Pharmacokinetic and clinical data supporting the use of fondaparinux 1.5 mg once daily in the prevention of venous thromboembolism in renally impaired patients

Anticoagulants in Children with Renal Impairment: A Narrative Review

Venous thromboembolism is a common cause of morbidity and mortality in children with renal disease. To properly treat and prevent thromboembolism in this patient population, it is important to be familiar with the multitude of anticoagulant agents currently available. Many anticoagulant drugs undergo some extent of renal elimination. There are important considerations for the selection, dosing, and monitoring of anticoagulant drugs for patients with renal impairment due to various pharmacokinetic alterations that may occur. While there are data to help guide dosing and monitoring in adults, evidence regarding renal dose adjustment of many anticoagulant drugs in children are limited. For the clinician, anticoagulation management in children with renal impairment presents unique challenges. In addition to considering overall bleeding risk, the extent of renal impairment may vary by patient, making a one-size-fits-all approach to managing these patients difficult. These factors, combined with limited data, can make managing anticoagulation in children with renal impairment a challenge. Therefore, the focus of this review will be to describe the pharmacokinetics of the following anticoagulants in children with impaired renal function: unfractionated heparin, enoxaparin, dalteparin, rivaroxaban, apixaban, edoxaban, fondaparinux, bivalirudin, argatroban, dabigatran, and warfarin.

Prevalence and Risk Factors of Inappropriate Drug Dosing among Older Adults with Dementia or Cognitive Impairment and Renal Impairment: A Systematic Review

Background: Potentially inappropriate medication prescribing is prevalent and well studied in older adults. However, limited data are available on inappropriate drug dosing in those with dementia or cognitive impairment and renal impairment. Objectives: We aimed to examine the prevalence of, and factors associated with, inappropriate drug dosing in older patients with dementia or cognitive impairment and renal impairment. Methods: We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline and the Cochrane Handbook for Systematic Reviews of Interventions. We searched Medline, Embase, CINAHL, and PubMed for studies on inappropriate drug dosing in older patients with dementia or cognitive impairment and renal impairment, published from 1 January 2000 to 31 August 2024, with English language restriction following the PICOS search strategy. Two reviewers independently screened all titles and abstracts, extracted data from included studies, and undertook quality assessment using the Joanna Briggs Institute (JBI) tool. Descriptive statistics were used to summarise and present findings. Results: In total, eight retrospective cohort studies were included. Of the total number of patients with dementia who had renal impairment (n = 5250), there were 2695 patients (51.3%; range: 0-60%) who had inappropriate drug dosing. Drugs commonly prescribed in inappropriate doses in patients with dementia who had renal impairment included memantine, baclofen, nonsteroidal anti-inflammatory drugs (NSAIDs), metformin, digoxin, morphine, and allopurinol. The studies did not identify statistically significant risk factors for inappropriate drug dosing. Conclusions: Inappropriate drug dosing among older adults with dementia or cognitive impairment and renal impairment appears to occur frequently. While our findings should be interpreted with caution owing to the small number of studies and substantial heterogeneity, proactive prevention, recognition, and management of inappropriate drug dosing in this population is warranted.

Incidence and risk factors of major bleeding following major orthopaedic surgery with fondaparinux thromboprophylaxis. A time-to-event analysis

AIMS

Increased exposure to fondaparinux, as observed in patients with renal impairment, may increase bleeding risk. This study aims to determine the time course of major bleeding after major orthopaedic surgery, identify predictors of bleeding and simulate the effect of a reduced dose of fondaparinux on bleeding for patients with moderate renal impairment (creatinine clearance = 20-50 ml min^-1 ).

METHODS

Data including fondaparinux anti-Xa activities from two multicentre prospective cohorts were used. In the first cohort, patients (n = 957) received fondaparinux 2.5 mg once a day. In the second, patients with moderate renal impairment (n = 436) received 1.5 mg once per day. The time-to-major bleeding after the end of surgery was modelled using a parametric survival analysis in NONMEM.

RESULTS

The observed rate of major bleeding up to day 11 was 5.2%. The time-to-event analysis indicated that the hazard of bleeding was highest in the first days following surgery and then remained low thereafter. Independent significant predictors of an increased hazard of major bleeding were male sex, lower body weight and increased drug exposure. Simulated rates of major bleeding up to day 11 in patients with moderate renal impairment were 6.5% with fondaparinux 2.5 mg once daily and 3.8% with fondaparinux 1.5 mg once daily.

CONCLUSION

The hazard of major bleeding is highest in the first postoperative days and increases with fondaparinux exposure. To reduce the risk of bleeding in patients with moderate renal impairment, this study supports the use of a lower dose of fondaparinux 1.5 mg once daily.

Assessment of an Extended Interval Fondaparinux Dosing Regimen for Venous Thromboembolism Prophylaxis in Critically Ill Patients with Severe Renal Dysfunction Using Antifactor Xa Levels

OBJECTIVE

Pharmacologic options for venous thromboembolism (VTE) prophylaxis are often limited in critically ill patients due to thrombocytopenia and multisystem organ dysfunction. Fondaparinux offers potential advantages in the critically ill; however, it is currently contraindicated in severe renal dysfunction (SRD). We evaluated anti-factor Xa levels in critically ill patients with SRD who were receiving an extended interval dosing regimen of fondaparinux for VTE prophylaxis.

METHODS

A prospective, single-arm, interventional study was conducted at two academic hospitals of the Detroit Medical Center. Eligible patients were in the intensive care unit, had an estimated creatinine clearance of less than 30 ml/minute, and had either acute kidney injury or end-stage renal disease; several patients were taking renal replacement therapy. Fondaparinux was administered at an extended interval dosing regimen of 2.5 mg subcutaneously every 48 hours. Fondaparinux peak and trough anti-factor Xa levels were obtained. Lower extremity venous duplex studies were performed at baseline and study completion to assess for deep vein thrombosis (DVT), and patients were monitored for bleeding complications.

RESULTS

Thirty-two patients were enrolled. Patients received a median of four doses (interquartile range two to five) of fondaparinux. Fondaparinux peak (n=98) and trough (n=86) anti-factor Xa levels were 0.36 ± 0.18 mg/L and 0.17 ± 0.11 mg/L (mean ± SD), respectively, and were similar to levels reported in patients with normal renal function receiving conventional once-daily dosing. No lower extremity DVTs or suspected VTE events occurred. Two (6%) patients had significant bleeding events.

CONCLUSIONS

In critically ill patients with SRD, an extended interval fondaparinux dosing regimen of 2.5 mg every 48 hours for VTE prophylaxis achieved peak and trough anti-factor Xa levels similar to those reported in noncritically ill patients with normal renal function receiving once-daily fondaparinux. This regimen offers an alternative for patients with SRD when heparinoids must be avoided.

Venous thromboembolism prevention with fondaparinux 1.5 mg in renally impaired patients undergoing major orthopaedic surgery

Despite the need for effective and safe thromboprophylactic drugs for patients with renal impairment, clinical trial data on anticoagulant agents are limited in this population. The study aim was to assess in the real-world setting the use of the once-daily 1.5 mg reduced dosage regimen of fondaparinux available for this context. In this prospective cohort study, patients with a creatinine clearance (CrCl) of 20–50 ml/ minute, undergoing total hip (THR) or knee (TKR) replacement or hip fracture surgery (HFS) received fondaparinux thromboprophylaxis. Main clinical outcomes were bleeding (major/clinically relevant nonmajor), symptomatic venous thromboembolism (VTE) and death. Overall, 442 patients (353 women; median age: 82 years; 39.4% in ASA class ≥3; mean ± SD CrCl: 39.0 ± 8.0 ml/minute; 78% with additional risk factors for bleeding), undergoing THR (43.7%), TKR (27.6%), or HFS (28.7%) received fondaparinux 1.5 mg for a mean ± SD duration of 16.0 ± 12.5 days. At postoperative day 10, the rates (95% confidence interval) of major bleeding, clinically relevant bleeding and symptomatic VTE were 4.5% (2.8–6.9), 0.5% (0.1–1.6) and 0.5% (0.05–1.62), respectively; no fatal bleeding, bleeding into a critical organ, pulmonary embolism or proximal deep-vein thrombosis occurred. Corresponding rates at one month were 5.2%, 0.7% and 0.7%. One-month mortality was 2.3% (0.9–3.6). This large clinical prospective study provides for the first time, under conditions reflecting “real-world” routine clinical practice, data on the bleeding and VTE risks of thromboprophylaxis with fondaparinux 1.5 mg after major orthopaedic surgery in renally impaired patients. It shows that these patients constitute a very elderly and fragile population.

ClinicalTrials.gov number, NCT00555438

Anticoagulation Therapy in Patients with Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are at increased risk for both thrombotic events and bleeding. The early stages of CKD are mainly associated with prothrombotic tendency, whereas in its more advanced stages, beside the prothrombotic state, platelets can become dysfunctional due to uremic-related toxin exposure leading to an increased bleeding tendency. Patients with CKD usually require anticoagulation therapy for treatment or prevention of thromboembolic diseases. However, this benefit could easily be offset by the risk of anticoagulant-induced bleeding. Treatment of patients with CKD should be based on evidence from randomized clinical trials, but usually CKD patients are excluded from these trials. In the past, unfractionated heparins were the anticoagulant of choice for patients with CKD because of its independence of kidney elimination. However, currently low-molecular-weight heparins have largely replaced the use of unfractionated heparins owing to fewer incidences of heparin-induced thrombocytopenia and bleeding. We undertook this review in order to explain the practical considerations for the management of anticoagulation in these high risk population.

Guidance to develop individual dose recommendations for patients on chronic hemodialysis

INTRODUCTION

In addition to tailored clinical trials in patients on chronic hemodialysis (HD) during drug development, clinician-initiated post-marketing studies and case reports on individual pharmacokinetic (PK) assessments provide an important source of information about drug dialysability and individualized dose recommendations in this vulnerable population. Areas covered: First, factors that may alter drug exposure in HD patients are explained. Second, available regulatory and methodological guidelines for PK assessments in this population are summarized. Third, a 4-step approach is proposed to develop individual dose recommendations for HD patients receiving drugs without data from a PK study: (1) literature search, (2) model-based dosage decisions, (3) validation and refinement through concentration monitoring, and (4) publication of relevant observations. Fourth, clinician-initiated PK assessments and case reports to evaluate and individualize use of drugs in HD patients are reviewed, and recommendations to enhance their quality are discussed. Expert commentary: Guidance on collecting and reporting PK information in individual HD patients is warranted to ensure completeness and consistency of such PK studies. A checklist and template for easy-to-implement PK calculations and pharmacometric modeling is provided to facilitate evaluation and individualization of dosing strategies in these patients.

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux.

Evaluation of Factor Xa-Specific Chromogenic Substrate Assays and the Determination of Pharmacokinetics of Fondaparinux

Fondaparinux (FPX), a synthesized factor Xa inhibitor, is one of the most popular anticoagulants for the prevention of postoperative venous thromboembolism (VTE). Although routine monitoring is not required, the bleeding adverse events cannot be neglected, and the measurement of anti-Xa activity is expected to be monitored. The primary purpose of this study is to evaluate the performances of 2 chromogenic assays for the detection of anti-Xa activity. Furthermore, the pharmacokinetics of FPX was examined using chromogenic assays. Anti-Xa activity was measured using 2 FPX-based chromogenic substrates (S2222 and STA-Liquid Anti-Xa). The reproducibility, detection limits, linearity, and correlations between the substrates were examined using normal plasma doped with low and high concentrations of FPX formulation. In addition, anti-Xa activity in 235 clinical samples from 164 cases treated was measured, and the pharmacokinetics of FPX was evaluated. Both of the tested substrates were capable of accurately measuring the anti-Xa activity of FPX, with a lower limit of 0.05 μg/mL and a coefficient of variation of less than 10%. The repeated administration of FPX induced a gradual but significant increase in the anti-Xa activity, which was negatively correlated with body weight and estimated glomerular filtration rate. No significant correlation between the anti-Xa activity and the occurrence of postoperative VTE or bleeding event was observed. Anti-Xa activity can be successfully determined using 2 chromogenic assays and automated biochemical analyzers. The clinical significance of anti-Xa activity monitoring should be examined in the future study.

Anticoagulant dosing in renal impairment

Anticoagulants are widely used for prophylaxis and treatment of venous thromboembolism in the elderly, who commonly have renal impairment and other comorbidities. Renal impairment is a risk factor for bleeding and thrombosis during anticoagulant therapy and can influence the balance between the safety and efficacy of such agents. Some anticoagulants, such as fondaparinux and the direct acting oral thrombin inhibitor dabigatran etexilate are contraindicated for use in patients with severe renal impairment (eGFR <30 ml/min). However, also the direct acting oral FXa-inhibitors rivaroxaban, edoxaban and apixaban need caution regarding dosing advice or contraindications when used in patients with renal impairment.

Considerations for Systemic Anticoagulation in ESRD

In the setting of end-stage kidney disease, the incidence and risk for thrombotic events are increased and use of anticoagulants is common. The incidence of bleeding, however, is also a frequent issue and creates additional challenges in the management of anticoagulation therapy. Patients with end-stage renal disease are typically excluded from large clinical trials exploring the use of anticoagulants, which limits our knowledge of optimal management approaches. Furthermore, varying degrees of renal failure in addition to conditions that alter the pharmacokinetics of various anticoagulants or pharmacodynamic response may warrant alternative approaches to dosing. This review will explore systemic chronic anticoagulation therapy in the setting of chronic kidney disease where hemodialysis is required. Agents discussed include vitamin K antagonists, low-molecular-weight heparins, fondaparinux, oral factor Xa antagonists, and direct thrombin inhibitors. Clinical challenges, approaches to dosing regimens, and tools for measuring responses and reversal will be explored.

Clinical experience with prophylactic fondaparinux in critically ill patients with moderate to severe renal impairment or renal failure requiring renal replacement therapy

BACKGROUND

Fondaparinux has an increased bleeding risk in patients with a CrCl ≤ 50 mL/min and is contraindicated if CrCl < 30 mL/min. Data regarding dosing and anti-Xa monitoring are lacking in this population.

OBJECTIVE

To describe dosing, monitoring, and safety outcomes of prophylactic fondaparinux in critically ill patients with moderate to severe renal impairment, including renal replacement therapy (RRT).

METHODS

Retrospective analysis from October 2006 to November 2012 of patients ≥ 18 years old who received fondaparinux for ≥ 72 hours with ≥ 1 dose in an intensive care unit and a CrCl ≤ 50 mL/min or RRT during therapy. Participants were divided into 4 cohorts: moderate impairment (CrCl = 30-50 mL/min), severe impairment (CrCl < 30 mL/min), hemodialysis (HD), or continuous venovenous hemofiltration (CVVH). Outcomes included the incidence of clinically significant bleeding and thromboembolic events. Fondaparinux dose, dosing frequency, and anti-Xa level monitoring are described. Pharmacokinetic modeling was performed to assess drug accumulation.

RESULTS

In all, 95 patients met inclusion criteria: 64 (67.4%) with moderate impairment, 10 (10.5%) with severe impairment, 5 (5.3%) with HD, and 16 (16.8%) with CVVH. The median defined daily doses in the moderate, severe, HD, and CVVH cohorts were 2.5, 2.5, 0.9, and 1.9 mg. Anti-Xa monitoring occurred in 19 (20%) patients, although few concentrations were peaks. Clinically significant bleeding occurred in 4 (4.2%) patients. A pharmacokinetic model demonstrated drug accumulation.

CONCLUSIONS

Empirical dose adjustments may be prudent in critically ill patients with renal dysfunction; however, the optimal fondaparinux dosage in this population remains unknown. Peak anti-Xa concentrations may help guide therapy.

Thromboprophylaxis with fondaparinux in high-risk postoperative patients with renal insufficiency

Fondaparinux is an antithrombin-dependent factor Xa inhibitor that is used for thromboprophylaxis of patients undergoing hip fracture surgery, hip or knee replacement, or abdominal surgery. It is cleared by the kidney and should be used with caution in patients with renal impairment and avoided in patients with severe renal insufficiency. Recently, several studies have demonstrated that a lower dose of fondaparinux in patients with moderate renal impairment appears to be safe and effective. The purpose of this study was to obtain pharmacokinetic and clinical data on the use of prophylactic fondaparinux in patients with renal insufficiency undergoing major abdominal surgery for cancer (n=8) or orthopedic surgery (n=1). Anti-factor Xa levels were obtained, and a published population pharmacokinetic model for fondaparinux was fit to the data. The data were analyzed using NONMEM software. Fondaparinux did not appear to accumulate in these patients, even when the drug was administered for up to twelve days. Pharmacokinetic analysis revealed that the apparent clearance in this population, who were primarily undergoing cancer surgery, was similar to prior studies in orthopedic surgery patients. In contrast, lower estimates were obtained for volume of distribution and absorption rate constant parameters. None of the patients sustained a hemorrhagic complication attributable to fondaparinux. One patient developed hypoxia in the setting of transient atrial fibrillation and clinical suspicion for pulmonary embolism, but this was not confirmed radiographically. These results support the use of 1.5mg of fondaparinux every 24hours for thromboprophylaxis in patients with renal insufficiency undergoing high-risk surgical procedures.

Safety and efficacy of low-dose fondaparinux (1.5 mg) for the prevention of venous thromboembolism in acutely ill medical patients with renal impairment: the FONDAIR study

BACKGROUND

Renal impairment is common, affecting around 40% of acutely ill medical patients, and is associated with an increased risk of both venous thromboembolism (VTE) and bleeding. The clinical benefit of effective thromboprophylactic strategies may be outweighed in these patients by an excessive rate of hemorrhage.

OBJECTIVE

To assess the safety and efficacy of lower prophylactic doses of fondaparinux in acutely ill medical patients with renal impairment.

PATIENTS/METHODS

We carried out a multicenter, investigator-initiated, prospective cohort study. Patients at risk of VTE with a creatinine clearance between 20 and 50 mL min(-1) were treated with fondaparinux 1.5 mg qd for a minimum of 6 to a maximum of 15 days. The primary outcome was the incidence of major bleeding; secondary outcomes were clinically relevant non-major bleeding (CRNMB) and symptomatic VTE.

RESULTS

We enrolled 206 patients with a mean age of 82 years, mean creatinine clearance of 33 mL min(-1) , and a mean Charlson co-morbidity index of 8.2. One patient had major bleeding (0.49%, 95% confidence interval [CI] 0.03-3.10), eight had CRNMB (3.88%, 95% CI 1.81-7.78) and three developed symptomatic VTE (1.46%, 0.38-4.55). Twenty-three patients (11.17%, 7.36-16.48) died. No independent predictors of bleeding were found at univariate analysis.

CONCLUSIONS

The addition of moderate to severe renal impairment to patients with traditional risk factors for VTE identified a population of very elderly acutely ill medical patients potentially at high risk of both VTE and bleeding complications. The recently approved lower prophylactic dose of fondaparinux appears to be a safe and relatively effective strategy in these patients.

Pharmacokinetics of fondaparinux 1.5 mg once daily in a real-world cohort of patients with renal impairment undergoing major orthopaedic surgery

PURPOSE

Fondaparinux, a selective activator factor X (factor Xa) inhibitor, is effective and safe for preventing venous thromboembolism after major orthopaedic surgery (MOS) at the once-daily subcutaneous dose of 2.5 mg. As the drug is mainly eliminated by the kidneys, a reduced dosage (1.5 mg once daily) was developed for patients with renal impairment.

METHODS

We studied the pharmacokinetics (PK) of this dosage regimen using data from a real-world cohort of 442 patients with renal impairment (creatinine clearance 20-50 ml/min) undergoing MOS. Data were analysed using NON-linear Mixed Effect Modelling software (NONMEM) software. Fondaparinux PK was modelled using a two-compartment model with first-order absorption.

RESULTS

This analysis confirmed the relationship between renal function and fondaparinux PK profiles. The mean predicted steady-state area under the plasma concentration time curve, peak and trough plasma concentrations of fondaparinux were lower by 15.6 %, 13.0 % and 10.3 %, respectively, in patients with renal impairment treated with 1.5 mg compared with patients with normal renal function treated with 2.5 mg (p < 0.01).

CONCLUSION

Although administration of 1.5 mg fondaparinux in patients with renal impairment resulted in a predicted exposure slightly lower than that achieved with 2.5 mg in patients with normal renal function, fondaparinux 1.5 mg is a valuable thromboprophylactic option in MOS patients with renal impairment who are at risk of bleeding.

Fondaparinux - data on efficacy and safety in special situations

New anticoagulants promise to have better efficacy, more safety and/or a better manageability than traditional anticoagulants. However, knowledge is limited regarding special situations such as renal insufficiency, obesity, pregnancy, long-term therapy, heparin-induced thrombocytopenia, treatment in patients with mechanical heart valves, use for children, and in patients with a high risk of thromboembolic complications. These situations have rarely or even never been the objective of randomised controlled trials. The purpose of the present article is to summarize and discuss available data on efficacy and safety in these special situations for one of the first new anticoagulants, the indirect factor-Xa inhibitor fondaparinux. Furthermore, we discuss safety in licensed indications and management of bleeding complications and comment on measuring of drug concentration in plasma.

Thromboprophylaxis in patients older than 75 years or with moderate renal impairment undergoing knee or hip replacement surgery [corrected]

PURPOSE

Prospective, double-blind studies in orthopaedic patients have been conducted using the direct thrombin inhibitor dabigatran etexilate (hereafter referred to as dabigatran), with two doses investigated and approved for adults (220 mg and 150 mg once daily) to prevent venous thromboembolism (VTE). The European Medicines Agency decided that in major joint orthopaedic surgery, the lower dose should be used in elderly patients (aged over 75 years) and those with reduced renal function (creatinine clearance between 30 and 50 ml/min). Our objective was to understand the efficacy and bleeding data for the lower dose in this subpopulation.

METHODS

We extracted and analysed data from the elderly or from moderately renally impaired patients (n 632 of = 5,539) from the orthopaedic clinical development programme of dabigatran.

RESULTS

Dabigatran 150 mg once daily was as effective as the standard European enoxaparin regimen, with numerically fewer major bleeding events. Rates of major VTE were 4.3% vs 6.4% of patients, respectively. Major bleeding events occurred in four (1.3%) vs 11 (3.3%), which shows a trend towards lower bleeding with dabigatran 150 mg [odds ratio (OR) 0.40; 95% confidence interval (CI) 0.13-1.25; p = 0.110]. Mean volume of blood loss was 395 vs 417 ml, and transfused units were 2.4 vs 2.5, respectively. Other safety parameters, including the incidence of wound infections and complications, were similar for 150 mg once daily dabigatran and enoxaparin.

CONCLUSION

For patients at higher risk of bleeding, dabigatran 150 mg once daily is as effective as enoxaparin following major orthopaedic surgery and is associated with a favourable bleeding rate.

Areas of uncertainty in prophylaxis of venous thromboembolism in unselected subjects

In the last decade, parenteral anticoagulants have proven to be effective in the prevention of venous thromboembolism (VTE) in patients admitted to hospitals. Despite this, some registry studies have shown that pharmacological prophylaxis is still widely underused. We performed a literature search to identify important knowledge gaps in the use of VTE prophylaxis that were not addressed by previous published reports. MEDLINE and HighWire databases covering the years 1999-2009 were searched; only clinical trials of unselected adult subjects were included. Two reviewers independently selected studies and extracted data on inclusion and exclusion criteria, age, weight, comorbidities, study designs, and endpoints. Five of 113 relevant studies were identified from the literature search. Knowledge gaps were disclosed in subject inclusion, exclusion, and stratification regarding young age, under- and overweight, comorbidities, and the selection of clinically significant endpoints. Uncertainties in the dosage, risk stratification of subjects, and effect on hard endpoints as prevention of pulmonary embolism or reduction of mortality reduce the impact of VTE prevention clinical trials.

Role of factor xa inhibitors in cancer-associated thrombosis: any new data?

The association between cancer and venous thromboembolism (VTE) has been well documented in the literature. Prevention and treatment of VTE in cancer patients is imperative. Typically, the mainstay regimen for VTE prevention and treatment has been anticoagulation therapy, unless contraindicated. This therapy consists of unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), factor Xa inhibitor, or vitamin K antagonist (VKA). Current guidelines recommend LMWH over VKA for the treatment of VTE in cancer patients. Factor-specific anticoagulants have been proven safe and effective, and recently factor Xa inhibitors have emerged as a treatment alternative to heparins and VKA. Currently, three factor Xa inhibitors have been identified: fondaparinux (the only one approved so far by the US Food and Drug Administration), idraparinux (in clinical trials), and idrabiotaparinux (in clinical trials). This paper will examine the role of these agents, focusing on fondaparinux, for the prevention and treatment of VTE in cancer patients.

Fondaparinux: does it cause HIT? Can it treat HIT?

Heparin-induced thrombocytopenia (HIT) is an antibody-mediated prothrombotic disorder triggered by PF4-binding polyanions, usually heparin. The pentasaccharide anticoagulant, fondaparinux, despite its negative charge and structural similarity to heparin, does not usually promote antibody binding to PF4 (owing to absent/weak 'cross-reactivity'). Thus, despite its ability to trigger anti-PF4/heparin antibodies ('immunogenicity'), fondaparinux has low - but not zero - risk of inducing HIT de novo, or of exacerbating HIT when antibodies are already present. Indeed, despite rare reports of fondaparinux-induced HIT, this 'dissociation' between immunogenicity and cross-reactivity suggests that fondaparinux should be effective in treating HIT, as supported by several observational studies. An emerging issue: will clinicians accept this favorable experience of fondaparinux for treating HIT when a lack of randomized trials will hinder regulatory approval for this indication?

Anticoagulation in the Elderly

Management of anticoagulation in elderly patients represents a particularly challenging issue. Indeed, this patient population is at high thromboembolic risk, but also at high hemorrhagic risk. Assessment of the benefit-risk balance of anticoagulation is the key point when decisions are made about introducing and/or continuing such treatments in the individual elderly patient. In order to maximise the safety of anticoagulation in the elderly, some specific considerations need to be taken into account, including renal insufficiency, modified pharmacodynamics of anticoagulants, especially vitamin K antagonists, and the presence of multiple comorbidities and concomitant medications. New anticoagulants could greatly simplify and possibly increase the safety of anticoagulation in the elderly in the near future.

Systemic anticoagulation considerations in chronic kidney disease

Anticoagulation therapy is commonly required in patients with chronic kidney disease for treatment or prevention of thromboembolic disorders. Anticoagulant management plans can involve use of a single agent, or in some cases, a combination of agents to meet both short- and long-term goals. Systemic anticoagulation in the setting of renal insufficiency poses unique challenges secondary to renal failure-associated hypercoagulable conditions and increased risks for bleeding. Evidence supporting dosing regimens and monitoring approaches in the setting of severe renal impairment or hemodialysis is limited because this population is typically excluded in clinical trials. This review explores concepts of systemic anticoagulation in the chronic kidney disease setting with warfarin, unfractionated heparin, low-molecular-weight heparin, fondaparinux, direct thrombin inhibitors, and anticoagulants in advanced stages of development. Potential strategies for anticoagulant reversal are also briefly described.