Pretreatment with antiplatelet drugs improves the cardiac function after myocardial infarction without reperfusion in a mouse model.

BACKGROUND: Reperfusion therapy is known to improve prognosis and limit myocardial damage after myocardial infarction (MI). The administration of antiplatelet drugs prior to percutaneous coronary intervention also proves beneficial to patients with acute MI (AMI). However, a good number of AMI patients do not receive reperfusion therapy, and it is not clear if they would benefit from antiplatelet pre-treatment. METHODS: Experimental C57BL/6 mice were randomly allocated to five groups: the sham group, control, post-treatment, pre-treatment, and pre- and post-treatment groups. Acetylsalicylic acid (15 mg/kg), clopidogrel (11 mg/kg), ticagrelor (27 mg/kg), and prasugrel (1.5 mg/kg) were intragastrically administered in the treatment groups. On day 7 post MI, cardiac function and cardiac fibrosis were evaluated using echocardiography and Masson's trichrome staining, respectively. Histopathological examinations were performed on tissue sections to grade inflammatory cell infiltration. Platelet inhibition was monitored by measuring thrombin-induced platelet aggregation. RESULTS: Left ventricular ejection fraction and fractional shortening improved significantly (p < 0.01) in the pre-treatment groups when compared to the post-treatment and control groups. A significant (p < 0.01) decrease in cardiac fibrosis was observed in the pre-treatment group, compared with the posttreatment and control groups. Inflammatory cell infiltration significantly decreased in the pre-treatment group compared with the control group (p < 0.05). Thrombin-induced platelet aggregation was significantly inhibited by antiplatelet drugs, but increased with the exposure to H2O2. CONCLUSIONS: In the absence of reperfusion therapy, pre-treatment with antiplatelet drugs successfully improved cardiac function, reduced cardiac fibrosis and inflammatory cell infiltration, and inhibited oxidative stress-induced platelet aggregation after MI in the mouse model.

Univariate and Multivariate Models for Determination of Prasugrel Base in the Formulation of Prasugrel Hydrochloride Using XRPD Method.

Prasugrel hydrochloride (PHCl) undergoes salt disproportionation, and the resulting prasugrel free base (PFB) may lead to the poor in vitro and or in vivo performance of the drug product. The aim of the present work was to develop univariate and multivariate models based on X-ray powder diffraction to quantify the salt and base in the powder and tablet formulations. Compositionally identical formulations of PHCl and PFB were prepared and mixed in various proportions to make 0%-30% PFB sample matrices. The formulations consisted of commonly used excipients, which are generally used in commercially available products. X-ray powder diffraction data were collected and subjected to the least square regression and partial least square regression analysis. The model performance parameters such as root mean squared and standard errors were low for univariate models compared to partial least square regression multivariate models. Model predicted values of the independent sample matrices by both methods matched closely with the actual values of PFB and PHCl. However, residual and standard deviation were low in univariate models predicted values. The models developed in this work have been shown to quantitate the PHCl disproportionation to PFB fraction in the drug product and provide a means to control the disproportionation of PHCl.

The Degradation Chemistry of Prasugrel Hydrochloride: Part 1-Drug Substance.

Prasugrel hydrochloride is the active ingredient in Effient™, a thienopyridine platelet inhibitor. An extensive study of the degradation chemistry of prasugrel hydrochloride (LY640315 hydrochloride) has been carried out on the drug substance (part I) and on the drug product (part II, future article) using a multidimensional approach including hydrolytic, oxidative, and photolytic stressing, computational chemistry, HPLC analysis, and structure elucidation by various spectroscopic techniques. The major degradation products formed from the drug substance under the various stress conditions have been isolated and structures unambiguously determined, and the pathways leading to these products have been proposed. Fourteen new (not previously disclosed) products were discovered and characterized, in addition to 4 degradation products that had been previously identified in the literature. The pathways indicate that prasugrel is susceptible to hydrolysis, autoxidation (both radical-initiated and single-electron mediated), and peroxide-mediated oxidation; in solution, prasugrel is susceptible to photodegradation.

Utility of Physiologically Based Pharmacokinetic Absorption Modeling to Predict the Impact of Salt-to-Base Conversion on Prasugrel HCl Product Bioequivalence in the Presence of Proton Pump Inhibitors.

Prasugrel HCl may convert to prasugrel base during manufacturing or storage. It was reported that formulations with different ratios of salt to base were bioequivalent in healthy subjects, but formulations with a higher extent of conversion were not bioequivalent in subjects taking proton pump inhibitor (PPI) whose stomach pH is elevated. The objective of this study was to assess the magnitude of impact of salt-to-base conversion on prasugrel HCl products BE evaluation in healthy subjects on PPI. A physiologically based pharmacokinetic (PBPK) absorption model was constructed to predict pharmacokinetic (PK) profiles of active metabolite after oral administration of prasugrel HCl products containing various fractions of base based on the prasugrel salt and base intrinsic solubility. The intrinsic solubility was obtained by deconvoluting the model against the observed active metabolite PK profiles with various fractions of base in healthy subjects with or without PPI. The developed PBPK absorption model accurately predicted the average active metabolite PK profiles in healthy subjects without PPI for the product containing 100% salt. A model based on assumptions of the fraction of a dose absorbed remaining unchanged for formulations containing different fractions of base over predicted the reduction of bioavailability upon conversion to the base. Therefore, this represented the conservative estimate with respect to the impact of free base in a product on BE evaluation. Virtual BE trial simulation predicted that less than 20% free base in prasugrel HCl product ensures in vivo BE of the generic product including in subjects that may be taking PPI.

Development of novel prasugrel base microsphere-loaded tablet with enhanced stability: Physicochemical characterization and in vivo evaluation in beagle dogs.

The objective of this study was to develop a novel prasugrel base microsphere-loaded tablet (PBMST) with enhanced stability as a bioequivalent to the commercial prasugrel hydrochloride-loaded tablet. Numerous prasugrel base-loaded microspheres were prepared with hydroxypropylmethyl cellulose (HPMC), colloidal silica and various acidifying agents using a spray-drying process, and the physicochemical properties, solubility and stability were investigated. The PBMSTs were prepared and their dissolution, pharmacokinetics in beagle dogs and stability were evaluated compared to commercial prasugrel hydrochloride-loaded tablets. Among the acidifying agents tested, phosphoric acid provided the greatest increase in drug solubility, by as much as 110-fold. The prasugrel base-loaded microspheres composed of prasugrel base, HPMC, colloidal silica and phosphoric acid at a weight ratio of 10/10/5/2.5 provided an amorphous drug and reduced particle size of about 11.3µm. Moreover, it exhibited excellent solubility and improved stability compared to prasugrel base and hydrochloride. Moreover, PBMST drug dissolution was improved in comparison to the prasugrel base-loaded tablet (PBT), with similar dissolution to the commercial prasugrel hydrochloride-loaded tablet at pH 1.2 and 4.0. PBMST provided significantly higher plasma concentrations of AUC and Cmax in beagle dogs compared to PBT. In particular, the AUC of PBMST was approximately four times greater than PBT, leading to improved oral bioavailability. There were no significant differences observed for all pharmacokinetic parameters between PBMST and the commercial prasugrel hydrochloride-loaded tablet, suggesting their bioequivalence in beagle dogs. Furthermore, the prepared PBMSTs were stable for at least six months. Therefore, this novel prasugrel base microsphere-loaded tablet could be a potential alternative for enhancing the stability and bioavailability of prasugrel.

Synergistic effect of anti-platelet and anti-inflammation of drug-coated Co-Cr substrates for prevention of initial in-stent restenosis.

Antiplatelet and antithrombotic therapies are systematically considered to prevent restenosis following coronary stent implantation. Currently, patients receiving medicated stents are prescribed to orally take anticoagulants and antiplatelet drugs such as aspirin (ASP) and prasugrel (PRAS). Propolis (PROP) known as a natural organic compound was recently evaluated for its antiplatelet activity, antibiotics and immunomodulatory activities. In this study, antiplatelet drug-coated Co-Cr substrates were prepared with biodegradable poly(d,l-lactide) (PDLLA) containing ASP, PRA, or PROP using electrospray and the blood compatibility of the different substrates was investigated by measuring protein adsorption and platelet adhesion. In addition, the anti-inflammatory properties of the modified Co-Cr surfaces were assessed by measuring IL-8 and IL-6 expression levels in human endothelial cell cultures. Drug-coated surfaces were found to resist the adsorption of fibrinogen when compared to bare Co-Cr or PDLLA-coated Co-Cr. Interestingly, ASP- and PROP-containing substrates not only showed reduced adhesion of platelets and delayed coagulation time, but also drastically reduced the expression level of IL-8 and IL-6. Such results are supported that ASP- or PROP-coated Co-Cr can be potentially used as a stent material to mitigate early stage of restenosis. The developed coating materials might be an interesting alternative to systemic anticoagulant therapies prescribed after stent implantation.

Antiplatelet Agents in Cardiology: A Report on Aspirin, Clopidogrel, Prasugrel, and Ticagrelor.

Antiplatelet drugs are the cornerstone of therapy in many cardiovascular conditions. With the current success and increased use of transcatheter aortic valve implantation (TAVI), the use of antiplatelet therapy is considered part of the medical therapy for these patients. Clinicians caring for these patients need to have a thorough understanding of the pharmacology, pharmacokinetics, pharmacodynamic, and clinical efficacy and safety of commonly used antiplatelet therapy. While aspirin therapy is widely used, dual antiplatelet therapy with clopidogrel has become part of standard of care. Despite the extensive experience with clopidogrel, there are limitations such as drug interactions, metabolism genetic polymorphisms, and variability in the antiplatelet response. More predictable and more potent antiplatelet agents, prasugrel and ticagrelor, have demonstrated superior reductions in ischemic endpoints as part of dual antiplatelet therapy compared to clopidogrel, but at the cost of more major bleeding in patients with an acute coronary syndrome. Significant research needs to be conducted in the setting of TAVI to help define the optimal antiplatelet regimen.

Study of the forced degradation behavior of prasugrel hydrochloride by liquid chromatography with mass spectrometry and liquid chromatography with NMR detection and prediction of the toxicity of the characterized degradation products.

Prasugrel was subjected to forced degradation studies under conditions of hydrolysis (acid, base, and neutral), photolysis, oxidation, and thermal stress. The drug showed liability in hydrolytic as well as oxidative conditions, resulting in a total of four degradation products. In order to characterize the latter, initially mass fragmentation pathway of the drug was established with the help of mass spectrometry/time-of-flight, multiple stage mass spectrometry and hydrogen/deuterium exchange data. The degradation products were then separated on a C18 column using a stability-indicating volatile buffer method, which was later extended to liquid chromatography-mass spectrometry studies. The latter highlighted that three degradation products had the same molecular mass, while one was different. To characterize all, their mass fragmentation pathways were established in the same manner as the drug. Subsequently, liquid chromatography-nuclear magnetic resonance (NMR) spectroscopy data were collected. Proton and correlation liquid chromatography with NMR spectroscopy studies highlighted existence of diastereomeric behavior in one pair of degradation products. Lastly, toxicity prediction by computer-assisted technology (TOPKAT) and deductive estimation of risk from existing knowledge (DEREK) software were employed to assess in silico toxicity of the characterized degradation products.

Bioactivation of clopidogrel and prasugrel: factors determining the stereochemistry of the thiol metabolite double bond.

The antithrombotics of the tetrahydrothienopyridine series, clopidogrel and prasugrel, are prodrugs that must be metabolized in two steps to become pharmacologically active. The first step is the formation of a thiolactone metabolite. The second step is a further oxidation with the formation of a thiolactone sulfoxide whose hydrolytic opening leads to a sulfenic acid that is eventually reduced into the corresponding active cis thiol. Very few data were available on the formation of the isomer of the active cis thiol having a trans configuration of the double bond, the most striking result in that regard being that both cis and trans thiols were formed upon the metabolism of clopidogrel by human liver microsomes in the presence of glutathione (GSH), whereas only the cis thiol was detected in the sera of patients treated with this drug. This article shows that trans thiols are also formed upon the microsomal metabolism of prasugrel or its thiolactone metabolite in the presence of GSH and that metabolites having the trans configuration of the double bond are only formed when microsomal incubations are done in the presence of thiols, such as GSH, N-acetyl-cysteine, and mercaptoethanol. Intermediate formation of thioesters resulting from the reaction of GSH with the thiolactone sulfoxide metabolite appears to be responsible for trans thiol formation. Addition of human liver cytosol to the microsomal incubations led to a dramatic decrease of the formation of the trans thiol metabolites. These data suggest that cytosolic esterases would accelerate the hydrolytic opening of thiolactone sulfoxide intermediates and disfavor the formation of thioesters resulting from the reaction of these intermediates with GSH that is responsible for trans isomer formation. This would explain why trans thiols have not been detected in the sera of patients treated with clopidogrel.

Isolation and Structural Elucidation of an Unknown Impurity in Prasugrel by Semi-Preparative Liquid Chromatography.

A brand-new impurity was detected by RP-HPLC in the prasugrel. The impurity was named as Impurity X. Impurity X was isolated by using semi-preparative HPLC followed by characterization using nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry. The functional mechanism of Impurity X was speculated. Impurity X could be controlled in the manufacture process of the prasugrel active pharmaceutical ingredient effectively.