Clopidogrel

Effects of the Thiol Methyltransferase Inhibitor (±)-2,3-Dichloro-α-Methylbenzylamine (DCMB) on the Pharmacokinetics and Metabolism of Vicagrel in Rats

P2Y12 receptor inhibitors are commonly used in clinical antiplatelet therapy, typically alongside other medications. Vicagrel, a promising P2Y12 receptor inhibitor, has submitted a new drug marketing application to the United States Food and Drug Administration. Its primary metabolites and some metabolic pathways are identical to those of clopidogrel. The aim of this study was to investigate the effects of the thiol methyltransferase inhibitor (±)-2,3-dichloro-α-methylbenzylamine (DCMB) on the metabolism and pharmacokinetics of vicagrel. In vitro incubation with human and rat liver microsomes revealed that DCMB significantly inhibited the methylation of vicagrel's thiol metabolite M15-1. Rats were orally administered 6 mg/kg [14C]vicagrel (100 μCi/kg) 1 hour after peritoneal injection with or without DCMB (80 mg/kg). Compared with the control group, the plasma of DCMB-pretreated rats exhibited maximum plasma concentration (C max) decrease and time to reach C max (T max) delay for all vicagrel-related substances, the methylation product of the thiol metabolite (M9-2), and the derivatization product of the active thiol metabolite (MP-M15-2). However, no significant changes in area under the curve (AUC) or half-life (t 1/2) were observed. DCMB had negligible effect on the total radiological recovery of vicagrel within 72 hours, although the rate of vicagrel excretion slowed down within 48 hours. DCMB had a negligible impact on the metabolic pathway of vicagrel. Overall, the present study found that DCMB did not significantly affect the total exposure, metabolic pathways, metabolite profiles, or total excretion rates of vicagrel-related metabolites in rats, but led to C max decrease, T max delay, and slower excretion rate within 48 hours. SIGNIFICANCE STATEMENT: This study used liquid chromatography-tandem mass spectrometry combined with radiolabeling technology to investigate the effects of the thiol methyltransferase inhibitor (±)-2,3-dichloro-α-methylbenzylamine on the absorption, metabolism, and excretion of vicagrel in rats. This work helps to better understand the in vivo metabolism of active thiol metabolites of P2Y12 inhibitors such as clopidogrel, vicagrel, etc.

Trialkoxysilane-Induced Iridium-Catalyzed para-Selective C-H Bond Borylation of Arenes

An ideal approach for the construction of aryl boron compounds is to selectively replace a C-H bond in arenes with a C-B bond, and controlling regioselectivity is one of the most challenging aspects of these transformations. Herein, we report an iridium-catalyzed trialkoxysilane protecting group-assisted regioselective C-H borylation of arenes, including derivatives of benzaldehydes, acetophenones, benzoic acids, benzyl alcohols, phenols, aryl silanes, benzyl silanes, and multi-functionalized aromatic rings are all well tolerated and gave the para -selective C-H borylation products in a short time without the requirement of inert gases atmosphere. The site-selective C-H borylation can be adjustable by installing the developed trialkoxysilane protecting group on different functional groups on one aromatic ring. Importantly, the preparation process of the trialkoxychlorosilane is efficient and scalable. Mechanistic and computational studies reveal that the steric hindrance of the trialkoxysilane protecting group plays a key role in dictating the para-selectivity.

Discovery and Mechanism Study of SARS-CoV-2 3C-like Protease Inhibitors with a New Reactive Group

3CLpro is an attractive target for the treatment of COVID-19. Using the scaffold hopping strategy, we identified a potent inhibitor of 3CLpro (3a) that contains a thiocyanate moiety as a novel warhead that can form a covalent bond with Cys145 of the protein. Tandem mass spectrometry (MS/MS) and X-ray crystallography confirmed the mechanism of covalent formation between 3a and the protein in its catalytic pocket. Moreover, several analogues of compound 3a were designed and synthesized. Among them, compound 3h shows the best inhibition of 3CLpro with an IC50 of 0.322 μM and a kinact/Ki value of 1669.34 M-1 s-1, and it exhibits good target selectivity for 3CLpro against host proteases. Compound 3c inhibits SARS-CoV-2 in Vero E6 cells (EC50 = 2.499 μM) with low cytotoxicity (CC50 > 200 μM). These studies provide ideas and insights to explore and develop new 3CLpro inhibitors in the future.

The effects of P2Y12 adenosine receptors' inhibitors on central and peripheral chemoreflexes

Introduction: The most common side effect of ticagrelor is dyspnea, which leads to premature withdrawal of this life-saving medication in 6.5% of patients. Increased chemoreceptors' sensitivity was suggested as a possible pathophysiological explanation of this phenomenon; however, the link between oversensitization of peripheral and/or central chemosensory areas and ticagrelor intake has not been conclusively proved. Methods: We measured peripheral chemoreceptors' sensitivity using hypoxic ventilatory response (HVR), central chemoreceptors' sensitivity using hypercapnic hyperoxic ventilatory response (HCVR), and dyspnea severity before and 4 ± 1 weeks following ticagrelor initiation in 11 subjects with chronic coronary syndrome undergoing percutaneous coronary intervention (PCI). The same tests were performed in 11 age-, sex-, and BMI-matched patients treated with clopidogrel. The study is registered at ClinicalTrials.com at NCT05080478. Results: Ticagrelor significantly increased both HVR (0.52 ± 0.46 vs. 0.84 ± 0.69 L min-1 %-1; p < 0.01) and HCVR (1.05 ± 0.64 vs. 1.75 ± 1.04 L min-1 mmHg-1; p < 0.01). The absolute change in HVR correlated with the change in HCVR. Clopidogrel administration did not significantly influence HVR (0.63 ± 0.32 vs. 0.58 ± 0.33 L min-1%-1; p = 0.53) and HCVR (1.22 ± 0.67 vs. 1.2 ± 0.64 L min-1 mmHg-1; p = 0.79). Drug-related dyspnea was reported by three subjects in the ticagrelor group and by none in the clopidogrel group. These patients were characterized by either high baseline HVR and HCVR or excessive increase in HVR following ticagrelor initiation. Discussion: Ticagrelor, contrary to clopidogrel, sensitizes both peripheral and central facets of chemodetection. Two potential mechanisms of ticagrelor-induced dyspnea have been identified: 1) high baseline HVR and HCVR or 2) excessive increase in HVR or HVR and HCVR. Whether other patterns of changes in chemosensitivities play a role in the pathogenesis of this phenomenon needs to be further investigated.

Palladium-catalyzed enantioselective three-component synthesis of α-arylglycine derivatives from glyoxylic acid, sulfonamides and aryltrifluoroborates

A palladium-catalyzed enantioselective three-component reaction of glyoxylic acid, sulfonamides and aryltrifluoroborates is described. This process provides modular access to the important α-arylglycine motif in moderate to good yields and enantioselectivies. The formed α-arylglycine products constitute useful building blocks for the synthesis of peptides or arylglycine-containing natural products.

Palladium-catalyzed asymmetric three-component reaction between glyoxylic acid, sulfonamides and arylboronic acids for the synthesis of α-arylglycine derivatives

A palladium-catalyzed asymmetric three-component synthesis of α-arylglycine derivatives starting from glyoxylic acid, sulfonamides and arylboronic acids is reported. This novel, operationally simple method offers access to the α-arylglycine scaffold in good yields and enantioselectivities. The utilization of α tailored catalyst system enables the enantioselective synthesis of the desired α-arylglycines despite a fast racemic background reaction. The obtained products can be directly employed as building blocks in peptide synthesis.

Is it Safe to Continue Clopidogrel in Elective Hip and Knee Arthroplasty?

BACKGROUND

No evidence-based guidelines exist for the perioperative use of clopidogrel in elective hip and knee arthroplasty patients. This study compares the preoperative, intraoperative, and postoperative outcomes of total hip and knee arthroplasty in patients maintained on clopidogrel and with patients whose clopidogrel was held before surgery.

METHODS

We retrospectively identified 158 patients taking clopidogrel before undergoing elective total hip or knee arthroplasty. Patients were stratified for having clopidogrel held or continued, based on the interval between latest dose and date of surgery. The primary end points were receipt of transfusion and readmission within 90 days of surgery. Secondary end points were the incidence of complications such as bleeding, infection, re-operation, and major cardiac or neurologic events such as myocardial infarction or stroke during the 90-day postoperative period.

RESULTS

The two cohorts had similar demographics. Patients who continued clopidogrel were more likely to receive a blood transfusion postoperatively (9.1% vs 0%, P = .005), but there was no difference in wound drainage (P = .65), wound infection (P = .24), readmission (P = .74), major complications (P = .64), length of stay (P = .70), or mortality (P = .42). Patients who continued clopidogrel before surgery were more likely to have received general anesthesia (P < .001) per anesthesia protocol, however, three such patients did receive spinal anesthesia without any complications. With cementless implants, blood loss was not different between clopidogrel groups.

CONCLUSION

Patients undergoing elective total hip and knee arthroplasty may be safely maintained on clopidogrel without an increased risk of wound complications, infections, length of stay, readmission, reoperation, major medical complications, or mortality. Further prospective research is warranted to confirm the effects of continuing clopidogrel in patients undergoing elective hip and knee arthroplasty.

Effect of CYP2C19 genetic variants on bleeding and major adverse cardiovascular events in a cohort of Arab patients undergoing percutaneous coronary intervention and stent implantation

INTRODUCTION

One-third of patients have clopidogrel resistance that may lead to major adverse cardiac events (MACEs). By contrast, it was found that some clopidogrel-treated patients have hyperresponsive platelets that are associated with higher bleeding risk. Several studies have shown that polymorphisms in the gene encoding the CYP2C19 contribute to the variability in response to clopidogrel. Data on genetic and nongenetic factors affecting clopidogrel response in the Arab population are scarce. In this prospective cohort study, we sought to assess the association between the increased function allele (CYP2C19*17) and bleeding events, and validate the effect of the CYP2C19 genetic variants and nongenetic factors on the incidence of MACEs.

METHODS

Blood samples were collected from patients that were undergoing percutaneous coronary intervention and receiving clopidogrel at the Heart Hospital, a specialist tertiary hospital in Doha, Qatar. Patients were followed for 12 months. Genotyping was performed for CYP2C19*2, *3, and *17 using TaqMan assays.

RESULTS

In 254 patients, the minor allele frequencies were 0.13, 0.004, and 0.21 for *2, *3, and *17, respectively. Over a 12-month follow-up period, there were 21 bleeding events (8.5 events/100 patient-year). CYP2C19*17 carriers were found to be associated with increased risk of bleeding (OR, 21.6; 95% CI, 4.8-96.8; P < 0.0001). CYP2C19*2 or *3 carriers were found to be associated with increased risk of baseline and incident MACE combined (OR, 8.4; 95% CI, 3.2-23.9; P < 0.0001).

CONCLUSION

This study showed a significant association between CYP2C19*17 allele and the increased risk of bleeding, and CYP2C19*2 or *3 with MACE outcomes.

P2Y12 antagonists: Approved drugs, potential naturally isolated and synthesised compounds, and related in-silico studies

P2Y₁₂ is a platelet surface protein which is responsible for the amplification of P2Y₁ response. It plays a crucial role in platelet aggregation and thrombus formation through an ADP-induced platelet activation mechanism. Despite that P2Y₁₂ platelets' receptor is an excellent target for developing antiplatelet agents, only five approved medications are currently in clinical use which are classified into thienopyridines and nucleoside-nucleotide derivatives. In the past years, many attempts for developing new candidates as P2Y₁₂ inhibitors have been made. This review highlights the importance and the role of P2Y₁₂ receptor as part of the coagulation cascade, its reported congenital defects, and the type of assays which are used to verify and measure its activity. Furthermore, an overview is given of the clinically approved medications, the potential naturally isolated inhibitors, and the synthesised candidates which were tested either in-vitro, in-vivo and/or clinically. Finally, we outline the in-silico attempts which were carried out using virtual screening, molecular docking and dynamics simulations in efforts of designing novel P2Y₁₂ antagonists. Various phytochemical classes might be considered as a corner stone for the discovery of novel P2Y₁₂ inhibitors, whereas a wide range of ring systems can be deliberated as leading scaffolds in that area synthetically and theoretically.

Drug-based therapeutic strategies for COVID-19-infected patients and their challenges

Emerging epidemic-prone diseases have introduced numerous health and economic challenges in recent years. Given current knowledge of COVID-19, herd immunity through vaccines alone is unlikely. In addition, vaccination of the global population is an ongoing challenge. Besides, the questions regarding the prevalence and the timing of immunization are still under investigation. Therefore, medical treatment remains essential in the management of COVID-19. Herein, recent advances from beginning observations of COVID-19 outbreak to an understanding of the essential factors contributing to the spread and transmission of COVID-19 and its treatment are reviewed. Furthermore, an in-depth discussion on the epidemiological aspects, clinical symptoms and most efficient medical treatment strategies to mitigate the mortality and spread rates of COVID-19 is presented.

Edaravone Combined with Clopidogrel Is Beneficial to Improve Efficacy, Neurological Impairment, and Life Function in Acute Cerebral Infarction Patients

Objective

This research aimed at investigating the efficacy of edaravone combined with clopidogrel on acute cerebral infarction (ACI) and its influence on the neurological deficit and life function.

Methods

Totally, 154 ACI cases were included and then divided into the control group (CG) (n = 71) and research group (RG) (n = 83) according to the treatment methods. Patients in the CG were treated with clopidogrel alone, and those in the RG were under edaravone-clopidogrel combination therapy. The efficacy, adverse reactions, NIHSS score, cerebral hemodynamic indexes, and Fugl-Meyer scale (FMA) and Barthel index (BI) of activities of daily living (ADL) scores were observed.

Results

Compared with before treatment, the symptoms of both groups were improved after treatment: the NIHSS scores decreased, FMA and ADL scores increased, and cerebral hemodynamic indexes were improved. Compared with the CG, the efficacy and cerebral hemodynamic indexes of the RG were better, the adverse reactions were equivalent, the NIHSS score was lower, and the ADL and FMA scores were higher.

Conclusion

Edaravone combined with clopidogrel can effectively treat ACI and improve the neurological deficit and life function of patients.

Development and validation of a LC-MS/MS method for the enantioseparation and determination of clopidogrel bisulfate in beagle plasma and its application to a stereoselective pharmacokinetic study

A rapid and sensitive chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the enantioseparation and determination of clopidogrel bisulfate enantiomers in beagle plasma was established and successfully applied to a stereoselective pharmacokinetic study. The chromatographic separation was achieved on an Ultron ES-OVM column (150 × 2.0 mm, 5 μm) with acetonitrile-ammonium acetate (10 mM, pH 4.5) (22:78, v/v) at a flow rate of 0.3 mL/min. The mass detection was conducted using multiple reaction monitoring mode with the transition of the m/z 322.00→212.00 for clopidogrel and m/z 285.00→193.00 for diazepam (IS), respectively. The calibration curve was linear at the range of 1-800 ng/mL (r²>0.997) for each enantiomer. The intra- and inter-day precision (CV%) was within 10.9 % and the accuracy was at the range of 88.5 %-101.3 % for both enantiomers. The extraction recovery was >90.2 % and no obvious matrix effect was observed. The pharmacokinetic results showed that the R-CB have higher Cmax and AUC than that of S-CB. It is first time to find the chiral inversion between S-CB and R-CB in beagle.

Clopidogrel preventive effect based on cytochrome P450 2C19 genotype in ischaemic stroke: protocol for multicentre observational study

INTRODUCTION

Clopidogrel is an antiplatelet agent that is widely used for the secondary prevention of cardiovascular and cerebrovascular events. The genotype of cytochrome P450 2C19 (CYP2C19) differentially affects the liver's metabolism of clopidogrel, which may influence the drug's response and efficacy for cardiovascular event prevention. In contrast to prior studies of patients with coronary artery diseases, little is known about whether the CYP2C19 genotype influences the preventive efficacy of clopidogrel in patients who had a stroke. We hypothesise that, among patients who had an acute ischaemic stroke who are prescribed clopidogrel, the patients with a loss-of-function CYP2C19 genotype (poor and intermediate metabolisers) may be at a higher risk of composite cardiovascular events than those who are non-carriers (extensive metabolisers).

METHODS AND ANALYSIS

This prospective observational multicentre study was designed to determine whether composite cardiovascular events would differ among patients who had an ischaemic stroke prescribed clopidogrel according to CYP2C19 genotype (poor or intermediate vs extensive metabolisers). Inclusion criteria were patients who had an acute ischaemic stroke who underwent CYP2C19 genotype evaluation and received clopidogrel within 72 hours of stroke onset. The primary outcome is composite cardiovascular events (stroke, myocardial infarction, or cardiovascular death) within 6 months after acute ischaemic stroke between patients categorised as poor or intermediate metabolisers and those categorised as extensive metabolisers according to their CYP2C19 genotype.

ETHICS AND DISSEMINATION

The Institutional Review Board of Severance Hospital, Yonsei University College of Medicine approved this study (3-2019-0195). We received study approval from the institutional review board of each participating hospital. We plan to disseminate our findings at relevant conferences and meetings and through peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04072705.

Ponatinib-induced ischemic stroke in larval zebrafish for drug screening

Conventional mammalian ischemic stroke models for drug screening are technically challenging, laborious and time-consuming. In this study, using Ponatinib as an inducer, we developed and characterized a zebrafish ischemic stroke model. This zebrafish ischemic stroke had the cerebral vascular endothelial injury, thrombosis, reduced blood flow, inflammation and apoptosis as well as the reduced motility. The zebrafish ischemic stroke model was validated with 6 known human therapeutic drugs of ischemic stroke (Aspirin, Clopidogrel, Naoxintong capsules, Edaravone, Xingnaojing injection, Shuxuening injection). The mRNA levels of the neovascularization-related gene (vegfaa) and vascular endothelial growth factor receptor gene (VEGFR), neurodevelopment related genes (mbp and α1-tubulin), brain-derived neurotrophic factor (BDNF) and glial cell derived neurotrophic factor (GDNF) were significantly downregulated; whereas apoptosis-related genes (caspase-3, caspase-7, caspase-9 and bax/bcl-2), and inflammatory factor genes (IL-1β, IL-6, IL-10, TNF-α and NF-κB) were remarkably upregulated in the model. These results suggest that the pathophysiology of Ponatinib-induced zebrafish ischemic stroke is similar to that of human ischemic stroke patients and this whole animal model could be used to study the complex cellular and molecular pathogenesis of ischemic stroke and to rapidly identify therapeutic agents.

Combination Therapy Targeting Platelet Activation and Virus Replication Protects Mice against Lethal Influenza Pneumonia

Excessive neutrophils recruited during influenza pneumonia contribute to severe lung pathology through induction of neutrophil extracellular traps (NETs) and release of extracellular histones. We have recently shown that activation of platelets during influenza enhances pulmonary microvascular thrombosis, leading to vascular injury and hemorrhage. Emerging evidence indicates that activated platelets also interact with neutrophils, forming neutrophil-platelet aggregates (NPAs) that contribute to tissue injury. Here, we examined neutrophil-platelet interactions and evaluated the formation of NPAs during influenza pneumonia. We also evaluated the efficacy of clopidogrel (CLP), an antagonist of the ADP-P₂Y₁₂ platelet receptor, alone or in combination with an antiviral agent (oseltamivir) against influenza infection in mice. Our studies demonstrated increased platelet activation and induction of NPAs in influenza-infected lungs, and that these NPAs led to NET release both in vitro and in vivo. Furthermore, neutrophil integrin Mac-1 (macrophage-1 antigen)-mediated platelet binding was critical for NPA formation and NET release. Administration of CLP reduced platelet activation and NPA formation but did not protect the mice against lethal influenza challenge. However, administration of CLP together with oseltamivir improved survival rates in mice compared with oseltamivir alone. The combination treatment reduced lung pathology, neutrophil influx, NPAs, NET release, and inflammatory cytokine release in infected lungs. Taken together, these results provide the first evidence that NPAs formed during influenza contribute to acute lung injury. Targeting both platelet activation and virus replication could represent an effective therapeutic option for severe influenza pneumonia.

MGB Block ARMS Real-Time PCR for Diagnosis of CYP2C19 Mutation in a Chinese Population

Background:

CYP2C19 is an important genetic factor modulating clopidogrel dose requirement.

Objective:

Therefore, a simple and economic genotyping method for predicting the clopidogrel dose of patients would be useful in clinical applications.

Methods:

In this study, the MGB blocker ARMS real-time PCR contained two forward primers, two MGB blockers and a common reverse primer have been used for CYP2C19*2, *3 and *17 substitutions.

Results:

Results showed that heterozygotes and homozygotes of CYP2C19*2, *3 and *17 could be distinguished by the MGB blocker ARMS real-time PCR successfully. In the Chinese population, patients with allele frequencies of CYP2C19*2, *3, and *17 are 18.43%, 3.03% and 0.76%, respectively.

Conclusion:

This study indicates that the MGB blocker ARMS real-time PCR will be a simple, economical method for the rapid detection of SNPs in CYP2C19.

Evaluation of Tolerability, Pharmacokinetics and Pharmacodynamics of Vicagrel, a Novel P2Y12 Antagonist, in Healthy Chinese Volunteers

Background: Vicagrel is a novel anti-platelet drug and hydrolyzed to the same intermediate as clopidogrel via esterase, instead of CYP2C19. Here we report the first clinical trial on the tolerability, pharmacokinetics and pharmacodynamics of different doses of vicagrel, and comparison with clopidogrel in healthy Chinese volunteers. Methods: This study was conducted in two parts. Study I was a dose-escalating (5-15 mg) study. For each dose, 15 participants were randomized into three groups (total n = 45); nine participants were given vicagrel, three were given clopidogrel, and three were given a placebo. Study II was conducted to assess interactions between vicagrel and aspirin in 15 healthy participants. The plasma concentrations of the metabolites of vicagrel and clopidogrel were determined using a LC-MS/MS method. Platelet aggregation was assessed using the VerifyNow-P2Y12 assay. Results: Vicagrel (5-15 mg per day) dosing for 10 days or addition of aspirin was well tolerated in healthy volunteers. The exposure of the active metabolite increased proportionally across the dose range and was higher (~10-fold) than clopidogrel. The levels of IPA dosing 75 mg clopidogrel were between the responses of 5 mg and 10 mg vicagrel. After a single loading dose of vicagrel (30 mg) and a once-daily maintenance dose (7.5 mg) for 8 days, the maximum inhibition of platelet aggregation was similar to that seen with the combined use of vicagrel and aspirin (100 mg/day). Conclusion: Oral vicagrel demonstrated a favorable safety profile and excellent anti-platelet activity, which could be a promising P2Y12 antagonist as anti-platelet drug and can be further developed in phase II/III studies, and marketing for the unmet medical needs of cardiovascular diseases. The study was registered at http://www.chictr.org.cn (ChiCTR-IIR-16009260).

Exploring the nature of the clopidogrel–bromocresol green interactionviaspectrophotometric measurements and quantum chemical calculations

Clopidogrel is an oral, thienopyridine class antiplatelet agent used to inhibit blood clots in coronary arteries, peripheral vascular and cerebrovascular diseases. A spectrophotometric method was developed for clopidogrel bisulfate (CLOP·H₂SO₄) determination using bromocresol green (BCG) as an ion-pairing agent. To explore the binding nature of CLOP·H₂SO₄ with BCG at a molecular level, quantum chemical calculations have been performed. DFT based full geometry optimization has been carried out for BCG and clopidogrel in basic (CLOP) and protonated (CLOP⁺) forms as well as for BCG ion-pairs with CLOP and CLOP·H₂SO₄. The DFT calculations referred to the stability of the BCG–CLOP⁺ ion-pair and its spontaneous formation reaction from BCG and CLOP·H₂SO₄ compared to the BCG–CLOP-ion-pair. Furthermore, the UV-visible spectra and their corresponding excited states and electronic transitions for BCG, BCG–CLOP⁺ ion-pair, and BCG–CLOP ion-pair have been investigated. These spectra provided a molecular level understanding of the nature of the different intra-molecular and intermolecular electronic transitions in the BCG ion-pairs with CLOP⁺. Moreover, the quantitative analysis based on extracting a yellow-formed ion-pair into chloroform from aqueous medium was carried out. The ion-pair exhibits an absorption maximum at 413 nm. The optimum conditions of the reactions were studied experimentally and optimized. The calibration graph shows that CLOP·H₂SO₄ can be determined up to 100.0 μg mL⁻¹ with detection limit (LOD) of 0.57 μg mL⁻¹ and quantification limit (LOQ) of 1.86 μg mL⁻¹. The low relative standard deviation values, 0.16–1.16, indicate good precision. The results were compared to other published data and were treated statistically using F and t-tests.

The nature of the different electronic transitions of clopidogrel bisulfate; antiplatelet agent, in BCG ion-pair and quantitative analysis based on extracting a yellow-formed ion-pair into chloroform from aqueous medium is obtained.

Clopidogrel Response Variability: Review of the Literature and Practical Considerations

Dual antiplatelet therapy with aspirin and a P2Y12 inhibitor is standard therapy following acute coronary syndrome and percutaneous coronary intervention. Despite the use of potent antiplatelet agents, vascular events continue to occur. Lack of response to clopidogrel therapy has been widely investigated using various methods of platelet function testing. These studies have consistently found an association between poor clopidogrel response and an increased risk of vascular events. Strategies to overcome this problem include higher clopidogrel doses or the use of an alternative P2Y12 agent. To date, the majority of studies investigating tailored antiplatelet therapy have failed to show any reduction in clinical events likely due to the low-risk population studied. Despite this lack of benefit from altering therapy, platelet function testing may be done in certain patient populations. Patients at high risk of deleterious outcomes from stent thrombosis may be an appropriate patient population for platelet function testing to ensure adequate response to therapy. In addition, emerging data suggests a potential role for platelet function testing to assess for bleeding risk. The purpose of this article is to review the key studies demonstrating response variability to clopidogrel therapy, strategies to overcome variability, and practical considerations for the clinician.

Ticagrelor: a review of its use in adults with acute coronary syndromes

Ticagrelor (Brilique™, Brilinta®), a cyclopentyl-triazolopyrimidine, is an orally active, reversible, and selective adenosine diphosphate (ADP) receptor antagonist indicated for use in patients with acute coronary syndromes (ACS). Ticagrelor has a faster onset of action and provides greater inhibition of platelet aggregation than clopidogrel. In the large well-designed, PLATO study in adult patients with ACS, 12 months' treatment with ticagrelor was more effective than clopidogrel in reducing the incidence of the primary composite endpoint of myocardial infarction, stroke, or cardiovascular (CV) death. Ticagrelor also reduced all-cause mortality relative to clopidogrel, although statistical significance of this was not confirmed in hierarchical testing. Benefit with ticagrelor was seen both in invasively and noninvasively managed patients. Ticagrelor was generally well tolerated and was not associated with an increased risk of major bleeding relative to clopidogrel. However, the incidences of non-coronary artery bypass grafting (CABG)-related bleeding, and major or minor bleeding, as well as some non-hemorrhagic adverse events, including dyspnea (usually of mild or moderate severity) and ventricular pauses (largely asymptomatic) were higher with ticagrelor. In addition, the ATLANTIC study showed that although pre-hospital administration of ticagrelor did not improve pre-percutaneous coronary intervention (PCI) coronary reperfusion in ACS patients relative to in-hospital administration, ticagrelor was safe in both instances, with no significant between-group differences in non-CABG-related major and minor bleeding events. Although further comparative studies with other antiplatelet agents, including prasugrel, are required to position it more definitively, current evidence indicates that ticagrelor is a useful option for the prevention of thrombotic CV events in ACS patients managed invasively or noninvasively.

Relationships between PON1 Q192R polymorphism and clinical outcome of antiplatelet treatment after percutaneous coronary intervention: a meta-analysis

This meta-analysis was performed to assess the relationships between the PON1 Q192R (rs662 T>C) polymorphism and the clinical outcome of antiplatelet treatment after percutaneous coronary intervention (PCI). A range of electronic databases were searched: Web of Science (1945-2013), the Cochrane Library Database (Issue 12, 2013), PubMed (1966-2013), EMBASE (1980-2013), CINAHL (1982-2013) and the Chinese Biomedical Database (CBM) (1982-2013) without language restrictions. Meta-analysis was conducted using the STATA 12.0 software. The crude odds ratio (OR) with their 95 % confidence interval (CI) were calculated. Six clinical cohort studies with a total number of 5,189 patients undergoing PCI for coronary heart disease were included. Our meta-analysis revealed that the PON1 Q192R polymorphism was correlated with an increased risk of major adverse cardiovascular events (MACE) in patients receiving antiplatelet treatment after PCI (C allele vs. T allele: OR = 1.22, 95 % CI 1.04-1.43, P = 0.014; CT+CC vs. TT: OR = 1.38, 95 % CI 1.03-1.86, P = 0.029; CC vs. TT: OR = 1.45, 95 % CI 1.05-1.99, P = 0.024; respectively), especially among Asians. Furthermore, we found significantly positive correlations between the PON1 Q192R polymorphism and the incidence of stent thrombosis in patients receiving antiplatelet treatment after PCI (C allele vs. T allele: OR = 1.42, 95 % CI 1.08-1.87, P = 0.011; CT+CC vs. TT: OR = 1.93, 95 % CI 1.01-3.67, P = 0.046; CC vs. TT: OR = 2.18, 95 % CI 1.09-4.35, P = 0.027; respectively). Our meta-analysis of clinical cohort studies provides evidence that the PON1 Q192R polymorphism may increase the risk of MACE and stent thrombosis in patients receiving antiplatelet treatment after PCI.

Complications of hip fracture surgery on patients receiving clopidogrel therapy

INTRODUCTION

Clopidogrel (Plavix(®)) may influence patient safety during fracture surgery. Our study examines the incidence of complications for patients undergoing hemiarthroplasty on clopidogrel therapy.

MATERIALS AND METHODS

All patients, who underwent hemiarthroplasty between 2005 and 2011 were retrospectively reviewed. Patients were placed in two comparative groups based on the use of clopidogrel antiplatelet therapy. Records were reviewed for patient demographics, ASA score, pre and postoperative hemoglobin, time to surgery, length of stay, bleeding events, transfusions and complications. Comparative statistical analysis was performed using Fisher's exact test and Student's t test, using P < 0.05 to identify statistical significance.

RESULTS

A total of 203 charts were reviewed, of which 162 patients met inclusion/exclusion criteria. One hundred and twelve females and 50 males with mean age of 84 years were identified. The clopidogrel group consisted of 15 (9.3 %) patients and the nonclopidogrel group 147 (90.7 %). The clopidogrel group had more comorbidities resulting in a significantly higher ASA score (3.9 vs. 2.9), and lower preoperative hemoglobin (11.3 vs. 12.0). There was no significant difference identified in time to surgery, intraoperative blood loss, hemoglobin on days 1-3, or number of transfusions received between groups. Patients on clopidogrel were seen to have significantly longer hospital stays (10.6 vs. 7.4 days). However, a similar rate of wound and bleeding related complications (6.7 vs. 6.1 %) was seen.

CONCLUSIONS

The optimal treatment for hip fracture patients on antiplatelet therapy is unclear. However, in this study there appears to be no significant difference with regards to bleeding and bleeding related wound complications, suggesting it is safe to proceed with hemiarthroplasty for patients receiving clopidogrel.

Bi(OTf)3-catalyzed three-component synthesis of α-amino acid derivatives

A highly efficient Bi(OTf)3-catalyzed multicomponent synthesis of arylglycines from readily available starting materials is described. The reaction proceeds under mild conditions and provides a general route to various N-protected arylglycines.

Reversal of thienopyridine-induced platelet dysfunction following desmopressin administration

Adenosine diphosphate (ADP)-receptor antagonists are widely used for thrombus prevention, although reversing their platelet dysfunction is difficult. This study evaluated the ability of desmopressin to reverse clopidogrel-induced platelet dysfunction. Sprague-Dawley rats received either clopidogrel (30 mg/kg) or placebo, followed 4 h later by saline or desmopressin (0.15, 0.3, or 0.6 μg/kg). Bleeding times and platelet aggregation studies were subsequently performed. A bleeding time >25 min was considered "prolonged." The median bleeding time for clopidogrel-exposed rats was 21 min, vs. 6 min for controls (p < 0.01). Progressively higher doses of 1-deamino-8-D-arginine vasopressin (DDAVP) were associated with a reduced number of rats with prolonged bleeding time (p = 0.001). Higher doses of DDAVP were also associated with a reduction in the median (IQR) bleeding time; 29 (13.5-30) min in rats receiving clopidogrel without DDAVP vs. 19 (12-28) min in rats receiving clopidogrel and 0.6 μg/kg DDAVP. The step-wise dosing of DDAVP resulted in a 54 % reduction in meeting the endpoint of prolonged bleeding time (OR 0.46; p = 0.025; 95 % CI 0.23-0.91). Platelet aggregation was observed in all control rats, but only some of those clopidogrel-treated rats who received 0.6 μg/kg DDAVP. In this model of an ADP-receptor antagonist, DDAVP results in partial reversal of clopidogrel-induced platelet dysfunction.

Clopidogrel dilemma for orthopaedic surgeons

BACKGROUND

Patients medicated with clopidogrel who require orthopaedic surgery present a particular challenge. Whether in an emergency or elective situation the orthopaedic surgeon must balance the risks of ceasing clopidogrel versus the risk of increased bleeding that dual antiplatelet therapy generates.

METHOD

This paper reviews the current published evidence regarding the risks of continuing clopidogrel, the risks of discontinuing clopidogrel and associated considerations such as venous thromboprophylaxis.

RESULTS

Little good quality evidence exists in regard to perioperative clopidogrel for orthopaedic surgery. Available evidence across non-cardiac and cardiac surgery were assessed and presented in regards to current practices, blood loss for orthopaedic operations, risks when continuing clopidogrel, risks of stopping clopidogrel and also the consideration of venous thromboembolism.

CONCLUSIONS

The patients at greatest risk, when discontinuing clopidogrel therapy, are those with drug eluting stents who may be at risk of stent thrombosis. Where possible, efforts should be made to continue clopidogrel therapy through the perioperative period, taking precautions to minimize bleeding. If the risk of bleeding is too high, antiplatelet therapy must be reinstated as soon as considered reasonable after surgery. In addition, patients on clopidogrel who sustain a fall or other general trauma need to be carefully assessed because of the possibility of occult bleeding, such as into the retroperitoneal space. Until more definitive evidence becomes available, this review aims to provide a guide for the orthopaedic surgeon in dealing with the difficult dilemma of the patient on clopidogrel therapy, recommending that orthopaedic surgeons take a team approach to assess the individual risks for all patients and consider continuation of clopidogrel therapy perioperatively where possible.

Ticagrelor: oral reversible P2Y(12) receptor antagonist for the management of acute coronary syndromes

BACKGROUND

The clinical benefits of dual antiplatelet treatment (aspirin + clopidogrel) in the management of acute coronary syndromes (ACS) are well established. However, clopidogrel is a prodrug that requires hepatic activation. Concerns regarding its delayed onset of action, variability in antiplatelet effects, and prolonged recovery of platelet function after discontinuation have prompted the development of P2Y(12) receptor antagonists. Ticagrelor is the most recently developed P2Y(12) receptor antagonist available in the United States. Ticagrelor is a nonthienopyridine antiplatelet agent and is the first reversible oral antagonist of the P2Y(12) receptors.

OBJECTIVE

This article reviews the pharmacology, clinical efficacy, and tolerability of ticagrelor use in management of ACS.

METHODS

Peer-reviewed clinical trials, review articles, and relevant treatment guidelines published from 1966 to March 15, 2012, were identified from the MEDLINE and Current Content databases using the search terms ticagrelor, ACS, pharmacokinetics, pharmacodynamics, pharmacoeconomics, and cost-effectiveness. Citations from available articles were also reviewed for additional references.

RESULTS

Nine pharmacokinetics/pharmacodynamics studies in humans and 1 clinical study were identified. In addition, the findings from 6 subanalyses based on the clinical study were included. Compared with clopidogrel, ticagrelor was associated with a significantly reduced composite rate of death from cardiovascular causes, myocardial infarction, or stroke (ticagrelor, 9.8%; clopidogrel, 11.7%; hazard ratio [HR] = 0.84; 95% CI, 0.77-0.92; P < 0.001). The difference in the rates of major bleeding was not significant (ticagrelor, 11.6%; clopidogrel, 11.2%). Ticagrelor was associated with a higher rate of non-coronary artery bypass graft surgery related major bleeding (4.5% vs 3.8%; P = 0.03), including fatal intracranial bleeding (0.1% vs 0.01%; P = 0.02), and fewer cases of other types of fatal bleeding (0.1% vs 0.3%; P = 0.03). Other adverse events reported with ticagrelor use included dyspnea (13.8%), headache (6.5%), and bradyarrhythmia (5.8%). The effects of ticagrelor have not been compared to those of other antiplatelet agents, including prasugrel.

CONCLUSIONS

Based on the findings from the present review, ticagrelor provides reversible inhibition of adenosine diphosphate-induced platelet aggregation, with a faster onset of action than clopidogrel, and is effective in the treatment of patients with ACS. More data are required to definitively position ticagrelor with respect to other antiplatelet agents, including prasugrel.

Capillary zone electrophoresis method for determination of (+)-S clopidogrel carboxylic acid metabolite in human plasma and urine designed for biopharmaceutic studies

Fast and reproducible Capillary Zone Electrophoresis (CZE) method for the quantification of (+)-S clopidogrel carboxylic acid metabolite in human fluids was elaborated for the first time. Optimal buffer and CZE conditions were established to obtain the complete separation of clopidogrel, its metabolite and piroxicam (internal standard), during one analytical run. Finally, resolution of the analytes was obtained in an uncoated silica capillary filled with a phosphate buffer of pH 2.5. The analytes were isolated from plasma and urine samples using solid phase extraction (SPE). Validation of the CZE method was carried out. The calibration curve of clopidogrel was linear in the range of 0.5-10.0mg/L in plasma and urine, whereas for (+)-S carboxylic acid metabolite linearity was confirmed in the range of 0.25-20.0mg/L in plasma and 0.25-10.0mg/L in urine. Intra- and inter-day precision and accuracy were repeatable. LOD and LOQ were also estimated. SPE recovery of the analytes from plasma and urine was comparable and greater than 80%. The validated method was successfully applied in pharmacokinetic investigations of (+)-S carboxylic acid metabolite of clopidogrel following the oral administration of clopidogrel to patients prior to percutaneous coronary intervention.

Case files of the Medical Toxicology Fellowship at Banner Good Samaritan Medical Center in Phoenix, AZ: a non-warfarin anticoagulant overdose

A 50-year-old man presented to the emergency department (ED) following an overdose of his "blood thinners." The patient had become increasingly depressed over financial concerns, prompting a suicide attempt. He declined to provide any details regarding his current medications or his past medical history. A review of the computerized medical record, however, revealed he had a Factor V Leiden mutation with multiple venothromboembolic events. He previously had an inferior vena cava filter placed, and had received tissue plasminogen activator (tPA) for a cerebrovascular accident. A toxicology consult was obtained in the ED.

Clopidogrel pharmacogenomics and risk of inadequate platelet inhibition: US FDA recommendations

Antiplatelet therapy with clopidogrel is the current standard of care for coronary artery disease patients undergoing a percutaneous coronary intervention. However, approximately 25% of patients experience a subtherapeutic antiplatelet response. Clopidogrel is a prodrug that undergoes hepatic biotransformation by CYP2C19 into its active metabolite. Several studies have reported that, compared with wild-type individuals, CYP2C19 variant allele carriers exhibit a significantly lower capacity to metabolize clopidogrel into its active metabolite and inhibit platelet activation, and are therefore at significantly higher risk of adverse cardiovascular events. Consequently, the US FDA has recently changed clopidogrel's prescribing information to highlight the impact of CYP2C19 genotype on clopidogrel pharmacokinetics, pharmacodynamics and clinical response. Future studies remain necessary to develop effective personalized therapeutic strategies for CYP2C19 variant allele carriers and other individuals at risk for clopidogrel nonresponsiveness.

Cardiovascular event rates in patients with cerebrovascular disease and atherothrombosis at other vascular locations: results from 1-year outcomes in the Japanese REACH Registry

The REduction of Atherothrombosis for Continued Health (REACH) Registry is a large, international, prospective cohort of patients with atherothrombosis or multiple (>or=3) risk factors (MRFs) for atherothrombosis. Japanese patients (n=5193) were enrolled into the REACH registry between August and December 2004. One-year event rate in patients with cerebrovascular disease (CVD) was compared with that of patients with symptomatic atherothrombosis at other locations. After one year (n=5021), patients with CVD (n=1962) experienced a higher rate of non-fatal strokes than patients with coronary artery disease (CAD), peripheral artery disease (PAD) or MRFs alone (2.77% vs. 1.28%, 2.07% and 1.56%, respectively), but a lower rate of non-fatal myocardial infarction (0.45% vs. 1.31%, 0.77% and 0.66%, respectively). Patients with CVD plus disease in >or=1 other vascular bed had higher rates of cardiovascular events than patients with CVD alone. Overall, event rates including non-fatal stroke, non-fatal myocardial infarction and cardiovascular death were higher for patients with CVD and PAD than for patients with CVD and CAD. Asymptomatic carotid stenosis >or=70% and ankle-brachial index <0.9 were significant predisposing factors for stroke. Patients with CVD and co-existing atherothrombotic diseases had a high risk of recurrent events, including events arising in other vascular beds than originally diagnosed.

Cost effectiveness of fondaparinux in non-ST-elevation acute coronary syndrome

BACKGROUND

Fondaparinux has been shown to reduce the risk of major bleeding and 30-day mortality compared with enoxaparin, in patients with non-ST-elevation acute coronary syndrome (NSTE-ACS). However, its cost effectiveness is not well known.

OBJECTIVE

To evaluate the effectiveness and economic attractiveness of fondaparinux relative to enoxaparin in patients with NSTE-ACS treated with triple antiplatelet therapy and early (non-urgent) invasive strategy.

METHODS

The decision model compares two alternative strategies: subcutaneous (SC) enoxaparin (1 mg/kg 12 hourly) versus SC fondaparinux (2.5 mg/day) in NSTE-ACS patients pre-treated with triple antiplatelet therapy and early revascularization. Cost-effectiveness and cost-utility analyses were performed from a healthcare perspective, based on a Markov model with a time horizon of the patient lifespan. Univariate sensitivity analysis and probabilistic (Monte Carlo) microsimulation analysis were performed.

RESULTS

In the base-case analysis (65 years, Thrombolysis In Myocardial Infarction [TIMI] score 4), the use of fondaparinux was associated with a significant reduction in major bleeding, a slight reduction in adverse cardiac events, and minor improvements in survival and QALYs, together with a small reduction in costs. The dominance of fondaparinux over enoxaparin remained unchanged in the univariate sensitivity analyses. According to Monte Carlo simulation, fondaparinux was cost saving in 99.9% of cases.

CONCLUSION

Compared with enoxaparin, the use of fondaparinux in patients with NSTE-ACS managed with an early invasive strategy appears to be cost effective, even in patients with a low risk of bleeding.

Why is the use of clopidogrel increasing rapidly in Australia? An exploration of geographical location, age, sex and cardiac stenting rates as possible influences on clopidogrel use

PURPOSE

To explore clopidogrel use within Australia, investigating geography, age, sex and cardiac stenting rates.

METHODS

Data for clopidogrel supply (Pharmaceutical Benefits Scheme (PBS) and Repatriation Pharmaceutical Benefits Scheme (RPBS)) and cardiac stenting procedures (State Health Departments) were obtained for four different geographic regions (very remote/remote and major city in two Australian states). General linear modelling and correlation analyses were used to test for associations and chi2 analyses for proportions.

RESULTS

Clopidogrel supply increased rapidly in Australia since introduction, from 1.2 to 9.0 Defined Daily Doses (DDD)/1000 population/day. Among concessional and veteran populations use was much higher. Analysis of geographical area data confirmed an association between clopidogrel supply rates and cardiac stenting rates (r = 0.8-0.9 Spearman's rho, p < 0.01). Sex, age and geographical location were associated with both rates when considered together and when considered independently. Further modelling indicated that between 30 and 73% of clopidogrel supply could be accounted for by people receiving cardiac stents.

CONCLUSIONS

The supply of clopidogrel increases with age, male sex and living in a major city. These same demographic variables were important for cardiac stenting, an indication which is currently not approved for subsidy by the Australian government, but which modelling indicated could account for between one-third and three quarters of clopidogrel use. A review may be required to ensure subsidised indications reflect current evidence and cost-effective use.

The GPIIb/IIIa (integrin alphaIIbbeta3) odyssey: a technology-driven saga of a receptor with twists, turns, and even a bend

Starting 90 years ago with a clinical description by Glanzmann of a bleeding disorder associated with a defect in platelet function, technologic advances helped investigators identify the defect as a mutation(s) in the integrin family receptor, alphaIIbbeta3, which has the capacity to bind fibrinogen (and other ligands) and support platelet-platelet interactions (aggregation). The receptor's activation state was found to be under exquisite control, with activators, inhibitors, and elaborate inside-out signaling mechanisms controlling its conformation. Structural biology has produced high-resolution images defining the ligand binding site at the atomic level. Research on alphaIIbbeta3 has been bidirectional, with basic insights resulting in improved Glanzmann thrombasthenia carrier detection and prenatal diagnosis, assays to identify single nucleotide polymorphisms responsible for alloimmune neonatal thrombocytopenia, and the development of alphaIIbbeta3 antagonists, the first rationally designed antiplatelet agents, to prevent and treat thrombotic cardiovascular disease. The future looks equally bright, with the potential for improved drugs and the application of gene therapy and stem cell biology to address the genetic abnormalities. The alphaIIbbeta3 saga serves as a paradigm of rigorous science growing out of careful clinical observations of a rare disorder yielding both important new scientific information and improved diagnosis, therapy, and prevention of other disorders.