Oral Administration Of Clopidogrel Research Articles

Study of influence of surface-active substances concentration on clopidogrel releasing from the rectal suppository

During the last years clopidogrel which together with strong polyvalent antiaggregatory action on platelets decreases the level of triglycerides and optimizes other indexes of lipidogramm has ranked the leading place from the medications with antiplatelet mechanism. In the Ukrainian pharmaceutical market clopidogrel is presented in form of domestic and imported film-coated tablets. Alternative to oral administration of clopidogrel is rectal route which thanks to increasing of medical substance bioavailability allows to decrease the active ingredient dose and minimize the risks of unwanted side effects in the organism. At the Medicinal Preparations Technology Department of Zaporozhye State Medical University the research of composition development and technology of clopidogrel rectal dosage form for prevention of atherothromboses for the patients with myocardial infarction, acute coronary syndrome, ischemic stroke, occlusive arterial disease. As a result of biopharmaceutical investigations it was established that combination of excipients – the base (mixture of polyethyleoxydes with molecular weight 1500 and 400 in ratio 9:1) and surface-active substance (twin-80) provides optimal releasing of clopidogrel from the rectal suppository. The aim of this work is scientific substantiation of surface-active substance (twin-80) concentration in rectal dosage form with clopidogrel. Materials and methods . Suppositories were made by the fusiom method using the forms from the Franco-Krespy semi-automatic device. Concentration of surfactant (twin-80) was 0,5%, 1%, 2%, 3% and 5% of drug mass, clopidogrel content was 0,075 g in each suppository. As a parameter of optimization a clopidogrel releasing from suppository compositions was chosen as a first stage of bioavailability study. Clopidogrel releasing from the suppository was studied using the equilibrium dialysis method by Kruvchinsky at 37±0,5 0 С temperature throuth the semipermeable membrane – cellophane film «Kuprofan» in a station with Franz diffusion cells (producer is «Permegear, Inc»., USA). As a dialysis medium taking into account clopidogrel solubility methyl alcohol was chosen. Concentration of clopidogrel released after 30 min was determined by the spectrophotometric method using the spectrofotometer UV – 2600 (producer is«Shimadzu Corp»., Japan). Results . Analysis of variance showed significant influence of surfactant (twin-80) concentration on the clopidogrel releasing from the suppository compositions. Verification of average results of clopidogrel releasing by the Dunkan’s multiple rank test showed that increasing of twin-80 concentration in rectal suppository with clopidogrel more than 2% doesn’t lead to increasing of its releasing from the dosage form. Conclusions . As a result of carried out biopharmaceutical study of clopidogrel suppository it was determined that surfactant (twin-80) concentration has a statistically significant influence on its releasing from the dosage form. It was found out that 2% concentration of twin-80 provides with the optimal level of clopidogrel releasing from the rectal suppository.

Pharmacokinetic interactions of clopidogrel with quercetin, telmisartan, and cyclosporine A in rats and dogs

In this study, we investigated pharmacokinetic drug interactions of clopidogrel with P-gp inhibitors in rats and dogs. Following the oral administration of clopidogrel with or without the P-gp inhibitors, quercetin (250 mg/kg), telmisartan (8 mg/kg), and cyclosporine A (10 mg/kg), in rats and dogs, the plasma concentration-time profiles of clopidogrel carboxylic acid, a surrogate marker for the bioavailability of clopidogrel, were determined. Co-administration of the quercetin, telmisartan and cyclosporine A significantly increased the area under the curve and peak plasma concentration of clopidogrel carboxylic acid in rats. However, in dogs, the plasma concentrations of clopidogrel carboxylic acid were not considerably changed by the coadministration of three different kinds of P-gp inhibitors. These findings suggest potential interaction of clopidogrel with quercetin, telmisartan, and cyclosporine A, although there are differences between animal models. Follow-up clinical study is needed to explore the meaning of this remarkable species differences in the P-gp-mediated interaction.

Determination of Clopidogrel Carboxylic Acid in Human Plasma by LC-MS/MS

Background: Clopidogrel, is a thienopyridine derivative labeled for use to prevent thrombosis after coronary artery stenting. Pharmacokinetics of clopidogrel is studied indirectly by quantification of carboxylic acid which is a major metabolite of Clopidogrel. Objective: The aim of this work is to develop and validate a rapid, simple and sensitive LC/MS/MS assay method for the determination of Clopidogrel carboxylic acid in human plasma using Clopidogrel-D4-carboxylic acid as internal standard. Methods: Analytes was extracted from 200 μl of plasma by a simple liquid-liquid extraction using diethyl ether – n-hexane (80:20, v/v). The chromatographic separations were achieved on a C18 column using Methanol, de-ionized water and formic acid as a mobile phase at flow rate of 0.5 ml/minute. Analysis was monitored by multiple reactions monitoring mode based on m/z transition of 308.10→113 for Clopidogrel carboxylic acid and 312.10→129 for internal standard. Result: The method had a total run time of about 4 minutes. The lower limit of quantification (LLOQ) was 25 ng/ml showing good linearity over the working range of 25 – 3000 ng/ml (r ≥ 0.999). The intra- and inter day accuracies were 90% - 98% and 92.138% - 96.889% respectively (deviation within acceptable range ≤ 10%).Conclusion: It was shown that this method is suitable for pharmacokinetic study following oral administration of Clopidogrel and can be successfully applied to the therapeutic drug monitoring of Clopidogrel in Clopidogrel-treated patients.

P2Y12Receptors in Spinal Microglia Are Required for Neuropathic Pain after Peripheral Nerve Injury

Extracellular nucleotides have been implicated as signaling molecules used by microglia to sense adverse physiological conditions, such as neuronal damage. They act through purinoceptors, especially the G-protein-coupled P2Y receptor P2Y(12)R. Emerging evidence has indicated that activated spinal microglia responding to nerve injury are key cellular intermediaries in the resulting highly debilitating chronic pain state, namely neuropathic pain. However, the role of microglial P2Y(12)Rs in neuropathic pain remains unknown. Here, we show that the level of P2Y(12)R mRNA expression was markedly increased in the spinal cord ipsilateral to the nerve injury and that this expression was highly restricted to ionized binding calcium adapter molecule 1-positive microglia. An increase in the immunofluorescence of P2Y(12)R protein in the ipsilateral spinal cord was also observed after nerve injury, and P2Y(12)R-positive cells were double labeled with the microglial marker OX-42. Blocking spinal P2Y(12)R by the intrathecal administration of its antagonist AR-C69931MX prevented the development of tactile allodynia (pain hypersensitivity to innocuous stimuli), a hallmark of neuropathic pain syndrome. Furthermore, mice lacking P2ry(12) (P2ry(12)(-/-)) displayed impaired tactile allodynia after nerve injury without any change in basal mechanical sensitivity. Moreover, a single intrathecal administration of AR-C69931MX or oral administration of clopidogrel (a P2Y(12)R blocker clinically in use) to nerve-injured rats produced a striking alleviation of existing tactile allodynia. Together, our findings indicate that activation of P2Y(12)Rs in spinal microglia may be a critical event in the pathogenesis of neuropathic pain and suggest that blocking microglial P2Y(12)R might be a viable therapeutic strategy for treating neuropathic pain.

Determination of clopidogrel in human plasma by liquid chromatography/tandem mass spectrometry: application to a clinical pharmacokinetic study

A rapid and sensitive LC/MS/MS assay was developed and validated for the determination of clopidogrel in human plasma. Clopidogrel was extracted by single liquid-liquid extraction with pentane, and chromatographic separations were achieved on a C(18) column. The method was validated to demonstrate the specificity, linearity, recovery, lower limit of quantification (LLOQ), stability, accuracy and precision. The multiple reaction monitoring was based on m/z transition of 322.2 --> 211.9 for clopidogrel and 264.1 --> 125.1 for ticlopidine (internal standard). The total analytical run time was relatively short (3 min), and the LLOQ was 10 pg/mL using 0.5 mL of human plasma. The assay was linear over a concentration range from 10 to 10,000 pg/mL (r > 0.999). The intra- and inter-day accuracies were 101.3-108.8 and 98.4-103.5%, respectively, and the intra- and inter-day assay precisions were 1.9-5.5 and 4.4-8.1%, respectively. The developed assay method was applied to a pharmacokinetic study in human volunteers after oral administration of clopidogrel at a dose of 150 mg.

Effects of combined therapy of clopidogrel and aspirin in preventing thrombus formation on mechanical heart valves in an ex vivo rabbit model

Background: The aim of our study was to investigate the efficacy of the combination of clopidogrel and aspirin in the prevention of thrombus formation on artificial heart valves in an experimental rabbit model as compared to anticoagulation with warfarin. Methods: Studies were performed after oral administration of clopidogrel and aspirin in group I ( n=9) for 5 days, after 5±2 days treatment with warfarin in group II ( n=9) and without medication in group III ( n=9). Leaflets from Sulzer Carbomedics bileaflet valves were placed in a flow chamber. The flow chamber was filled with blood in a continuous circulation between the carotid artery and the jugular vein. Results: In group III, the flow chamber was clotted after a median of 15 min of circulation. Weight analysis before and after 1 h of perfusion showed that the median thrombus weight was 9.1 mg in group I, 14.4 mg in group II and 33.7 mg in group III. Further analysis by electron microscopy showed fewer platelets and erythrocytes on leaflets in group I than on leaflet surfaces in group II. Conclusion: Clopidogrel and aspirin were more effective than warfarin in preventing thrombus formation on artificial heart valve leaflets in our investigation. This rabbit model with a high dosage of clopidogrel and aspirin, and a short-time exposure of the heart valve leaflets to rabbit blood under laminar flow, should be further evaluated with respect to whether it can give information about antithrombotic regimens in patients after mechanical heart valve replacement.

Effect of Various Antiplatelet Agents on Acute Arterial Thrombosis in the Rat

Electrical stimulation of the rat carotid artery causes a deep medial injury and the formation of a platelet-rich thrombus. Occlusive thrombosis at sites of vessel wall injury was significantly reduced after the oral administration of clopidogrel, a potent analogue of ticlopidine, which showed dose-dependent inhibition of the thrombus formation (ED50 = 1.0 +/- 0.2 mg/kg, p.o.). Accumulation of thrombotic material was also considerably reduced after the i.v. administration of SR 27417, a highly potent and selective platelet activating factor receptor antagonist (ED50 = 10 micrograms/kg, i.v.), nafagrel, a thromboxane A2 synthetase inhibitor (ED50 = 1.3 mg/kg, i.v.) and hirudin (ED50 = 140 micrograms/kg, i.v.). A high dose (20 mg/kg, i.v.) of the anti-adhesive tetrapeptide Arg-Gly-Asp-Ser (RGDS) showed only a slight effect on thrombus formation whereas aspirin was ineffective. These results confirm that ADP and thromboxane A2 play key roles in the initiation and progression of arterial thrombus formation and suggest that platelet activating factor may also modulate thrombosis in this experimental model.