose. All patients received aspirin. Plasma levels of ticagrelor and its active metabolite AR-C124910XX were determined. P2Y12 inhibition was assessed by the VerifyNow P2Y12 assay (Accumetrics, Inc., San Diego, California) (P2Y12 reaction units [PRU]), light transmittance aggregometry (adenosine diphosphate 5 and 20 μmol/l and arachidonic acid), and vasodilator-stimulated phosphoprotein phosphorylation assays. VerifyNow Aspirin assays and serum thromboxane B2 measurements were performed. ResultsMean pre- and post-dose plasma levels of ticagrelor were 35% and 38% lower, respectively, with 60 mg versus 90 mg. Both doses achieved high levels of platelet inhibition pre- and post-dose, with numerically slightly more variability with 60 mg: mean (SD) pre-dose PRU values were 59 ± 63 and 47 ± 43 for ticagrelor 60 and 90 mg, respectively (p = 0.34). High platelet reactivity, determined as PRU >208, was rare with the 60-mg pre-dose and was absent post-dose. Platelet reactivity pre- and post-dose, as measured by light transmittance aggregometry or vasodilator-stimulated phosphoprotein assays, was numerically but not significantly lower with 90 mg than with 60 mg. Aspirin response was not affected by either dose. ConclusionsTicagrelor 60 mg bid achieved high levels of peak and trough platelet inhibition in nearly all patients, similar to that with 90 mg bid, helping to explain the efficacy of the lower ticagrelor dose in PEGASUS-TIMI 54.

Riociguat (BAY 63-2521) and aspirin: a randomized, pharmacodynamic, and pharmacokinetic interaction study.

In preclinical studies, drugs that increase cyclic guanosine monophosphate levels have been shown to influence platelet function/aggregation; however, the effect of riociguat on human platelets is unclear. Aspirin, a platelet inhibitor, is likely to be given concomitantly in patients receiving riociguat. It is therefore important to establish clinically whether (1) riociguat affects platelet function and (2) aspirin and riociguat interact. This randomized, open-label, crossover study investigated potential pharmacodynamic and pharmacokinetic interactions between these drugs in healthy male volunteers (N = 18). There were 3 treatment regimens: a single morning dose of riociguat 2.5 mg, aspirin 500 mg on 2 consecutive mornings, and both treatments together, with riociguat given on the second morning. Fifteen participants were available for pharmacodynamic/pharmacokinetic analysis. There was no effect of riociguat alone on bleeding time, platelet aggregation, and serum thromboxane B2 levels. The effects of aspirin on these parameters were not influenced by concomitant administration of riociguat. The pharmacokinetic profile of riociguat showed interindividual variability, which was independent of aspirin coadministration. Six of 17 participants available for safety evaluation reported at least 1 treatment-emergent adverse event. All adverse events were of mild severity, apart from 1 report of moderate headache. No serious adverse events occurred. In conclusion, riociguat demonstrated no clinically relevant pharmacodynamic or pharmacokinetic interactions with aspirin at the doses used in this study in healthy men; coadministration of riociguat and aspirin should therefore not require any dose adjustment for either drug.

Relationship between high on aspirin platelet reactivity and oxidative stress in coronary artery by-pass grafted patients.

The aim of the study was to assess the responsiveness of blood platelets to acetylsalicylic acid (ASA) in patients following coronary artery bypass grafting (CABG) surgery with relation to oxidative and antioxidative plasma status. The study included 37 patients treated with the CABG procedure. During the first 24 h after CABG patients were given 300 mg of ASA with the following dose of 150 mg daily. The blood was collected before the procedure and 10 days after. Whole blood platelet aggregation induced with arachidonic acid, collagen and adenosine diphosphate (ADP) was performed together with whole blood generation of thromboxane B2 (TxB2). Oxidative stress was measured before and 10 days after CABG with total oxidative plasma status (TOS) and total antioxidative status of the plasma (TAS). TOS/TAS index was calculated. We observed a significant increase in the TOS and TOS/TAS index and ADP-induced aggregation 10 days after CABG in comparison with its level before operation. There was a significant decrease in the arachidonic acid-induced aggregation and serum TxB2 level. Patients with ADP-induced and collagen-induced aggregation in the upper quartile had significantly higher TOS and TOS/TAS index before (ADP) and after the operation (ADP and collagen). There were 19 patients (51%) with high on aspirin platelet reactivity after CABG who had also higher TOS and TOS/TAS index and lower TAS value in comparison with aspirin responders. Despite ASA use, increased oxidative stress after CABG can overcome its antiplatelet effect and increase platelet activation through other pathways.

Cardiovascular events occur independently of high on-aspirin platelet reactivity and residual COX-1 activity in stable cardiovascular patients.

Several studies have indicated that approximately 25 % of patients treated with aspirin exhibit high on-treatment platelet reactivity (HTPR), which is potentially associated with cardiovascular events (CVEs). However, this association is still controversial, since the mechanisms by which HTPR contributes to CVEs remain unclear and a no standardised definition of HTPR has been established. To determine whether HTPR is associated with CVE recurrence and what type of assay would best predict CVE recurrence, we conducted a multicentre prospective cohort study of 592 stable cardiovascular outpatients treated with aspirin monotherapy for secondary prevention. Their HTPR was determined by arachidonic acid- or collagen-induced aggregation assays using two different agonist concentrations. Residual cyclooxygenase (COX)-1 activity was assessed by measuring serum thromboxane (TX)B2 or urinary 11-dehydro TXB2. Shear-induced platelet thrombus formation was also examined. We followed all patients for two years to evaluate how these seven indexes were related to the recurrence of CVEs (cerebral infarction, transient ischaemic attack, myocardial infarction, unstable angina, revascularisation, other arterial thrombosis, or cardiovascular death). Of 583 patients eligible for the analysis, CVEs occurred in 69 (11.8 %). A Cox regression model identified several classical risk factors associated with CVEs. However, neither HTPR nor high residual COX-1 activity was significantly associated with CVEs, even by applying cut-off values suggested in previous reports or a receiver-operating characteristic analysis. In conclusion, recurrence of CVEs occurred independently of HTPR and residual COX-1 activity. Thus, our findings do not support the use of platelet or COX-1 functional testing for predicting clinical outcomes in stable cardiovascular patients.

Population Trends in Aspirin Use for Cardiovascular Disease Prevention 1980-2009: The Minnesota Heart Survey.

BackgroundDaily low‐dose aspirin is recommended for primary prevention of myocardial infarction and stroke in higher‐risk patients. Population trends in aspirin use for cardiovascular disease (CVD) prevention in an urban population (Minneapolis/St. Paul, 2010 population 2.85 million) from 1980 to 2009 were evaluated.Methods and ResultsSurveys of randomly selected adults aged 25 to 74 years were collected at 5‐year intervals. Self‐reports of regular aspirin use for CVD prevention and history of CVD were obtained. Six cross‐sectional surveys included 12 281 men and 14 258 women. Age‐adjusted aspirin use for primary prevention increased during this period from 1% to 21% among men and 1% to 12% among women. Aspirin use was highest in those aged 65 to 74 years. For secondary prevention, age‐adjusted aspirin use increased from 19% to 74% among men and 11% to 64% among women. While data are based on self‐report, a substudy using a biochemical indicator of aspirin use (serum thromboxane B2) supports the validity of self‐report.ConclusionsAspirin for CVD prevention is commonly used by a large and growing portion of the general population. It is not known if this is based on professional advice or self‐prescribed use. It is also likely that many who would benefit do not use aspirin and others use aspirin inappropriately.