Clopidogrel Activation

Clopidogrel - Wikipedia

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As clopidogrel is metabolized by the liver enzyme CYP2C19, in cellular models it has been theorized that it might increase blood plasma levels of other drugs that are metabolized by this enzyme, such as phenytoin and tolbutamide. Clinical studies showed that this mechanism is irrelevant for practical purposes. In 2010, the US Food and Drug Administration (FDA) added a boxed warning, later updated, to Plavix, alerting that the drug can be less effective in people unable to metabolize the drug to convert it to its active form. CYP2C19 is an important drug-metabolizing enzyme that catalyzes the biotransformation of many clinically useful drugs, including antidepressants, barbiturates, proton-pump inhibitors, and antimalarial and antitumor drugs. Clopidogrel is one of the drugs metabolized by this enzyme. People with variants in cytochrome P-450 2C19 (CYP2C19) have lower levels of the active metabolite of clopidogrel, less inhibition of platelets, and a 3.58-times greater risk for major adverse cardiovascular events such as death, heart attack, and stroke; the risk was greatest in CYP2C19 poor metabolizers. A published review showed that some mutations of CYP2C19, CYP3A4, CYP2C9, CYP2B6, and CYP1A2 genes could affect the clinical efficacy and safety of clopidogrel treatment. The active form specifically and irreversibly inhibits the P2Y12 subtype of ADP receptor, which is important in activation of platelets and eventual cross-linking by the protein fibrin. After repeated oral doses of 75 mg of clopidogrel (base), plasma concentrations of the parent compound, which has no platelet-inhibiting effect, are very low and, in general, are below the quantification limit (0.258 μg/L) beyond two hours after dosing. Clopidogrel is a prodrug, which is activated in two steps, first by the enzymes CYP2C19, CYP1A2, and CYP2B6, then by CYP2C19, CYP2C9, CYP2B6, and CYP3A. The thiophene ring is converted to a thiolactone. This thiolactone is then oxidized by a cytochrome P450 into a thiolactone S-oxide, that is unstable and opens in water to a sulfenic acid.

Activation and mechanism of action of clopidogrel. After ...

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Download scientific diagram | Activation and mechanism of action of clopidogrel. After absorption, the clopidogrel (inactive) is oxidized to 2-oxo clopidogrel (still inactive, too) by cytochrome P450 (CYP) enzymes in the liver. The 2-oxo clopidogrel is then transformed into active thiol metabolites that will bind to, and inhibit, the ADP P2RY12 receptor (adenosine diphosphate purinergic receptor P2Y G protein–coupled 12) on platelet surfaces. Clopidogrel and aspirin are among the most prescribed dual antiplatelet therapies to treat the acute coronary syndrome and heart attacks. However, their potential clinical impacts are a subject of intense debates. Objective: Conflicting data exist as to whether proton-pump inhibitors (PPIs) diminish the efficacy of clopidogrel. The aim of this study was to investigate the association between cytochrome P450 (CYP) genetic variants and clinical adverse outcomes of concomitant use of PPIs and clopidogrel by patients. Polymorphisms in drug metabolism enzyme [cytochrome P450 (CYP) family] genes are independent factors for the variability in response to clopidogrel. However, a sex-specific impact of genetics to explain worse clinical outcomes in women has not been extensively explored.

What is the mechanism of action of Plavix (clopidogrel)?

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This irreversible nature allows for once-daily dosing despite the short half-life of the active metabolite 2 · 5-10% of patients are completely resistant to clopidogrel's effects 5 · Up to 25% of patients show only partial responsiveness 5 ... Medications that inhibit CYP450 enzymes (particularly CYP2C19) may reduce clopidogrel's effectiveness 4 · Proton pump inhibitors (especially omeprazole) have been studied for potential interactions, though clinical significance remains debated 4 Clopidogrel works by irreversibly binding its active metabolite to the P2Y12 adenosine diphosphate (ADP) receptor on platelets, thereby inhibiting platelet activation and aggregation. The irreversible nature of clopidogrel's binding explains several important clinical characteristics: Once-daily dosing is effective despite short half-life 2 · Platelet function takes 5-7 days to normalize after discontinuation 1 · Loading doses (300-600 mg) are used to achieve faster onset of action in acute settings 5 · Patients requiring surgery should ideally discontinue clopidogrel 5-7 days prior to reduce bleeding risk 1 · Understanding clopidogrel's mechanism helps explain why laboratory monitoring of its effect requires specific platelet function tests that measure ADP-induced aggregation rather than general coagulation tests. antiplatelet drugs: antithrombotic therapy and prevention of thrombosis, 9th ed: american college of chest physicians evidence-based clinical practice guidelines. ... What is the recommended dose of benzonatate for an adult patient with acute cough and a history of cardiovascular disease, currently taking Plavix (clopidogrel)?

Clopidogrel - an overview | ScienceDirect Topics

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Recognizing that genetic tests are becoming increasingly widespread CPIC provides peer-reviewed guidelines aiding to facilitate the translation of genetic test results into clinical decision making. For patients undergoing PCI who are also carriers of the CYP2C19 loss-of-function alleles, the CPIC recommends use of alternative therapies such as prasugrel or ticagrelor (Scott et al., 2011). ... Clopidogrel is a thienopyridine derivative that selectively inhibits the binding of adenosine diphosphate to its platelet receptor and the subsequent adenosine diphosphate–mediated activation of the glycoprotein IIb/IIIa complex, thereby inhibiting platelet aggregation. It is a prodrug that requires conversion to its active metabolite by the cytochrome P450 system before it exerts its antiplatelet effects. The lack or diminished antiplatelet response in a substantial number of patients receiving clopidogrel is a major problem during its clinical use. Wide interindividual variability in the degree of inhibition of ADP-induced platelet function has been observed among patients treated with clopidogrel; so-called “high on-treatment platelet reactivity” (HPR) is reported in up to 35% of patients.53 The mechanisms for this variability are likely multifactorial, including drug, environmental, and genetic interactions. Clopidogrel's action depends on biotransformation to its active metabolite in the liver, largely by CYP2C19, and studies have linked the presence of CYP2C19 loss-of-function alleles, such as CYP2C19*2, with an increased risk of There was an increase in major bleeding but no significant excess of life-threatening bleeding. The investigators concluded that, overall, the benefits of starting clopidogrel on admission appeared to outweigh the risks, even among those who proceeded to CABG during the initial hospitalization. The Clopidogrel as Adjunctive Reperfusion Therapy –Thrombolysis in Myocardial Infarction (CLARITY-TIMI) 28 study tested the effect of clopidogrel on angiographic and clinical outcome among patients younger than 75 years with STEMI who were treated with standard fibrinolytic therapy.46 Patients were randomly assigned to receive 300 mg of clopidogrel coincident with the fibrinolytic agent followed by 75 mg/day or placebo; angiographic infarct-related artery patency and adverse events were assessed at 2 to 8 days.

Clopidogrel pathway - PMC - NIH

pmc.ncbi.nlm.nih.gov

Several publications indicate a major role for CYP3A4 [6,7]. Other in-vitro studies showed that CYP1A2, CYP2B6, and CYP2C19 were capable of forming the 2-oxo-clopidogrel form from clopidogrel in liver microsomes [8,9]. When 2-oxo-clopidogrel was used as a substrate, the enzymes CYP3A4, CYP2C9, CYP2C19, and CYP2B6 produced the active metabolite [8,9]. The study by Kazui et al. [9] concluded that CYP2C19 contributes substantially to both oxidative steps and that CYP3A4 contributes substantially to the second oxidative step. ... Representation of the candidate genes involved in the metabolism of clopidogrel and its primary mechanism of action. The CYP2C19*2 genetic variant, 681 G > A (rs4244285), was identified as a major determinant of prognosis in young patients who received clopidogrel treatment after myocardial infarction [29]. Furthermore, patients carrying any two CYP2C19 loss-of-function alleles [*2, *3 (rs4986893), *4 (rs28399504), or *5 (rs56337013)] had a higher rate of cardiovascular events than patients who did not have these alleles [24]. Similarly, another study showed that carriers of a reduced-function CYP2C19 allele had significantly lower levels of clopidogrel’s active metabolite, diminished platelet inhibition, and a higher rate of major adverse cardiovascular events [30]. A genome-wide association analysis identified 13 SNPs on chromosome 10q24 within the CYP2C18-CYP2C19-CYP2C9-CYP2C8 cluster showing strong evidence for association with clopidogrel response in an Amish population. Genetic determinants of response to clopidogrel and cardiovascular events. N Engl J Med. 2009;360:363–375. doi: 10.1056/NEJMoa0808227. [DOI] [PubMed] [Google Scholar] 25.Shuldiner AR, O’Connell JR, Bliden KP, Gandhi A, Ryan K, Horenstein RB, et al. Association of cytochrome P450 2C19 genotype with the anti-platelet effect and clinical efficacy of clopidogrel therapy. Recent studies indicate that the pharmacodynamic response to clopidogrel is variable, with 20–40% of patients being classified as nonresponders, poor responders or resistant to clopidogrel because of low inhibition of ADP-induced platelet aggregation or activation [21]. Nongenetic factors influencing the clopidogrel response include age, diabetes, renal failure, and cardiac failure [22]. As described above, the prodrug clopidogrel requires activation in the liver.

What is the mechanism of Clopidogrel Bisulfate?

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In summary, the mechanism of clopidogrel bisulfate involves its conversion into an active metabolite by liver enzymes, which then irreversibly inhibits the P2Y12 receptor on platelets, preventing ADP-mediated platelet activation and aggregation. This inhibition helps reduce the risk of thrombotic cardiovascular events in susceptible patients. Understanding the pharmacodynamics and pharmacogenetics of clopidogrel can optimize its use and enhance patient outcomes in clinical practice.