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

Appropriateness of antiplatelet therapy for primary and secondary cardio- and cerebrovascular prevention in acutely hospitalized older people

AIMS

Antiplatelet therapy is recommended for the secondary prevention of cardio- and cerebrovascular disease, but for primary prevention it is advised only in patients at very high risk. With this background, this study aims to assess the appropriateness of antiplatelet therapy in acutely hospitalized older people according to their risk profile.

METHODS

Data were obtained from the REPOSI register held in Italian and Spanish internal medicine and geriatric wards in 2012 and 2014. Hospitalized patients aged ≥65 assessable at discharge were selected. Appropriateness of the antiplatelet therapy was evaluated according to their primary or secondary cardiovascular prevention profiles.

RESULTS

Of 2535 enrolled patients, 2199 were assessable at discharge. Overall 959 (43.6%, 95% CI 41.5-45.7) were prescribed an antiplatelet drug, aspirin being the most frequently chosen. Among patients prescribed for primary prevention, just over half were inappropriately prescribed (52.1%), being mainly overprescribed (155/209 patients, 74.2%). On the other hand, there was also a high rate of inappropriate underprescription in the context of secondary prevention (222/726 patients, 30.6%, 95% CI 27.3-34.0%).

CONCLUSIONS

This study carried out in acutely hospitalized older people shows a high degree of inappropriate prescription among patients prescribed with antiplatelets for primary prevention, mainly due to overprescription. Further, a large proportion of patients who had had overt cardio- or cerebrovascular disease were underprescribed, in spite of the established benefits of antiplatelet drugs in the context of secondary prevention.

Characterization of ticlopidine-induced developmental and teratogenic defects in Xenopus embryos and human endothelial cells

Ticlopidine is an anti-platelet drug that inhibits platelet aggregation via the functional alteration of platelet membranes. However, the mechanism underlying the adverse developmental effects of ticlopidine has not been clearly demonstrated. In this study, we evaluated the developmental toxicity and teratogenicity of ticlopidine on Xenopus laevis embryos and in human umbilical vein endothelial cells (HUVECs) using a frog embryo teratogenesis assay-Xenopus (FETAX) and blood and lymph vessel formation assays. Ticlopidine induced teratogenicity and inhibited growth, as evidenced by mortality rates and embryo lengths, respectively. Moreover, ticlopidine induced severe hemorrhages and inhibited both blood and lymph vessel formation by modulating the expression of xMsr and Prox1 in Xenopus embryos. Additionally, Nkx2.5 and Cyl104 levels were perturbed by ticlopidine exposure, and more extensive aberrations were observed in the liver and heart using whole-mount in situ hybridization. In addition, ticlopidine reduced branching in HUVECs by blocking the effect of the angiogenic vascular endothelial growth factor (VEGF). Results from this study suggest that ticlopidine is a developmental toxicant and teratogen and therefore this is a step forward in our understanding of the effects of ticlopidine during developmental processes.

Effects of cilostazol on the progression and regression of symptomatic intracranial artery stenosis: it reduces the risk of ischemic stroke

OBJECTIVE:

To assess the efficacy and safety of cilostazol on the progression and regression of symptomatic intracranial artery stenosis.

DATA RETRIVAL:

We searched the main databases for eligible trials including Medline (from 1966 to June 2014), Embase (from 1980 to June 2014), Cochrane Library (Issue 6, 2014), Chinese National Knowledge Infrastructure (from 1995 to June 2014), Current Controlled Trials (http://controlled-trials.com), Clinical Trials.gov (http://clinicaltrials.gov), and Chinese Clinical Trial Registry (http://www.chictr.org). All studies regarding prevention and treatment of symptomatic intracranial arterial stenosis by cilostazol were collected. The Mesh or text keywords were the English words: “cilostazol, phosphodiesterase 3 inhibitor, atherosclerosis, and ischemic stroke.” No restrictions were put on publications or publication language.

SELECTION CRITERIA:

Grade A or B randomized controlled trials were selected according to the quality of evaluation criteria from the Cochrane Collaboration, in which cilostazol and aspirin were used to evaluate the effects of cilostazol in the treatment of patients with symptomatic intracranial artery stenosis. The quality of study methodology was evaluated based on criteria described in Cochrane Reviewer's Handbook 5.0.1. RevMan 5.2 software was used for data analysis.

MAIN OUTCOME MEASURES:

Clinical efficacy and safety of cilostazol in stopping progression and promoting regression of symptomatic intracranial artery stenosis were measured by magnetic resonance angiography and transcranial Doppler.

RESULTS:

Two randomized controlled trials with a total of 203 patients were included in this study. The results showed that while cilostazol was associated with a significantly reduced progression of intracranial artery stenosis (OR = 0.21, 95%CI: 0.09–0.47, P < 0.01), it had no beneficial effect on symptom regression (OR = 1.42, 95%CI: 0.80–2.51, P = 0.24). During the follow-up period, although some adverse effects developed, including headache, gastrointestinal disturbance, and dizziness, incidences of bleeding were lower than in aspirin-treated patients.

CONCLUSION:

Cilostazol may prevent the progression of symptomatic intracranial artery stenosis, which could reduce the incidence of ischemic stroke.

Is there an alternative to systemic anticoagulation, as related to interventional biomedical devices?

To reduce the toxic effects, related clinical problems and complications such as bleeding disorders associated with systemic anticoagulation, it has been hypothesized that by coating the surfaces of medical devices, such as stents, bypass grafts, extracorporeal circuits, guide wires and catheters, there will be a significant reduction in the requirement for systemic anticoagulation or, ideally, it will no longer be necessary. However, current coating processes, even covalent ones, still result in leaching followed by reduced functionality. Alternative anticoagulants and related antiplatelet agents have been used for improvement in terms of reduced restenosis, intimal hyperphasia and device failure. This review focuses on existing heparinization processes, their application in clinical devices and the updated list of alternatives to heparinization in order to obtain a broad overview, it then highlights, in particular, the future possibilities of using heparin and related moieties to tissue engineer scaffolds.

Systematic study of cilostazol on secondary stroke prevention: a meta-analysis

BACKGROUND

To study the efficacy and safety of cilostazol on ischemic stroke prevention and treatment, systematic reviews of related clinical randomized controlled trials were analyzed.

METHODS

We searched the main databases for eligible trials including literature from January 1966 to November 2012 in MEDLINE, reports from 1980 to November 2012 in EMBASE, and all the studies published in EBSCO, Springer, Ovid, and Cochrane library citations. We also searched for keywords, including cilostazol and aspirin. RewMan 5.0 software was used to conduct the meta-analysis.

RESULTS

Our search yielded five eligible trials. The effects of cilostazol and aspirin on ischemic stroke prevention and treatment were almost equal (combined odds ratio (OR) 0.78, 95% confidence interval (CI) (0.59, 1.04)). Additionally, both magnetic resonance angiography (MRA) and transcranial Doppler (TCD) examination showed that cilostazol could significantly decrease the incidence of intracranial artery stenosis exacerbation (MRA: combined OR 0.22, 95% CI (0.07, 0.68); TCD: combined OR 0.17, 95% CI (0.05, 0.51)). In terms of adverse reactions, there were slightly fewer incidences of major bleeding with cilostazol than with aspirin (combined OR 0.38, 95% CI (0.24, 0.60)), and there was no difference in the number of heart palpitations between cilostazol and aspirin. However, the incidence of gastrointestinal disorders, dizziness, and headaches caused by cilostazol was greater.

CONCLUSIONS

Cilostazol might be a more effective and safer alternative to aspirin for patients with ischemic stroke. Further studies are required to confirm whether cilostazol is a suitable therapeutic option for secondary stroke prevention in larger cohorts of patients with ischemic stroke.

Anticoagulation Review

Anticoagulants, also known as antithrombotics, are among the most commonly prescribed medications in the United States. Understanding how these medications work, the propensity for interactions with other drugs, dietary factors, and disease states is important for clinicians assessing and providing care to patients in all environments. In this review, we seek to provide essential information for the home health care provider for evaluating patients receiving anticoagulants commonly prescribed in the home health care setting. The low-molecular-weight heparins and vitamin K antagonists are the most commonly used agents for outpatient anticoagulation. New agents, such as the direct factor Xa inhibitors and direct thrombin inhibitors have recently been approved with additional new agents in the approval process and development pipeline. We seek to review the most pertinent information for each of these classes of medications providing information on pharmacology, interactions with other drugs, diet, and diseases and important clinical information.

Our expanding view of platelet functions and its clinical implications

Platelets are the primary cell mediator of thrombosis. A deficiency of platelets can result in severe bleeding defects. "Overactive" platelets contribute to life-threatening outcomes in diseases such as heart attack, stroke, and cancer. The use of platelet inhibitors for thrombosis prevention must therefore seek a delicate balance between inhibiting platelet activation and an associated increased bleeding risk. There are currently few platelet inhibitors clinically available, making the search for novel anti-platelet drug targets a major research priority. Several newly identified pathways of platelet activation may hold hope in this area. In addition, important roles for platelets beyond hemostasis have been discovered. Platelets have recently been described as mediators of diverse inflammatory diseases such as arthritis, hepatitis, malaria, and atherosclerosis. This has heightened the need to broaden our understanding of platelet functions and platelet-derived inflammatory mediators. It has also heightened interest in a continued search for new platelet inhibitors and presents new opportunities for platelet inhibitors to be used in a wide array of disease treatment strategies.

Prasugrel: newest antiplatelet agent and its emerging role in management of acute coronary syndrome and percutaneous coronary intervention

Oral antiplatelet therapy has been very effective in reducing vascular events. Currently available oral antiplatelet agents are aspirin and the thienopyridine P2Y(12)-receptor antagonists. These agents are used frequently in combination among patients with coronary artery disease, and also following percutaneous coronary intervention to reduce major adverse cardiovascular events. Emergence of resistance to either aspirin or clopidogrel, or both the agents, is a major concern as antiplatelet resistance is likely to increase thrombotic events, thus resulting in a worse clinical outcome. Development of new agents has therefore become imperative. Prasugrel is the newest thienopyridine with the most robust clinical data, and appears to be superior to clopidogrel, the most extensively used agent besides aspirin in contemporary cardiovascular practice. Possible advantages of prasugrel over clopidogrel are its faster onset of action, reduced inter-patient variability, and more potent and persistent platelet inhibition. This article summarizes the available clinical data on prasugrel in the treatment of coronary artery disease.

Hematopoietic growth factors in aplastic anemia patients treated with immunosuppressive therapy-systematic review and meta-analysis

Immunosuppressive therapy is the treatment for aplastic anemia patients ineligible for transplantation. The role of hematopoietic growth factors as adjunct to treatment in these patients is unclear. We conducted a systematic review and meta-analysis of randomized controlled trials comparing treatment with immunosuppressive therapy and hematopoietic growth factors to immunosuppressive therapy alone in patients with aplastic anemia. Two reviewers appraised the quality of trials and extracted data. For each trial, results were expressed as relative risks with 95% confidence intervals (CI) for dichotomous data. The addition of hematopoietic growth factors yielded no difference in overall mortality at 100 days, one year and five years [relative risks 1.33 (95% CI 0.56-3.18), relative risks 0.90 (95% CI 0.50-1.63) and relative risks 0.89 (95% CI 0.55-1.46), respectively]. There was no difference in overall hematologic response and in the occurrence of infections. HGF significantly decreased the risk for relapse, relative risks 0.45 (95% CI 0.30-0.68, 3 trials). Hematopoietic growth factors were not associated with higher occurrence of myelodysplastic syndrome and acute myeloid leukemia or paroxysmal nocturnal hemoglobinuria. The addition of hematopoietic growth factors does not affect mortality, response rate or infections occurrence. Therefore, it should not be recommended routinely as an adjunct to the immunosuppressive therapy for patients with aplastic anemia.

Neutropenia in patients treated with thienopyridines and high-dose oral prednisone after percutaneous coronary interventions

BACKGROUND

Oral treatment with prednisone has demonstrated efficacy in reducing restenosis after percutaneous coronary interventions (PCI). However, administration of steroids at high dose may raise concerns in terms of applicability and tolerability. Monitoring the occurrence of possible side-effects is therefore mandatory.

METHODS

Secondary effects of oral prednisone in this setting is analyzed. The "expected" secondary effects of the steroid treatment are described, together with the "unexpected" occurrence of likely drug-induced neutropenia observed in patients prescribed prednisone and thienopyridines simultaneously after PCI.

RESULTS

Two-hundred and twenty patients were monitored for the occurrence of side-effects of the prednisone therapy. Twenty-eight patients (14%) had side-effects likely related to the prednisone treatment: gastric pain (4%), increment of arterial pressure needing upgrading of antihypertensive treatment (4%), edema (1.8%), and concomitant infections (1.4%). In three patients (1.4%), agranulocytosis was detected at the time of the routine blood cell count scheduled 4 weeks after PCI in otherwise asymptomatic patients. Neutropenia subsided completely after withdrawal of prednisone and thienopyridine in all cases and the blood cell formula normalized within 3 weeks.

CONCLUSIONS

Side-effects of oral prednisone given after PCI to reduce restenosis occur in less than 15% of patients. Complaints are mild and reversible and can be easily managed with adjunctive diuretic and antacid drugs. The occurrence of agranulocytosis after prednisone had never been reported before, but was observed in 1.4% of our patients receiving simultaneously a thienopyridine. To explain such an unusual event we propose the hypothesis of a possible metabolic interaction between prednisone and thienopyridines.

Glucocorticoids in the prevention of restenosis after coronary angioplasty: therapeutic potential

Vessel luminal narrowing after percutaneous coronary intervention (PCI) is characterised by platelet aggregation, release of growth factors, inflammatory cell infiltration, medial smooth muscle cell (SMC) proliferation, proteoglycan deposition and extracellular matrix remodelling. It is broadly accepted that the central mechanism at the basis of the whole pathophysiological process of restenosis is inflammation, triggered by vascular injury and activated through autocrine or paracrine mediators. Glucocorticosteroids exert beneficial effects on platelet function, on SMC proliferation and on collagen synthesis as well as inflammatory cell migration and activation, thus interfering with several steps of the cascade leading to neointima formation and subsequent late lumen loss. Initial experiences with systemic administration of glucocorticoids after PCI failed to confirm the expected benefits of this treatment, probably as a result of inadequate dosage and pharmacokinetic calculations. Recently a short-term, high-dose immunosuppressive treatment scheme with oral prednisone has demonstrated remarkable clinical and angiographic results when prednisone was given orally at a dose of 1 mg/kg for 10 days, 0.5 mg/kg for 20 days and 0.25 mg/kg for 15 days. This treatment has dramatically reduced the incidence of clinical vascular events at 1 year compared with controls (relative risk 0.34; 95% CI 0.12, 0.96; p = 0.006) and reduced the incidence of angiographic restenosis below 10% in different clinical and angiographic subsets. Secondary effects of a short course of glucocorticoids are generally minor, predictable and reversible: gastric pain, water and salt retention and worsened hypertension manifest in nearly 10% of patients. The addition of diuretics and acid suppressants before discharge, and the upgrading of antihypertensive medication thereafter, if needed, are useful preventive measures to control these temporary disorders. A routine blood cell count 4 weeks after PCI is advised in patients receiving thienopyridines (clopidogrel or ticlopidine) in addition to prednisone to rule out infrequent haematological dyscrasias. Emerging evidence supports this strategy as a convenient and well tolerated alternative to more expensive and complex revascularisation procedures such as drug eluting stent (DES) implantation or cardiac surgery, provided that the treatment is reserved for carefully selected candidates, i.e. after the exclusion of those with diabetes mellitus, a recent transmural myocardial infarction, or contraindications to the administration of a short-course of high-dose glucocorticosteroids. The recent concerns regarding the long-term safety of first-generation DES and the as yet undetermined duration of dual anti-platelet treatment, further supports the need for a simple pharmacological treatment that can be applied in a large percentage of patients currently treated with PCI. Multicentre randomised studies aimed at defining the efficacy and safety of oral prednisone treatment compared with metallic stents and DES are ongoing, and will become available in upcoming years.

Benefits of clopidogrel in patients undergoing coronary stenting significantly depend on loading dose: evidence from a meta-regression

BACKGROUND

Clopidogrel is an established alternative to ticlopidine in addition to aspirin after coronary stenting because of its safety, but its optimal initial dosing is unclear. We performed a systematic review and meta-regression of randomized clinical trials comparing clopidogrel versus ticlopidine, focusing on clopidogrel front-loading.

METHODS

PubMed was searched for pertinent studies (updated August 2006). Random-effect odds ratios (ORs) with 95% CIs were computed for death or nonfatal myocardial infarction, and weighted least squares random-effect meta-regression was performed to explore the impact of loading versus nonloading clopidogrel scheme.

RESULTS

We retrieved 7 trials (3382 patients, average follow-up of 7 months). In 5 studies, both clopidogrel and ticlopidine were started with a loading dose, in 1 trial clopidogrel was administered without loading, and in 1 trial clopidogrel could be administered with or without loading. Overall analysis (P for heterogeneity = .02) showed similar results for clopidogrel and ticlopidine (OR 0.90, 95% CI 0.44-1.84, P = .77). In studies administering clopidogrel with loading, this treatment was, however, significantly better than ticlopidine (OR 0.60, 95% CI 0.36-0.99, P = .05). This significant interaction between clopidogrel loading and its superiority in comparison with ticlopidine was also formally confirmed by meta-regression (beta = -0.64, P = .012).

CONCLUSIONS

This work supports the superiority of a clopidogrel regimen including an initial loading dose in comparison with ticlopidine in patients undergoing coronary stenting.

Chemical toxicology: reactive intermediates and their role in pharmacology and toxicology

Reactive intermediates formed during the metabolism of drugs have been investigated extensively over the past decades. Today, interest in reactive intermediates in drug discovery is focused on minimising bioactivation in hopes of reducing the risk of causing so-called idiosyncratic toxicity. These efforts are justified based on the 'hapten hypothesis', namely, that on binding to protein, reactive intermediates may elicit an immune response to the modified protein, leading to a cascade of events that ultimately manifests as a toxic outcome. However, the pharmacological action of certain drugs depends on reactive intermediates that modify critical amino acid residues of proteins, typically enzymes, thereby altering their activity. Thus, the notion that reactive intermediates are inherently dangerous is unjustified. When a reactive intermediate is necessary for the desired pharmacological effect of a drug, the selectivity it displays towards the target protein is crucial, as off-target binding may produce unwanted toxicities. On the other hand, reactive intermediates may play no role in toxicity. This review provides a balanced perspective, primarily focusing on the proposed role of reactive intermediates in drug toxicity, while also highlighting examples in which they are involved in causing the desired pharmacology. It is hoped that this knowledge can help scientists involved in drug discovery and development in their challenging task of producing safe and effective drugs.