Ticlopidine. An updated review of its pharmacology and therapeutic use in platelet-dependent disorders

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.

Highly productive and scalable approach to synthesize ticlopidine: A potent thienopyridine anti-platelet aggregation drug

Ticlopidine (trade name Ticlid), an acidic thienopyridine derivative, is an effective, well-known and long-acting inhibitor of platelet aggregation. Because of its potent inhibitory activity for treating a variety of diseases, the development of efficient approaches for accessing ticlopidine represents an important endeavour. Therefore, in this research work, we developed a promising novel five-step synthetic approach for synthesizing ticlopidine. This method provides ticlopidine in 60% overall yield from readily available starting material viz. thiophene. In this methodology, all steps afforded excellent yields and are operationally simple and environmentally acceptable. This approach also offers various attractive advantages, for example, it's applicable for large-scale synthesis, has simple work-up procedures and short reaction times, and uses inexpensive and readily available reagents. Furthermore, 4,5,6,7-tetrahydrothieno[3,2-c]pyridine is a key precursor for the synthesis of numerous bioactive compounds such as prasugrel and clopidogrel. This protocol provides 4,5,6,7-tetrahydrothieno[3,2-c]pyridine in 62% overall yield via a 4-step synthetic approach.

The FDA-approved drugs ticlopidine, sertaconazole, and dexlansoprazole can cause morphological changes in C. elegans

Urgent need for treatments limit studies of therapeutic drugs before approval by regulatory agencies. Analyses of drugs after approval can therefore improve our understanding of their mechanism of action and enable better therapies. We screened a library of 1443 Food and Drug Administration (FDA)-approved drugs using a simple assay in the nematode C. elegans and found three compounds that caused morphological changes. While the anticoagulant ticlopidine and the antifungal sertaconazole caused both accumulations that resulted in distinct distortions of pharyngeal anatomy and lethality upon acute exposure, the proton-pump inhibitor dexlansoprazole caused molting defects and required exposure during larval development. Such easily detectable defects in a powerful genetic model system advocate the continued exploration of current medicines using a variety of model organisms to better understand drugs already prescribed to millions of patients.

Ticlopidine Improves Dialysis Clearance of Solutes in Uremic Patients by Reducing Blood Clotting in Dialyser Fibers

Ticlopidine, a platelet aggregation inhibitor was tested, in a double blind comparative cross-over study versus placebo, in 51 dialysed uremic patients who had increased dialyser blood clotting (> 25 fibers clotted / dialyser). At the end of a 7-day treatment period with 250 mg daily, the clearance of urea, creatinine and phosphate was determined at 30 and 210 minutes of dialysis, as well as the number of fibers clotted at the end of dialysis. Ticlopidine improved dialyser clearances for urea, creatinine and phosphate from 165 ± 41 to 182 ± 35 (p < 0.01), 135 ± 37 to 143 ± 35 (p < 0.05), and 120 ± 36 to 130 ± 35 (p < 0.05) ml/min, respectively, at 30 min of HD and a similar effect was seen after 210 min of dialysis. The number of dialyser fibers clotted after dialysis was reduced by ticlopidine therapy from 110 ± 48 to 15 ± 8 (p < 0.01). Ticlopidine reduced the initial dialysis-induced drop in leucocyte count by 20% (p < 0.05); no change in platelet or erythrocyte count was observed. Two out of 51 patients experienced an adverse reaction from ticlopidine (cutaneous haematoma and minor gingival bleeding). We conclude that ticlopidine is an efficient and safe drug for dialysed uremic patients since it can reduce blood clotting and thereby increase dialysis efficiency.

Antiplatelet agents in hemodialysis

Patients affected by cardiovascular disease (CVD) are treated with antiplatelet agents (AA) and/or anticoagulant drugs, which are fundamental in the management of stroke, coronary atherosclerotic disease, peripheral vascular disease and atrial fibrillation. CVD is the most important cause of death in chronic renal failure (CRF). Death rates from myocardial infarction (MI) and from all other cardiac causes exceed those for the general population. Incidence of MI in CRF is triple that in the general population. Moreover, mortality is seven- to eight-fold higher in patients requiring chronic hemodialysis compared to the general population, and approximately 40% of deaths in this population are attributable to coronary artery disease (CAD). For these reasons, AA are widely used in patients affected by CRF. Current data do not support a protective effect of antiplatelet administration in hemodialytic patients as primary prevention of cardiovascular mortality. Different results have been obtained concerning secondary prevention of CVD. The Cooperative Cardiovascular Project demonstrated that dialysis patients treated with aspirin following MI had a 43% lower mortality. Another study reported that the use of aspirin and beta-blockers following MI was associated with lower mortality in CRF patients. However, aspirin plus clopidogrel seems to increase the hemorrhagic risk without a significant reduction in cardiovascular mortality and there are insufficient data to support the use of new AA drugs in hemodialytic patients. In conclusion, since CRF patients are one of the groups at highest risk for atherosclerotic events, it could be reasonable to use aspirin in HD patients. However, the bleeding risk in HD patients needs to be strongly evaluated, especially before starting dual AA treatment.

The Effects of Ergoloid Mesylates and Ginkgo Biloba on the Pharmacokinetics of Ticlopidine

Ticlopidine is sometimes coadministered with ergoloid mesylates or ginkgo biloba in clinical situations. Our objective was to examine the effect of ergoloid mesylates and ginkgo biloba on ticlopidine pharmacokinetics. Ticlopidine, ergoloid mesylates, and ginkgo biloba significantly inhibited the organic anion transporting polypeptide (OATP-B)-mediated uptake of [(3)H]-estrone-3-sulfate in a concentration-dependent manner. When ergoloid mesylates was coadministered with ticlopidine, the ticlopidine area under the plasma drug concentration-time profile (AUC) from 0 to 12 hours was decreased 30% and the peak plasma drug concentration (C(max)) was decreased 29%, compared with ticlopidine administration alone. There were no significant changes in the pharmacokinetic parameters of ticlopidine when it was coadministered with ginkgo biloba. In summary, ergoloid mesylates is a more potent inhibitor of OATP-B than is ginkgo biloba, and it can reduce the oral bioavailability of drugs transported by OATP-B. Ergoloid mesylates markedly decreased the AUC and C(max) of ticlopidine, probably by inhibiting the OATP-B-mediated uptake of ticlopidine during the intestinal absorption phase. The results support a new model of intestinal drug-drug interaction.

Newer agents in antiplatelet therapy: a review

Antiplatelet therapy remains the mainstay in preventing aberrant platelet activation in pathophysiological conditions such as myocardial infarction, ischemia, and stroke. Although there has been significant advancement in antiplatelet therapeutic approaches, aspirin still remains the gold standard treatment in the clinical setting. Limitations in safety, efficacy, and tolerability have precluded many of the antiplatelet inhibitors from use in patients. Unforeseen incidences of increased bleeding risk and recurrent arterial thrombosis observed in patients have hampered the development of superior next generation antiplatelet therapies. The pharmacokinetic and pharmacodynamic profiles have also limited the effectiveness of a number of antiplatelet inhibitors currently in use due to variability in metabolism, time to onset, and reversibility. A focused effort in the development of newer antiplatelet therapies to address some of these shortcomings has resulted in a significant number of potential antiplatelet drugs which target enzymes (phosphodiesterase, cyclooxygenase), receptors (purinergic, prostaglandins, protease-activated receptors, thromboxane), and glycoproteins (αIIbβ3, GPVI, vWF, GPIb) in the platelet. The validation and search for newer antiplatelet therapeutic approaches proven to be superior to aspirin is still ongoing and should yield a better pharmacodynamic profile with fewer untoward side-effects to what is currently in use today.

Thienopyridine derivatives versus aspirin for preventing stroke and other serious vascular events in high vascular risk patients

BACKGROUND

Aspirin is the most widely studied and prescribed antiplatelet agent for preventing serious vascular events, reducing the odds of such events among high vascular risk patients by about a quarter. Thienopyridine derivatives inhibit platelet activation by a different mechanism and so may be more effective.

OBJECTIVES

To determine the effectiveness and safety of thienopyridine derivatives (ticlopidine and clopidogrel) versus aspirin for preventing serious vascular events (stroke, myocardial infarction (MI) or vascular death) in patients at high risk, and specifically in patients with a previous TIA or ischaemic stroke.

SEARCH STRATEGY

We searched the trials registers of the Stroke, Heart and Peripheral Vascular Diseases Cochrane Review Groups (last searched July 2008), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2008), MEDLINE (1966 to August 2008) and EMBASE (1980 to August 2008). We also searched reference lists of relevant papers, and contacted other researchers and the pharmaceutical company Sanofi-BMS (December 2008).

SELECTION CRITERIA

All unconfounded, double blind, randomised trials directly comparing a thienopyridine derivative with aspirin in high vascular risk patients.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. We sought additional data from the principal investigators of the largest trials.

MAIN RESULTS

We included 10 trials involving 26,865 high vascular risk patients. The trials were generally of high quality. Aspirin was compared with ticlopidine in nine trials (7633 patients) and with clopidogrel in one trial (19,185 patients). Compared with aspirin, allocation to a thienopyridine produced a modest, just statistically significant, reduction in the odds of a serious vascular event (11.6% versus 12.5%; odds ratio (OR) 0.92, 95% confidence interval (CI) 0.85 to 0.99), corresponding to the avoidance of 10 (95% CI 0 to 20) serious vascular events per 1000 patients treated for about two years. However, the wide confidence interval includes the possibility of negligible additional benefit. Compared with aspirin, thienopyridines significantly reduced gastrointestinal adverse effects. However, thienopyridines increased the odds of skin rash and diarrhoea, ticlopidine more than clopidogrel. Allocation to ticlopidine, but not clopidogrel, significantly increased the odds of neutropenia. In patients with TIA/ischaemic stroke, the results were similar to those for all patients combined.

AUTHORS' CONCLUSIONS

The thienopyridine derivatives are at least as effective as aspirin in preventing serious vascular events in patients at high risk, and possibly somewhat more so. However, the size of any additional benefit is uncertain and could be negligible. Clopidogrel has a more favourable adverse effects profile than ticlopidine and so is the thienopyridine of choice. It should be used as an alternative to aspirin in patients genuinely intolerant of or allergic to aspirin.

Clinical pharmacology of antithrombotic drugs in coronary artery disease

Coronary heart disease is the leading cause of death in the Western world. Antithrombotic therapy is the cornerstone of its successful treatment. Clinical trials have demonstrated that antithrombotic therapy reduces the risk for recurrent myocardial infarction and cardiovascular death. Antiplatelet drugs and anticoagulants interfere with haemostasis and thus bleeding is a major risk factor of these drugs. The benefit of antithrombotic therapy must therefore be carefully balanced with the risk of bleeding and other potential adverse reactions of these drugs. However, to date there is no firm evidence that dosage adaptation of aspirin or clopidogrel according to platelet aggregation testing translates directly into any clinical benefit. Resistance to antithrombotic drugs is a serious problem because these patients are at a higher risk of myocardial infarction, stroke and cardiovascular death. It has most recently been demonstrated that resistance to clopidogrel is at least in part caused by polymorphism of CYP2C19. Clinical trials have also demonstrated that optimal benefit in different settings depends unequivocally on the meticulous choice of the various drugs. Thus, profound knowledge of the clinical pharmacological profiles of the different antithrombotic drugs is indispensable for successful treatment.

Secondary stroke prevention: inside the vessels and beyond

Cerebral ischaemic stroke is frequently a relapsing, if not chronic, disease. Its incidence is age-dependent, and with the ageing of society the need for effective therapies increases. This review considers current and alternative hypotheses underlying secondary prevention of stroke. Currently, secondary stroke prevention is widely practiced with aspirin (acetylsalicylic acid), a drug that has been in use for more than 100 years. Newer drugs such as ticlopidine and clopidogrel have subsequently been developed, but their efficacy barely surpasses that of aspirin. Other drugs used in secondary stroke prevention include HMG-CoA reductase inhibitors and antihypertensive agents. The endovascular paradigm has shaped the thinking of secondary stroke prevention, and aspirin, ticlopidine and clopidogrel are known as 'platelet inhibitors'; however, their pharmacological and clinical effects are not fully explained within the platelet paradigm. Moreover, in recent years, reduction of stroke incidence has also been observed with HMG-CoA reductase inhibitors, regardless of their lipid-lowering effects. Hence, current understanding needs to be supplemented by considering mechanisms beyond platelet inhibition. Evidence has shown that aspirin, ticlopidine and clopidogrel share neuroprotective properties not explained by the platelet paradigm and that are reminiscent of a preconditioning effect. This neuroprotective mechanism is also shared with HMG-CoA reductase inhibitors.

Comparison of sarpogrelate and ticlopidine in bare metal coronary stent implantation

BACKGROUND

The efficacy and safety of sarpogrelate, a selective 5-hydroxytryptamine receptor subtype 2A antagonist, have not yet been established in bare metal coronary stenting. Accordingly, we sought to clarify whether treatment with sarpogrelate is clinically useful in bare metal coronary stenting.

METHODS

A total of 450 patients who underwent successfully planned or unplanned bare metal coronary stenting were randomly divided into the following 2 groups: the sarpogrelate (300 mg/day) plus aspirin (100 mg/day) group (group S, n=225) and the ticlopidine (200 mg/day) plus aspirin (100 mg/day) group (group T, n=225). Either sarpogrelate or ticlopidine was administered for at least 4 weeks after the procedure. Follow-up coronary arteriography was performed at 6 months after the procedure. The primary endpoints were the incidence of adverse drug reactions requiring a withdrawal of treatment and the rate of binary restenosis. The secondary endpoint was the incidence of stent thrombosis.

RESULTS

The incidence of adverse drug reactions requiring a withdrawal of treatment was significantly lower in group S than in group T (0.44% vs 8%, p=0.002). The rate of binary restenosis did not differ significantly between groups S and T (16.9% vs 18.2%). In addition, the incidence of subacute stent thrombosis did not differ between groups S and T (0.44% vs 0.44%).

CONCLUSIONS

The incidence of adverse drug reactions requiring a withdrawal of treatment was significantly lower with sarpogrelate use than with ticlopidine use. The rate of binary restenosis and the incidence of subacute stent thrombosis did not differ between both drug groups.

Acquired platelet dysfunction

Acquired platelet dysfunction is encountered frequently in clinical practice. The usual clinical presentation is that of mucosal bleeding, epistaxis, or superficial epidermal bleeds. Often, the dysfunctional platelets are related to a medication or a systemic disorder. Normally, when platelets are exposed to damaged endothelium, they adhere to the exposed basement membrane collagen and change their shape from smooth disks to spheres with pseudopodia. Then, they secrete the contents of their granules, a process referred to as the release reaction. Additional platelets form aggregates on those platelets that have adhered to the vessel wall. As a result, the primary hemostatic plug is formed, and bleeding is arrested. This article reviews the various forms of acquired platelet dysfunction that result in decreased platelet aggregation, adhesion, or secretion.

Repeat oral dosing of prasugrel, a novel P2Y12 receptor inhibitor, results in cumulative and potent antiplatelet and antithrombotic activity in several animal species

Antiplatelet and antithrombotic activity of multiple oral dosing of prasugrel were evaluated in several animal species. Prasugrel's active metabolite concentration-relatedly inhibited in vitro ADP-induced aggregation of rat, rabbit, dog, monkey and human platelets. Oral administration of prasugrel to dogs (0.03-0.3 mg/kg/day) and monkeys (0.1 and 0.3 mg/kg/day) once a day for 14 days resulted in potent, dose-related and cumulative inhibition of ADP-induced platelet aggregation. The inhibitory effects reached a plateau on days 3 to 5 and thereafter were maintained during dosing. Inhibition decreased gradually after cessation of dosing with near full recovery by 7 days after last dose. Antiplatelet and antithrombotic activity of prasugrel and clopidogrel were further examined in rats. Multiple oral dosing of prasugrel (0.3-3 mg/kg/day) to rats resulted in more potent inhibition of platelet aggregation compared to clopidogrel (3-30 mg/kg/day) and ticlopidine (30-300 mg/kg/day). Separate experiments confirmed that platelet inhibition was associated with inhibition of [(3)H]-2-methylthio-ADP binding to rat platelets. In a rat model of electrically-induced arterial thrombosis, prasugrel (0.1-1 mg/kg/day, p.o.) significantly prolonged the time to arterial occlusion and increased the duration of arterial patency. The inhibition of platelet aggregation of prasugrel was about 10 and 300 times more potent than clopidogrel and ticlopidine, respectively. Overall these results show that in several species multiple oral administration of prasugrel results in more potent inhibition of platelet aggregation and thrombus formation than clopidogrel and ticlopidine, and that these effects are mediated by inhibition of platelet ADP receptors.

Newer Pharmacotherapy in Patients Undergoing Percutaneous Coronary Interventions: A Guide for Pharmacists and Other Health Care Professionals

Significant advances in pharmacotherapy for patients undergoing percutaneous coronary intervention (PCI) have occurred during the past decade, including the introduction and approval of new antithrombin and antiplatelet therapies, as well as modifications in dosing, administration, and/or duration of older pharmacotherapy regimens. Also, off-label (i.e., not approved by the United States Food and Drug Administration) use of certain agents has become common. Given the novel nature of these agents and the nuances of therapy, the pharmacist and other health care professionals should play an integral role in collaboration with interventional cardiologists in development of hospital protocols, determination of appropriate agent selection, assessment of patient renal function and hematologic status, dosing, and monitoring for adverse effects. In this guide, the newer antiplatelet and antithrombin drugs that may be used during PCI are reviewed, and recommendations regarding the proper administration of these agents are provided.

Oral antiplatelet therapy and percutaneous coronary intervention

The benefit of oral antiplatelet therapy following percutaneous coronary intervention (PCI) with intracoronary stent implantation is well established. Combined aspirin with clopidogrel or ticlopidine therapy is superior to aspirin alone in reducing thrombotic events after stent placement. Clopidogrel is the drug of choice, given that its efficacy is comparable to ticlopidine and it has a superior safety profile. Despite dual antiplatelet therapy, patients remain at risk of recurrent vascular events. Optimal timing, duration and dosage of antiplatelet therapy remain controversial. Recent evidence suggests additional benefit with clopidogrel pretreatment, high clopidogrel loading dose and long-term dual antiplatelet therapy post-PCI in high-risk patients.

Bisphosphonates as anti-inflammatory agents in ankylosing spondylitis and spondylarthropathies

NSAIDs remain the cornerstone of the treatment of ankylosing spondylitis (AS) and spondylarthropathies (SpA), and have been successfully used for a long time in these diseases. However, some patients remain refractory or intolerant to NSAIDs and new effective treatments have recently emerged, namely TNF-alpha-blocker agents. Other therapeutic options targeting the bone, such as bisphosphonates, have also been tried in refractory AS or SpA patients. The anti-inflammatory properties of bisphosphonates give the rationale for the use of these compounds in AS and SpA, and include the inhibition of antigen presenting cells, the modulation of pro-inflammatory cytokine generation, and also a decreased bone mass in AS. Open trials using pamidronate gave favourable results, and one controlled study comparing the efficacy of pamidronate 10 versus 60mg showed that the 60mg dose was effective in AS. Further studies are required to confirm these preliminary data and to better determine the optimal regimen (dosage and rhythm) of administration.

Antiplatelet and Antithrombin Therapy for Early Management of Acute Coronary Syndromes

Acute coronary syndromes (ACS) are defined as either unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), or ST-segment elevation myocardial infarction (STEMI). Their management is continuously evolving in terms of pharmacologic therapy. The usual cause of ACS is the disruption of an atherosclerotic plaque leading to formation of a thrombus within a coronary artery. Initial antiplatelet and antithrombin therapy for patients with ST-segment elevation (STE) ACS includes aspirin and unfractionated heparin (UFH). Patients presenting to the hospital early may undergo percutaneous intervention (PCI) with administration of additional medications such as clopidogrel and abciximab or may receive a fibrinolytic agent. Patients with non-ST-segment elevation (NSTE) ACS receive aspirin, clopidogrel, either a low-molecular-weight heparin or UFH, and, in selected patients, a glycoprotein (GP) IIb/IIIa receptor blocker. All of these agents have shown benefit when administered to patients with ACS, but results vary depending on the type of syndrome, timing of administration, and patient’s overall risk. Their mechanism of action, role in ACS, clinical practice recommendations, adverse effects, and monitoring are reviewed. Some inherent limitations to agents such as aspirin and UFH require the need for newer treatment approaches. Therefore, newer classes of drugs such as the direct thrombin inhibitor bivalirudin and the selective factor Xa inhibitor fondaparinux are being explored as alternatives to heparins for ACS management.

Evaluation of antiplatelet effects of ticlopidine in cats

OBJECTIVE

To determine whether ticlopidine exerts an antiplatelet effect, estimate the pharmacodynamics of ticlopidine, and evaluate any acute adverse effects associated with administration of ticlopidine in cats.

ANIMALS

8 domestic purpose-bred sexually intact male cats.

PROCEDURE

Ticlopidine was administered orally (50 mg, q 24 h; 100 mg, q 24 h; 200 mg, q 24 h; and 250 mg, q 12 h). Each treatment period consisted of 10 days of drug administration. Platelet aggregation studies with adenosine diphosphate (ADP) and collagen and evaluation of oral mucosal bleeding times (OMBTs) were performed on days 3, 7, and 10 during each drug administration. Serotonin was measured to evaluate secretion at baseline and on day 10 for cats that received the 250-mg dosage.

RESULTS

A significant reduction in platelet aggregation was detected in response to ADP on days 7 and 10 at 100 mg, on day 3 at 200 mg, and on days 3, 7, and 10 at 250 mg. A significant increase in the OMBT and decrease in serotonin release on day 10 at 250 mg was also detected; however, the cats had anorexia and vomiting at the 250-mg dosage.

CONCLUSIONS AND CLINICAL RELEVANCE

Although there was a consistent antiplatelet effect at the 250-mg dosage, there was dose-dependent anorexia and vomiting that we conclude precludes the clinical usefulness of this drug in cats.

Platelet ADP receptor antagonists: ticlopidine and clopidogrel

The central role of platelets in the pathophysiology of arterial vascular disease has focused attention on the development of effective platelet inhibitor modalities to mitigate the clinical consequences of atherothrombotic disease. Aspirin has been the gold standard of therapy and is effective in cerebral, coronary and peripheral arterial disease with a 25% reduction in myocardial infarction, stroke and vascular death. The platelet ADP receptor antagonists were developed to further improve the clinical results of therapy. Ticlopidine provides an additional 10% relative risk reduction over aspirin alone in stroke prevention and coronary stent placement. However, ticlopidine is accompanied by occasional life-threatening adverse hematological events. The action of clopidogrel is similar to that of ticlopidine, and it is comparably effective. However, the side-effect profile of clopidogrel is much more favorable.

Timing of anti-platelet effect after oral aspirin administration in patients with sympathetic excitement

Aspirin is used in percutaneous coronary interventions (PCI) for acute myocardial infarction (AMI) to prevent thrombosis. It is reported that the aspirin concentration in blood reaches its peak approximately 20 min after oral administration in healthy volunteers, but the absorption and bioavailability of aspirin in AMI may be quite different. In the present study patients undergoing coronary angiogram for the first time were enrolled as a model of sympathetic excitement and the timing of the antiplatelet effect after oral aspirin administration was investigated. Aspirin (162 mg) was administered to the patients in a catheter laboratory. Platelet count, aspirin concentration, and platelet aggregation were measured at scheduled timepoints before and up to 120 min. Ticlopidine was administered in the same procedure, and platelet count and platelet aggregation were evaluated at 0 and 120 min. There was no significant change in the platelet count. Aspirin concentration in blood had not reached its peak by 120 min. Platelet aggregation induced by collagen or ADP began to be inhibited 45 min after aspirin administration. No significant inhibition of platelet aggregation was observed up to 120 min following ticlopidine administration. During sympathetic excitement, aspirin absorption and its antiplatelet effect were significantly delayed in these patients. Ticlopidine did not show any antiplatelet effect by 120 min. For PCI performed in a patient with a high level of sympathetic excitement, aspirin should be administered at least 45 min before the first balloon dilatation.

Assessment of the effects of D-003, a new antiplatelet and lipid-lowering compound, in healthy volunteers. A phase I clinical study

OBJECTIVE

To investigate the effects of D-003 on the bleeding time (BT) and lipid profile of healthy human volunteers.

METHODS

This single-blind, randomised, placebo-controlled, parallel-group study was conducted in healthy volunteers. Step 1 investigated the effects of single doses of D-003 5, 25 or 50 mg on BT in comparison with placebo. Step 2 investigated the effects of 30 days of D-003 5, 25 or 50 mg/day compared with placebo on lipid profile with an interim assessment at 14 days. BT, lipid profile, physical and haematological safety indicators were measured and adverse events (AEs) recorded. Both steps were followed by a 14- or 30-day washout period.

RESULTS

Step 1: D-003 25 and 50 mg significantly increased mean BT 2 hours after administration compared with baseline, but a significant difference versus placebo occurred only with the 50 mg dose. Individual values from participants taking this dose, however, remained within normal limits. This effect was reversible. BT values obtained 2 hours after drug administration showed a moderate dose-dependent relationship. No drug-related changes in safety indicators were found with D-003. Step 2: After 7 days on D-003 50 mg/day, BT was significantly increased compared with baseline and placebo up to the end of the active treatment period. However, all individual values for participants taking this dosage remained within the normal range. This effect was reversible by the end of the washout period. After 30 days, D-003 (5, 25 and 50 mg/day) significantly reduced serum TC (by 13.3 to 17.4%) and LDL-C (by 11.6 to 22.6%) levels, and raised HDL-C levels (by 14.6 to 29.7%), but did not affect triglyceride levels. The significant increase in HDL-C was observed after 14 days on treatment. The effects on the lipid profile were reversible by the end of the 30-day washout period, although after 14 days of washout the effects on HDL-C and LDL-C still remained significant, revealing a certain persistence of effect. Eight participants (four receiving placebo and four receiving D-003 5, 25 or 50 mg/day) reported a total of nine AEs, none of which were drug-related. Of these patients, only two treated with D-003 25 and 50 mg/day discontinued treatment.

CONCLUSIONS

D-003 in single or repeated doses (50 mg) induced significant and reversible increases in BT. In addition, repeated doses (5, 25 and 50 mg/day) significantly and reversibly lowered serum LDL-C and TC levels and significantly raised serum HDL-C levels. These effects were reversible by 30 days after the end of treatment.

Elective placement of covered stents in native coronary arteries

PURPOSE

To study the feasibility of placing a polytetrafluoroethylene (PTFE)-covered stent graft into native coronary arteries and assess the complications and the restenosis rate.

MATERIAL AND METHODS

Fifty consecutive patients with stable angina pectoris were included and the stent graft was placed into native coronary arteries. Clinical and angiographic follow-up were performed after 6 months.

RESULTS

The stent grafts were successfully placed in all patients. The mean reference diameter was 3.3 +/- 0.6 mm. During follow-up the stent grafts occluded in patients after 1, 2 and 2.5 months and one more was occluded at 6 months. Three patients experienced myocardial infarction, 2 Q wave and one non-Q wave. After 6 months 42 (84%) patients had angina NYHA class 0 or 1. Target vessel revascularization was done in 11 cases for restenosis in the graft (n = 4), outside the graft (n = 3) and both (n = 4), giving a restenosis rate of 24%. The total major adverse coronary events at 6 months was 24%.

CONCLUSION

The stent graft was deployed with a high success rate. The restenosis rate was not higher than expected for bare stents. However, this study showed that subacute occlusion may occur more frequently and we therefore recommend that ticlopidine or clopidogrel treatment should be prolonged to at least 3 months.

The prevention of minor myocardial injury with ticlopidine pretreatment in patients undergoing elective coronary stenting

The aim of the study was to determine whether ticlopidine treatment prior the coronary stenting would be associated with lower rates of procedure-related minor myocardial injury (MMI) in patients undergoing elective coronary stenting. In this retrospective, nonrandomized, uncontrolled study, a total of 153 consecutive patients with a mean age of 63.4+/-8.9 years were divided into two groups based on the duration of ticlopidine treatment: group I (n=81), ticlopidine >/=3 days before the procedure, group II (n=72), on the same day as stent placement. Cardiac troponin T (cTnT) was measured immediately before and 12 h after the procedures. All patients were followed-up during the hospital stay with respect to MMI and major clinical events (MCE). The increase frequency and the amount of cTnT level in group I was found to be significantly lower compared with group II (4 vs. 13; P<0.01, and 0.35+/-0.06 vs. 0.52+/-0.11 ng/ml; P<0.01, respectively). In general, patients with elevated cTnT levels are more likely to have C type lesion and multivessel procedure than those of normal cTnT level (41 vs.10%; P<0.002 and 47 vs. 17%; P<0.009, respectively). Though there was a trend toward increased MCE rates in group II than that of group I, this did not reached statistical significance (3 vs.1; P=NS). The present study shows that an anti-platelet treatment with ticlopidine prior the coronary stenting of adequate duration to allow for the development of maximal inhibition is associated with a markedly decreased incidence of procedure-related MMI. Therefore, ticlopidine pretreatment may be a cost alternative for the prevention of platelet-rich microembolism in patients undergoing elective coronary stenting.

Atherosclerosis and cancer: common pathways on the vascular endothelium

This article reviews experimental and clinical data on atherosclerosis and cancer showing common pathogenic mechanisms. It is suggested that common pathways follow dysfunction of the vascular endothelium. The activation of the haemostatic system and the overexpression of cytokines and adhesion molecules by the endothelial cells represent important features of this dysfunction. These mechanisms can be responsible for progression of both diseases and explain the higher incidence of thromboembolic events in cancer patients, the occurrence of similar laboratory findings and the effect of many drugs on the course of the two diseases. Our article confirms that atherosclerosis and cancer share common mechanisms, and we hope it will stimulate further clinical trials on the use of drugs active on the haemostatic system in cancer patients.

Emergency coronary artery bypass surgery in the era of glycoprotein IIb/IIIa receptor antagonist use

The use of intravenous glycoprotein (GP) IIb/IIIa platelet receptor antagonists in the management of patients with acute coronary syndrome or those undergoing percutaneous coronary intervention (PCI) has become increasingly common in recent years. There are three GP IIb/IIIa receptor antagonists currently available for clinical use. Patients on GP IIb/IIIa receptor antagonists who require emergency surgical revascularization may be at increased risk for excessive peri- and postoperative bleeding. The duration of action of eptifibatide and tirofiban are short because they bind reversibly to the GP IIb/IIIa receptor and have a short half-life. Therefore, within a relatively short time after discontinuation of these agents, surgery can be performed with little or no increased risk of bleeding and without the need for additional hemostatic measures. Abciximab has a short plasma half-life but a long duration of action due to its high-affinity binding of GP IIb/IIIa receptors. Early retrospective studies demonstrated a higher incidence of major bleeding and requirement for blood transfusion, especially in those undergoing surgery within 12 hours of the discontinuation of abciximab. However, platelet transfusion has been shown to successfully reduce the incidence of these complications. The current evidence therefore indicates that, with appropriate measures, urgent surgical revascularization can be safely performed in patients who have received a GP IIb/IIIa receptor antagonist with little added risk. The benefits of these agents in the treatment of patients with an acute coronary syndrome or undergoing PCI are not obviated by the need for emergency bypass surgery.

Ticlopidine-induced aplastic anemia: two new case reports, review, and meta-analysis of 55 additional cases

Ticlopidine-induced aplastic anemia (TIAA) is considered very uncommon. We present two new cases, and we review 55 additional cases from the literature. The first case concerns a 70-year-old man who developed severe aplastic anemia 7 weeks after treatment with 500 mg of ticlopidine daily. The patient sustained a severe septic episode, was treated with antibiotics and GM-CSF, and recovered the 14(th) day after ticlopidine withdrawal. The second was an 82-year-old man receiving ticlopidine for 2 years when, during a febrile episode, he was found neutropenic with marrow aplasia. Ticlopidine withdrawal and treatment with antibiotics, transfusions, and G-CSF helped him to recover. When the data of the 57 patients are evaluated, a reversible direct cytotoxic effect of ticlopidine on the pluripotent/bipotent hematopoietic progenitor stem cell is proposed. It is estimated that the real incidence if TIAA is higher, and many cases, initially presented as agranulocytosis +/- thrombocytopenia, might be true aplastic anemias, not proven by marrow aspiration or trephine biopsy. There is no effective monitoring to prevent this side effect. Recombinant growth factors appear not to help in shortening the neutropenic period.

The role of adenosine 5'-diphosphate receptor blockade in patients with cardiovascular disease

Aspirin, which has been the mainstay of antiplatelet agent for many decades, affects a single pathway in the platelet activation process and provides incomplete protection against cardiovascular events. Aspirin also may blunt the hemodynamic effect of angiotensin-converting enzyme inhibitors. Dipyridamole may provide some additional benefit, but there is little evidence to suggest its superiority alone or in combination with aspirin compared to standard doses of aspirin. Oral platelet glycoprotein IIb/IIIa inhibitors, although initially promising, have had disappointing results in recent clinical studies. A new class of medications, the thienopyridines, blocks the activity of platelet adenosine 5'-diphosphate (ADP) receptors, thereby reducing platelet activation. This review discusses the pharmacology, clinical studies, and potential uses of these agents, which include ticlopidine and clopidogrel. ADP inhibitors, by blocking an alternate pathway of platelet activation, are slightly more effective than aspirin in reducing cardiovascular events.

Incidence of thrombotic occlusion and major adverse cardiac events between two and four weeks after coronary stent placement: analysis of 5,678 patients with a four-week ticlopidine regimen

OBJECTIVES

We attempted to make a comprehensive assessment of the risk of stent failure (death, myocardial infarction or angiographically documented occlusion), differentiating early (first and second weeks) and late (third and fourth weeks) events.

BACKGROUND

The risk of stent failure decreases rapidly within the first week. It has been suggested that the risk rate for late events is close to 0% and that the thienopyridine regimen (ticlopidine or clopidogrel) could be safely reduced from four to two weeks, minimizing the risk of hematological complications.

METHODS

We analyzed 5,678 patients with successful coronary stent placement and a four-week ticlopidine regimen.

RESULTS

The rate of stent failure was 2.5% at four weeks, with 112 early (2.0%) and 30 late events (0.5%). Multivariate analysis identified different risk factors for early versus late events. While variables on stenosis severity and procedural results that can be influenced by the operator were identified as independent risk factors for early events (percent stenosis before and after the procedure, residual dissection, length of stented segment), more clinical variables were associated with late events (age, reduced left ventricular function, systemic hypertension as a protective factor). The late-event rate was <0.1% in the absence of these factors, but it was 2.5% with all three risk factors present.

CONCLUSIONS

The risk of late stent failure is low with a four-week ticlopidine regimen. However, high-risk subgroups have a risk of 2.5%. As this rate is presumably higher if thienopyridines are discontinued after two weeks, these data suggest that a risk stratification to a two- or four-week regimen is preferable to a general reduction.

Clinical use of new antithrombotic therapies for medical management of acute coronary syndromes

Prevention and management of acute coronary syndromes (ACS) are focal points of interest among health care providers. Acute coronary syndromes is an all-encompassing term that refers to unstable angina, non-Q wave myocardial infarction, and Q wave myocardial infarction. These syndromes are usually the result of atherosclerotic plaque rupture leading to thrombus formation in a coronary artery. Heparin and aspirin are traditional antithrombotic treatments. They typically are administered with antiischemic therapies and often with fibrinolytic agents for patients with ST segment elevation associated with acute myocardial infarction. Although aspirin and heparin are important, they have significant limitations that have prompted development of newer antithrombotic approaches. Adenosine diphosphate inhibitors have been evaluated as either alternatives or adjunctive treatment to aspirin. Glycoprotein IIb-IIIa receptor inhibitors, low-molecular-weight heparins, and direct thrombin inhibitors have been studied as concurrent therapy with, or as alternatives to, heparin.

Antiplatelet and anticoagulant therapy in elective percutaneous coronary intervention

Thrombosis plays a major role in acute vessel closure both after coronary balloon angioplasty and after stenting. This review will address the role of antiplatelet and anticoagulant therapy in preventing early thrombotic complications after percutaneous coronary intervention. The focus will be on agents that are routinely available and commonly used.

Clopidogrel for prevention of major cardiac events after coronary stent implantation: 30-day and 6-month results in patients with smaller stents

OBJECTIVES

We developed this study to assess the procedural outcome, complications, and clinical follow-up in patients treated with different antiplatelet regimens after intracoronary stent implantation with small stents. Three hundred sixty-one consecutive patients, in whom at least one 3.0-mm intracoronary stent was implanted, were studied.

METHODS

The study was a prospective, observational registry of unselected consecutive patients treated in our institution. Patients who underwent stent implantation between December 1997 and July 1998 were treated with aspirin and ticlopidine; those who received stents between August 1998 and February 1999 were treated with aspirin and clopidogrel.

RESULTS

In the group treated with ticlopidine, there were 190 patients who had 253 lesions treated with 274 stents. Mean age was 59.1 years, 72% were male, 31% had unstable angina, 64% had 1 stent, 36% had >1 stent, and 23% had multivessel intervention. In the group treated with clopidogrel, there were 171 patients who had 226 lesions treated with 245 stents. Mean age was 60.4 years, 79% were male, 26% had unstable angina, 70% had 1 stent, 30% had >1 stent, and 26% had multivessel intervention. Complications at 30 days in the ticlopidine group were death in 1 (0.5%), stent occlusion in 3 (1. 6%; all reopened with repeat angioplasty), non-Q-wave myocardial infarction in 2 (1%), and urgent revascularization in 4 (2%). Complications at 30 days in the clopidogrel group were noncardiac death in 1 (1.2%), cardiac death in 1 (1.2%), stent occlusion in 0, non-Q-wave myocardial infarction in 3 (1.8%), and urgent revascularization in 0. Follow-up was available in 100% of patients in both groups (mean 253 +/- 75 days in the ticlopidine group, 198 +/- 53 days in the clopidogrel group). Complications at >30 days in the ticlopidine group were death in 1 and clinical restenosis in 11 (5.8%); 1 additional patient had an admission with unstable angina to the local hospital. Hence, recurrent angina as a consequence of target lesion restenosis occurred in 5.8%. Complications at >30 days in the clopidogrel group were death in 0 and clinical restenosis in 8 (4.7%); 2 additional patients were admitted with unstable angina to the local hospital, and 1 patient had a myocardial infarction 164 days after stent implantation. Hence, recurrent angina as a consequence of target lesion restenosis occurred in 4.7%. There were no significant differences in complications between the 2 groups.

CONCLUSIONS

Our observations suggest that clopidogrel can be used instead of ticlopidine in patients treated with stents with a diameter of </=3.0 mm, without any increase in major adverse cardiac events, both within the first 30 days and at medium-term follow-up. Clopidogrel has significant cost advantages over ticlopidine, and carries a superior side-effect profile. We suggest that, in combination with aspirin, clopidogrel should replace ticlopidine as standard antiplatelet therapy after intracoronary stent implantation.

Antithrombotic therapy in the cardiac catheterization laboratory: focus on antiplatelet agents

Pharmacologic advances in the use of antithrombotic agents have paralleled the technologic innovations used in patients undergoing coronary interventions. The recognition of the central role of platelets in the development of complications related to coronary interventions led to the investigation and subsequent routine use of several antiplatelet agents as adjuvants to coronary intervention. Thus, the oral agents aspirin and either ticlopidine or clopidogrel are routinely administered after coronary stenting. Intravenous glycoprotein (GP) IIb/IIIa antagonists have been extensively studied and reduce adverse cardiac events in patients undergoing coronary interventions, especially those receiving intracoronary stents. Despite the growing use of GP IIb/IIIa antagonists, much information remains unknown as to the proper dosing and the effects these agents have on other elements of the hemostatic and vascular systems.

Heparin-coated Wiktor stents in human coronary arteries (MENTOR trial). MENTOR Trial Investigators

The purpose of this study was to determine the feasibility, safety, and efficacy of elective stenting with heparin-coated Wiktor stents in patients with coronary artery disease. In experimental studies, heparin coating has been shown to prevent subacute thrombosis and restenosis. Recently, a new method of heparin coating was developed, resulting in a more stable and predictable heparin layer on stent devices. This trial constitutes the first in-human use of this coating procedure, applied on the well-known Wiktor stent device. Heparin-coated Wiktor stent implantation was performed in 132 consecutive patients (132 lesions) in a multicenter international trial from September 1996 to February 1997. Forty-three percent of patients had unstable angina, 33% had previous myocardial infarction, and 10% had diabetes mellitus. Patients were followed for 12 months for occurrence of major adverse cardiovascular events, and 96% of the eligible patients underwent quantitative angiographic control at 6 months. Stent deployment was successful in 95.5% of lesions. Minimal lumen diameter increased by 1.67 +/- 0.48 mm (from 1.02 +/- 0.38 mm before to 2.69 +/- 0.37 mm after the stent implantation). Mean percent diameter stenosis decreased from 67.4 +/- 11.3% before to 18.9 +/- 7.7% after the intervention. A successful intervention (<50% diameter stenosis and no major adverse cardiac events within 30 days) occurred in 97% of the patients. The subacute thrombosis rate was 0.8%, which compares favorably with historical controls of this stent, and a low incidence of postprocedural increase in creatine kinase-MB was noted. At 6 months, event-free survival was 85% and angiographic restenosis rate was 22% with late loss of 0.78 +/- 0.69 mm and a loss index of 0.48 +/- 0.44. Heparin-coated Wiktor stents appeared to be an efficacious device to treat Benestent-like lesions, yielding angiographic and clinical results comparable to a heparin-coated Palmaz-Schatz stent. Despite its use in more complex lesions, the incidence of subacute thrombosis appeared to be lower than historical controls with a similar noncoated stent.

Stent thrombosis: historical perspectives and current trends

Coronary stents are now implanted in more than 70% of percutaneous coronary revascularization procedures. Early enthusiasm for improved acute angiographic results and limited restenosis was dampened initially by a high rate of stent thrombosis and later by the increased bleeding complications of aggressive and complex anticoagulation protocols designed to lower the stent thrombosis risk. More recently, routine high-pressure deployment strategies and anti-platelet drug regimens have lowered the incidence of stent thrombosis to approximately 1% without an increased bleeding risk. The timing of stent thrombosis has also changed from a median of 4-5 days to a median of 1 day after the stent procedure. Risk factors in earlier studies included stenting for threatened or abrupt closure, smaller vessels, longer lesions, and possibly left anterior descending artery lesion location. Modern studies have shown a slightly increased risk for multiple stent use, residual dissection, and smaller final lumen. Optimal therapy for stent thrombosis includes emergent revascularization and anti-thrombotic treatment, although the clinical consequences remain dire despite successful reperfusion. The use of platelet glycoprotein IIb/IIIa inhibitors, especially in high-risk situations may further reduce the incidence of stent thrombosis.

Pharmacological management of intermittent claudication: a meta-analysis of randomised trials

Intermittent claudication, a symptom of atherosclerosis in the large vessels of the lower limbs, greatly affects patient mobility and quality of life. Medical therapy for a moderate form of this condition includes vasodilators, antiplatelet agents and alternative treatments such as ginkgo biloba.A meta-analysis of results from 52 trials (including 5088 patients) was conducted for all current medical therapies for intermittent claudication. After 24 weeks, some of the medical therapies were found to be more effective than placebo for the primary end-points of either pain-free walking distance or maximum walking distance. Vasodilators presented the best results in walking distance. Pentoxifylline offered better results than naftidrofuryl, although the treatment benefit, measured in additional metres walked with treatment than without, was modest. Antiplatelets, ginkgo biloba and levocarnitine were slightly more effective than placebo, although the treatment benefit was of limited clinical importance. On average, patients walked 60m further with therapy than without, and only about half of that added distance was pain-free. Very little consistent information was available for other clinical end-points, such as overall mortality and adverse effects. These data suggest that some of the medical therapy, pentoxifylline in particular, can only modestly increase functional status in patients with moderate intermittent claudication. There is a need for uniformity in research design and reporting of trials. A future trial comparing medical therapy with physical therapy is indicated.

The in vivo pharmacological profile of CS-747, a novel antiplatelet agent with platelet ADP receptor antagonist properties

1. CS-747 is a novel antiplatelet agent that generates an active metabolite, R-99224, in vivo. CS-747 itself was totally inactive in vitro. This study examined in vivo pharmacological profiles of CS-747 after single oral administration to rats. 2. Orally administered CS-747 (0.3 - 10 mg kg(-1)) partially but significantly decreased [(3)H]-2-methylthio-ADP binding to rat platelets. CS-747 (3 mg kg(-1), p.o.) treatment neutralized ADP-induced decreases of cyclic AMP concentrations induced by prostaglandin E(1), suggesting that metabolites of CS-747 interfere with G(i)-linked P2T receptor. 3. CS-747 (0.3 and 3 mg kg(-1), p.o.) markedly inhibited ex vivo washed platelet aggregation in response to ADP but not to thrombin. CS-747 also exhibited a marked inhibition of ADP-induced ex vivo platelet aggregation in PRP with a rapid onset (<0.5 h) and long duration (>3 days) of action (ED(50) at 4 h=1.2 mg kg(-1)). 4. R-99224 (IC(50)=45 microM) inhibited in vitro PRP aggregation in a concentration-related manner. 5. CS-747 prevented thrombus formation in a dose-related manner with an ED(50) value of 0.68 mg kg(-1). CS-747 was more potent than clopidogrel (6.2 mg kg(-1)) and ticlopidine (>300 mg kg(-1)). 6. CS-747, clopidogrel, and ticlopidine prolonged the bleeding time. The order of potency of these agents in this activity was the same as that in antiaggregatory and antithrombotic activities. 7. These findings indicate that CS-747 is an orally active and a potent antiplatelet and antithrombotic agent with a rapid onset and long duration of action, and warrants clinical evaluations of the agent.

In vitro inhibition of the cytochrome P450 (CYP450) system by the antiplatelet drug ticlopidine: potent effect on CYP2C19 and CYP2D6

AIMS

To examine the potency of ticlopidine (TCL) as an inhibitor of cytochrome P450s (CYP450s) in vitro using human liver microsomes (HLMs) and recombinant human CYP450s.

METHODS

Isoform-specific substrate probes of CYP1A2, 2C19, 2C9, 2D6, 2E1 and 3A4 were incubated in HLMs or recombinant CYPs with or without TCL. Preliminary data were generated to simulate an appropriate range of substrate and inhibitor concentrations to construct Dixon plots. In order to estimate accurately inhibition constants (Ki values) of TCL and determine the type of inhibition, data from experiments with three different HLMs for each isoform were fitted to relevant nonlinear regression enzyme inhibition models by WinNonlin.

RESULTS

TCL was a potent, competitive inhibitor of CYP2C19 (Ki = 1.2 +/- 0.5 microM) and of CYP2D6 (Ki = 3.4 +/- 0.3 microM). These Ki values fell within the therapeutic steady-state plasma concentrations of TCL (1-3 microM). TCL was also a moderate inhibitor of CYP1A2 (Ki = 49 +/- 19 microM) and a weak inhibitor of CYP2C9 (Ki > 75 microM), but its effect on the activities of CYP2E1 (Ki = 584 +/- 48 microM) and CYP3A (> 1000 microM) was marginal.

CONCLUSIONS

TCL appears to be a broad-spectrum inhibitor of the CYP isoforms, but clinically significant adverse drug interactions are most likely with drugs that are substrates of CYP2C19 or CYP2D6.