Enhanced Antiplatelet Effects of Clopidogrel plus Acetylsalicylic Acid Compared with Acetylsalicylic Acid Alone or Combined with Extended-Release Dipyridamole in Healthy Volunteers

The pharmacological treatment of acute vestibular syndrome

Acute vestibular syndrome (AVS) represents a clinical picture that involves urgent management due to the important procession of symptoms accompanying the event, which can be positively or negatively influenced by therapeutic choices and intervention timing. This forces a differential diagnosis and therapeutic choices to be made in conditions that are not always favorable and often not in the specialist field. In this work, we will examine in detail the pharmacological therapeutic possibilities, correlating them to the differential and, as far as possible, to the etiological diagnosis. In particular, the pharmacological possibilities for the two main conditions we can face will be investigated, namely, vestibular neuritis and posterior circulation stroke.

Platelet Function and Pharmacologic Inhibition

Platelets have traditionally been understood within the context of hemostasis and hemorrhagic disorders. However, with increasing procedures being performed in smaller vessels and with an increasing incidence of atherosclerosis, the often critical role platelets play is more evident. Platelets are no longer viewed as “scaffolding” for the events of the coagulation cascade but rather as important catalysts in hemostasis, thrombosis, and fibrinolysis. Improved understanding of platelet physiology has led to developments of pharmacologic adjuncts resulting in improved patency rates and improved patient outcomes. This review addresses the physiology of platelet function and the impact of new pharmacologic agents in percutaneous intervention.

Bioequivalence and tolerability of two clopidogrel salt preparations, besylate and bisulfate: a randomized, open-label, crossover study in healthy Korean male subjects

BACKGROUND

Clopidogrel, a potent antiplatelet agent, reduces the risk for thrombotic events in patients with atherothrombotic diseases. Clopidogrel is marketed primarily as a bisulfate salt. A different salt preparation of clopidogrel, clopidogrel besylate, has been developed and might provide an additional treatment option for patients.

OBJECTIVE

The aim of this study was to compare the pharmacokinetic, pharmacodynamic, and tolerability profiles of clopidogrel besylate with those of clopidogrel bisulfate to determine bioequivalence for the purposes of marketing approval.

METHODS

A randomized, open-label, 2-period, single- and multiple-dose, comparative crossover study was conducted in healthy Korean male subjects. The subjects received either clopidogrel bisulfate or clopidogrel besylate as a single 300-mg oral loading dose (day 1) followed by a 75-mg/d (once daily) maintenance dose on days 2 to 6. After a 15-day washout period, subjects were administered the alternative salt preparation according to the same protocol. The plasma concentrations of clopidogrel and its primary metabolite (SR26334) were assessed using high-performance liquid chromatography/tandem mass spectrometry after administration of the loading dose. The platelet aggregation response to 10-mumol/L adenosine diphosphate was measured using turbidometric aggregometry during the single- and multiple-dosing periods and at steady state (day 6). Tolerability was monitored using physical examination, including vital sign measurements, and laboratory analysis.

RESULTS

Forty-four subjects were enrolled and completed the study (mean [SD] age, 24.3 [2.7] years; weight, 70.0 [8.2] kg). The mean values for C(max), T(max), and AUC(0-t) with clopidogrel (parent drug) of clopidogrel besylate (5.2 ng/mL, 0.9 hour, and 10.1 ng/mL/h, respectively) were similar to those with clopidogrel bisulfate (5.4 ng/mL, 0.9 hour, and 10.3 ng/mL/h). The mean values for Cmax, AUC(0-t), and AUC(0-infinity) with the SR26334 of clopidogrel besylate (10.9 microg/mL, 38.8 microg/mL/h, and 43.0 microg/mL/h, respectively) were not significantly different from those with the SR26334 of clopidogrel bisulfate (11.9 microg/mL, 40.6 microg/mL/h, and 43.8 microg/mL/h). The mean values for maximal antiplatelet effect (Emax) and area under the time-effect curve (AUEC) with the 2 clopidogrel salt preparations were as follows: clopidogrel besylate, 58.8 h . % and 4299.1 h . % inhibition, respectively; and clopidogrel bisulfate, 61.7 h . % and 4406.9 h . % inhibition; these differences were not statistically significant. The 90% CIs for the ratios of the log-transformed C(max), AUC, E(max), and AUEC values were within the predetermined bioequivalence range of 80% to 125%. Three adverse events (6.8%) were reported during the study and included abdominal discomfort (1 subject [2.3%] in the group that received clopidogrel bisulfate), easy fatigability (1 subject [2.3%] immediately before administration of loading dose of clopidogrel besylate), and thrombocytopenia (1 subject [2.3%] in the group receiving the clopidogrel bisulfate). All adverse events were transient and mild.

CONCLUSIONS

In these healthy Korean male subjects, the differences in the pharmacokinetic and pharmacodynamic properties between the 2 clopidogrel salt preparations did not reach statistical significance and met the regulatory requirements for bioequivalence. Both preparations were well tolerated.

Superior efficacy of clopidogrel plus acetylsalicylic acid compared with extended-release dipyridamole plus acetylsalicylic acid in preventing arterial thrombogenesis in healthy volunteers

INTRODUCTION

Recent ex vivo platelet aggregometry data indicate that clopidogrel 75 mg/day plus acetylsalicylic acid (ASA) 75 mg/day is a more potent antiplatelet regimen than the marketed combination of dipyridamole+ASA. The present study was designed to assess the antithrombotic effect of both dual antiplatelet regimens using a human ex vivo model of arterial thrombosis.

MATERIALS AND METHODS

This was a randomized, double-blind, placebo-controlled, crossover study. During two 10-day treatment periods separated by a 14-day washout period, 23 healthy male volunteers received once-daily clopidogrel 75 mg plus acetylsalicylic acid 75 mg, or twice-daily extended-release dipyridamole 200 mg plus acetylsalicylic acid 25 mg. Assessments were made at baseline and on Day 10 of each period. Arterial thrombus formation was induced ex vivo by exposing a collagen-coated surface in a parallel-plate perfusion chamber to native blood for 3 min (arterial wall shear rate 2600 s(-1)). Total platelet and fibrin deposition was determined by immunoenzymatic methods.

RESULTS

Compared with baseline values, the mean inhibition of total platelet deposition was 63.9+/-5.9% with clopidogrel plus acetylsalicylic acid, compared with 18.4+/-5.6% for extended-release dipyridamole plus acetylsalicylic acid (67% reduction; 95% CI, 49-79%; p<0.0001). Corresponding figures for fibrin deposition were 64.9+/-4.8% and 18.3+/-9.7%, respectively (58% reduction; 95% CI, 45-67%; p<0.0001). Both treatments were well tolerated.

CONCLUSIONS

Clopidogrel plus acetylsalicylic acid showed significantly superior antithrombotic efficacy compared with extended-release dipyridamole plus acetylsalicylic acid in preventing arterial thrombogenesis in humans.