Patients with essential thrombocythemia (ET) are treated with once-daily low-dose aspirin to prevent thrombosis, but their accelerated platelet turnover shortens the antiplatelet effect. The short-term Aspirin Regimens in EsSential Thrombocythemia trial showed that twice-daily aspirin dosing restores persistent platelet thromboxane (TX) inhibition. However, the long-term pharmacodynamic efficacy, safety and tolerability of twice-daily aspirin remain untested. We performed a multicenter, randomized, open-label, blinded-endpoint, phase-2 trial in which 242 patients with ET were randomized to 100 mg aspirin twice- or once-daily and followed for 20 months. The primary endpoint was the persistence of low serum TXB2, a surrogate biomarker of antithrombotic efficacy. Secondary endpoints were major and clinically relevant non-major bleedings, serious vascular events, symptom burden assessed by validated questionnaires, and in vivo platelet activation. Serum TXB2 was consistently lower in the twice-daily versus once-daily regimen on 10 study visits over 20 months: median 3.9 ng/mL versus 19.2 ng/mL, respectively; p < .001; 80% median reduction; 95% CI, 74%-85%. No major bleeding occurred. Clinically relevant non-major bleedings were non-significantly higher (6.6% vs. 1.7%), and major thromboses lower (0.8% vs. 2.5%) in the twice-daily versus once-daily group. Patients on the twice-daily regimen had significantly lower frequencies of disease-specific symptoms and severe hand and foot microvascular pain. Upper gastrointestinal pain was comparable in the two arms. In vivo platelet activation was significantly reduced by the twice-daily regimen. In patients with ET, twice-daily was persistently superior to once-daily low-dose aspirin in suppressing thromboxane biosynthesis and reducing symptom burden, with no detectable excess of bleeding and gastrointestinal discomfort.

BACKGROUND: Thromboxane metabolites could indirectly reflect platelet activation, among which 11-dehydro-thromboxane B2 (11dhTxB2) and 11-dehydro-2, 3-dinor thromboxane B2 (11dh23dinorTxB2) are two stable metabolites that are abundant in urine, and both are closely related to disease progression and drug use. However, most clinical application studies have focused on the single indicator of 11dhTxB2. We propose an LC-MS/MS method suitable for routine clinical screening with simultaneous determination of both metabolites and conduct preliminary studies in different populations.
RESULTS: The thromboxane metabolites were extracted by liquid-liquid extraction and determined by LC-MS/MS. Reference intervals (RI) were established in 333 healthy adults and validated in 25 patients with coronary atherosclerosis (CA). This LC-MS/MS method was over a wide quantitative range (0.1-10 μmol/L), the imprecision and accuracy were 5.2 %-11 % and 89.3 %-106.5 %, and was suitable for clinical routine quantitative screening. The 95th percentile RI of unire 11dhTxB2 was 1220 (95 % CI: 1048, 1376) pg mg Cr -1, for 11dh23dinorTxB2, RI was 908 (95 % CI: 821, 1102) pg mg Cr -1. For the first time, we found a significant correlation between 11dhTxB2 and 11dh23dinorTxB2 in both healthy adults (r = 0.67, P < 0.001) and CA patients (r = 0.77, P < 0.001).
CONCLUSIONS: The establishment of RI provides a reference for diseases related to platelet activation and the use of drugs, and the first discovery of the correlation between 11dhTxB2 and 11dh23dinorTxB2 in urine provides a new possibilitie for the diagnostic and prognostic of cardiovascular diseases.

Metabolomics is an emerging and powerful bioanalytical method supporting clinical investigations. Serum and plasma are commonly used without rational prioritization. Serum is collected after blood coagulation, a complex biochemical process involving active platelet metabolism. This may affect the metabolome and increase the variance, as platelet counts and function may vary substantially in individuals. A multiomics approach systematically investigating the suitability of serum and plasma for clinical studies demonstrated that metabolites correlated well (n = 461, R2 = 0.991), whereas lipid mediators (n = 83, R2 = 0.906) and proteins (n = 322, R2 = 0.860) differed substantially between specimen. Independently, analysis of platelet releasates identified most biomolecules significantly enriched in serum compared to plasma. A prospective, randomized, controlled parallel group metabolomics trial with acetylsalicylic acid administered for 7 days demonstrated that the apparent drug effects significantly differ depending on the analyzed specimen. Only serum analyses of healthy individuals suggested a significant downregulation of TXB2 and 12-HETE, which were specifically formed during coagulation in vitro. Plasma analyses reliably identified acetylsalicylic acid effects on metabolites and lipids occurring in vivo such as an increase in serotonin, 15-deoxy-PGJ2 and sphingosine-1-phosphate and a decrease in polyunsaturated fatty acids. The present data suggest that plasma should be preferred above serum for clinical metabolomics studies as the serum metabolome may be substantially confounded by platelets.

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Systemic thromboxane A2 generation, assessed by quantifying the concentration of stable thromboxane B2 metabolites (TXB2-M) in the urine adjusted for urinary creatinine, is strongly associated with mortality risk. We sought to define optimal TXB2-M cutpoints for aspirin users and nonusers and determine if adjusting TXB2-M for estimated glomerular filtration rate (eGFR) in addition to urinary creatinine improved mortality risk assessment.
Urinary TXB2-M were measured by competitive ELISA in 1363 aspirin users and 1681 nonusers participating in the Framingham Heart Study. Cutpoints were determined for TXB2-M and TXB2-M/eGFR using log-rank statistics and used to assess mortality risk by Cox proportional hazard modeling and restricted mean survival time. Multivariable models were compared using the Akaike Information Criterion (AIC). A cohort of 105 aspirin users with heart failure was used for external validation.
Optimized cutpoints of TXB2-M were 1291 and 5609 pg/mg creatinine and of TXB2-M/eGFR were 16.6 and 62.1 filtered prostanoid units (defined as pg·min/creatinine·mL·1.73 m2), for aspirin users and nonusers, respectively. TXB2-M/eGFR cutpoints provided more robust all-cause mortality risk discrimination than TXB2-M cutpoints, with a larger unadjusted hazard ratio (2.88 vs 2.16, AIC P < 0.0001) and greater differences in restricted mean survival time between exposure groups (1.46 vs 1.10 years), findings that were confirmed in the external validation cohort of aspirin users. TXB2-M/eGFR cutpoints also provided better cardiovascular/stroke mortality risk discrimination than TXB2-M cutpoints (unadjusted hazard ratio 3.31 vs 2.13, AIC P < 0.0001).
Adjustment for eGFR strengthens the association of urinary TXB2-M with long-term mortality risk irrespective of aspirin use.

OBJECTIVE: Thromboxane (TX) A2, released by activated platelets, plays an important role in atherothrombosis. Urinary 11-dehydro-TXB2 (U-TXM), a stable metabolite reflecting the whole-body TXA2 biosynthesis, is reduced by ∼70% by daily low-dose aspirin. The U-TXM represents a non-invasive biomarker of in vivo platelet activation and is enhanced in patients with diabetes. This study assessed whether U-TXM is associated with the risk of future serious vascular events or revascularizations (SVE-R), major bleeding, or cancer in patients with diabetes.
METHODS: The U-TXM was measured pre-randomization to aspirin or placebo in 5948 people with type 1 or 2 diabetes and no cardiovascular disease, in the ASCEND trial. Associations between log U-TXM and SVE-R (n = 618), major bleed (n = 206), and cancer (n = 700) during 6.6 years of follow-up were investigated by Cox regression; comparisons of these associations with the effects of randomization to aspirin were made.
RESULTS: Higher U-TXM was associated with older age, female sex, current smoking, type 2 diabetes, higher body size, urinary albumin/creatinine ratio of ≥3 mg/mmol, and higher estimated glomerular filtration rate. After adjustment for these, U-TXM was marginally statistically significantly associated with SVE-R and major bleed but not cancer [hazard ratios per 1 SD higher log U-TXM (95% confidence interval): 1.09 (1.00-1.18), 1.16 (1.01-1.34), and 1.06 (0.98-1.14)]. The hazard ratio was similar to that implied by the clinical effects of randomization to aspirin for SVE-R but not for major bleed.
CONCLUSIONS: The U-TXM was log-linearly independently associated with SVE-R in diabetes. This is consistent with the involvement of platelet TXA2 in diabetic atherothrombosis.

OBJECTIVE: This study aimed to assess the association between dietary inflammation index with serum Nitric oxide, Prostacyclin, and Thromboxane B2 among Prinzmetal angina patients and healthy persons.
RESULTS: This case-control study was conducted among 120 Prinzmetal angina patients and 120 healthy persons referred to the Ardabil Imam Khomeini Hospital between 2021 and 2022. Blood samples were gained from all study participants for measurement of serum Nitric oxide, Prostacyclin, and Thromboxane B2. The serum Nitric oxide in patients who had higher DII was less than in patients with less dietary inflammation index (β = -0.75 p = 0.02). The serum Prostacyclin level in patients with greater dietary inflammation index was 0.68 ng/ml less than in patients with less dietary inflammation index (β = -0.68 p = 0.04). The level of serum Thromboxane B2 had a positive association with dietary inflammation index (β = 0.81 p = 0.04).
CONCLUSIONS: In Prinzmetal angina patients, more dietary inflammation index can increase the serum Thromboxane B2 and decrease the serum Nitric oxide and Prostacyclin. More clinical trial study is needed to confirm these results.

VerifyNow (VN) test is a less laborious method to assess pharmacodynamics (PD) compared to light transmittance aggregometry (LTA). VN assay has not been used to study the immediate PD effects of acetylsalicylic acid (ASA). Ten healthy volunteers were randomly assigned to a single 162 or 650 mg dose of chewed and swallowed ASA. Pharmacodynamic and pharmacokinetic measurements were performed at baseline and serially up to 60 min after ASA administration. Onset by VN was 20 ± 7 min with 162 mg and 13 ± 7 min with 650 mg ASA (p = .07). Onset by 1 mM AA-induced PA was 13 ± 12 min with 162 mg and 7 ± 3 min with 650 mg ASA (p=NS). VN correlated with AA-induced PA (r = 0.80, p < .001) and serum TxB2 levels (r = 0.76, p < .001). 95% inhibition of serum TxB2 was achieved at 38 ± 22 min and 22 ± 8 min with the 162 and 650 mg ASA, respectively (p = .08). The onset and extent of the antiplatelet effect of 650 mg ASA is numerically faster and greater than the 162 mg dose. VN identifies the onset, extent, and dose response to ASA therapy. The ease of using VN should facilitate multicenter PD investigations of ASA.
Aspirin (acetylsalicylic acid) is an important drug widely used to prevent adverse ischemic events in patients with cardiovascular disease. Platelet aggregation and thromboxane B2 levels in blood samples by complex laboratory methods are used to assess platelet response to aspirin. VerifyNow assay is a simple laboratory test that has not been used to assess the immediate effect of aspirin. In this study, conducted in 10 healthy volunteers, we compared the immediate platelet response to aspirin by serially assessing platelet aggregation by aggregometry and VerifyNow assay, and thromboxane B2 levels. We also measured plasma levels of acetylsalicylic acid and salicylic acid. Our study demonstrated that the VerifyNow Aspirin test identifies the onset, extent, and dose-response to aspirin therapy. The ease of using the VerifyNow test should facilitate multicenter pharmacodynamic investigations of aspirin.

BACKGROUND: Low dose aspirin is recommended for prevention of preeclampsia, however there is not consensus on the appropriate dose. Pregnancy specific changes have the potential to impact the pharmacology of aspirin in pregnancy, however there are very limited studies on aspirin pharmacokinetics in pregnancy and none linking pharmacokinetics (PK, drug dose and drug level) to pharmacodynamics (PD, drug dose and physiologic response) in pregnancy. As a result, we do not have a good understanding of the pharmacologic response to aspirin in pregnancy, which has important implications for clinical efficacy. We sought to describe the PK and PD of aspirin through pregnancy and to identify individual covariates that impacted aspirin PK/PD.
OBJECTIVE: We sought to describe the PK and PD of aspirin through pregnancy (first and third trimester), to identify covariates that significantly impact aspirin PK and to identify the relationship between aspirin PK and PD.
METHODS: This is a prospective study of patients at high risk for preeclampsia recommended to take 81 mg aspirin daily. This study involved 3 visits as follows: (1) baseline, first trimester (10-16 weeks of gestation) 6-hour PK visit, done before initiation of aspirin; (2) follow-up 1: 2 to 4 weeks after aspirin initiation; and (3) follow-up 2: third trimester 6-hour PK visit (28-32 weeks of gestation). The following were assessed at each visit: weight or body mass index, platelet function analysis-100 (Siemens), urinary thromboxane B2, serum thromboxane B2, and plasma salicylic acid. The PK visits consisted of blood work done at baseline (predose), administration of 81 mg nonenteric coated aspirin, and then plasma blood level of salicylic acid assessed at 30 minutes and then hourly 1 to 6 hours after dose. Pearson correlation and multivariable regression were used to identify associations between parameters and identify relevant covariates. Log-adjusted values were used for regression analysis. P<.05 was considered statistically significant.
RESULTS: Nineteen participants were included with first trimester data, and 16 with third trimester data. There was no statistically significant change in mean PK parameters between the first and third trimester, although there was a trend to lower peak concentration in the third than in the first trimester (P=.08). In multivariable regression, baseline obesity and current body mass index as a continuous measures were negatively associated with log-adjusted peak salicylic acid concentration (-0.28 [-0.46 to -0.11], P=.003 and -0.02 [-0.03 to -0.009], P=.001, respectively) and log-adjusted plasma salicylic acid area under the curve 0 to 6 hours postdose (-0.25 [-0.45 to 0.05], P=.02, -0.04 [-0.07 to -0.01], P=.008 respectively). There was a significant decrease in urinary thromboxane 2 to 4 weeks after aspirin initiation compared with baseline, which correlated with a concomitant increase in platelet function analysis-100 closure time. In multivariable regression model, there was a strong association between plasma salicylic acid concentration (area under the curve 0-6 hours postdose) and urinary thromboxane (B=-3.12 [-5.38 to -1.04], P=.006), and with urinary thromboxane suppression and platelet inhibition, platelet function analysis-100 (-0.23 [-0.31 to -0.14], P<.001). With progressive thromboxane suppression, platelet inhibition (platelet function analysis-100 closure time) increased. Individual comorbidities, including weight, hypertension, and pregestational diabetes (Type I or II), also impacted aspirin response.
CONCLUSIONS: We have demonstrated the relationship between individual factors, plasma concentrations of salicylic acid, thromboxane suppression, and platelet inhibition at a single dose (81 mg) of aspirin taken through pregnancy. Our findings suggest that dose modification of aspirin in pregnancy may help to achieve the optimal response. Our results may be used to facilitate computational modeling to identify optimal dosing, taking into consideration individual factors.

Despite decades of investigations, the optimal assessment of the \"therapeutic response\" to early after loading dose of acetylsalicylic acid (ASA) remains unclear. Limited information is available on the relation between pharmacodynamic (PD) and pharmacokinetic (PK) measurements assessed immediately after ASA administration. Serial PD and PK analyses were performed immediately after a single 162 or 650 mg dose of chewed and swallowed ASA in ten healthy adults. ASA response was defined as > 95% inhibition of serum thromboxane (Tx)B2, < 550 aspirin reaction units (ARU) by VerifyNow Aspirin (VN) test, and ≤ 20% arachidonic acid (AA)-induced platelet aggregation (PA). Correlation analyses between PK and PD measurements and receiver operating characteristic (ROC) curve analyses were performed. ASA response measured by VN test and AA-induced PA was achieved within 30 min of ASA administration. A correlation was observed between ARU and AA-induced maximum PA (r = 0.69, p < 0.001), serum TxB2 (r = 0.74 and p < 0.001), and serum TxB2 inhibition (r = 0.79, p < 0.001). In ROC curve analyses, ≤ 558 ARU and ≤ 7% AA-induced PA were associated with > 95% inhibition of TxB2. 686 ng/ml plasma ASA cut-off point was associated with > 95% inhibition of serum TxB2, ≤ 7% 1 mM AA-induced PA, and ≤ 585 ARU. A modest ~ 50% inhibition of TxB2 inhibition was associated with marked inhibition of 1 mM AA-induced platelet aggregation by LTA. Our analyses demonstrated important relationships between pharmacodynamic, and pharmacokinetic parameters measured immediately following oral ASA and cutoff values for ARU and AA-induced PA that is associated with > 95% inhibition of serum TxB2.