A systematic review on the accumulation of prophylactic dosages of low-molecular-weight heparins (LMWHs) in patients with renal insufficiency

Tinzaparin, an alternative to subcutaneous unfractionated heparin, in patients with severe and end-stage renal impairment: a retrospective observational single-center study

BACKGROUND

Tinzaparin could be easier to manage than unfractionated heparin in patients with severe renal impairment. However, clinical and pharmacologic data regarding its use in such patients are lacking.

OBJECTIVES

The aims of this study were to determine, in patients with estimated glomerular filtration rate (eGFR) of <30 mL.min⁻1, tinzaparin pharmacokinetics (PK) parameters using a population PK approach and bleeding and thrombotic complications.

METHODS

We performed a retrospective observational single-center study, including in-patients with eGFR of <30 mL.min⁻1 receiving prophylactic (4500 IU.d⁻1) or therapeutic (175 IU.kg⁻1.d⁻1) tinzaparin. Measured anti-Xa levels were analyzed using a nonlinear mixed-effects modeling approach. Individual predicted tinzaparin exposure markers at steady state were calculated for each patient and dosing regimen. The PK was also evaluated through Monte Carlo simulations based on the final covariate model parameter estimates.

RESULTS

Over a 22-month period, 802 tinzaparin treatment periods in 623 patients were analyzed: two-thirds received a prophylactic dose, 66% had an eGFR of <20 mL.min⁻1, and 25% were on renal replacement therapy. In patients for whom anti-Xa measurements were performed (n = 199; 746 values), PK parameters, profiles, and maximum plasma concentrations were comparable with those in patients without renal impairment or in healthy volunteers. In the whole population, major bleeding occurred in 2.4% and 3.5% of patients receiving prophylactic and therapeutic doses over a median 9- and 7-day treatment period, respectively. No patients had thrombotic complications.

CONCLUSION

Tinzaparin PK parameters and profiles were not affected by renal impairment. This suggests that tinzaparin, at therapeutic or prophylactic dose, could be an alternative to unfractionated heparin in hospitalized patients with severe renal impairment.

Smaller nadroparin dose reductions required for patients with renal impairment: A multicenter cohort study

BACKGROUND

Guidelines advise 50 % and 25 % dose reduction of the therapeutic nadroparin dose (86 IU/kg) in patients with eGFR 15-29 and 30-60 ml/min respectively. For monitoring, peak anti-Xa levels are suggested. Data lack whether this results in therapeutic anti-Xa levels or in anti-Xa levels that are comparable to those of patients without renal impairment.

AIMS

To determine dose ranges in patients with renal impairment that result in therapeutic anti-Xa levels and to determine the percentage of the 86 IU/kg dose that results in anti-Xa levels normally occurring in patients without renal impairment.

METHODS

A retrospective cohort study was conducted in five hospitals. Patients ≥18 years of age, with an eGFR ≥ 15 ml/min were included. The first correctly sampled peak (i.e. 3-5 h after ≥ third administration, regardless of dose per patient) was included. Simulated prediction models were developed using multiple linear regression.

RESULTS

770 patients were included. eGFR and hospital affected the association between dose and anti-Xa level. The doses for peak anti-Xa levels of 0.75 IU/ml differed substantially between hospitals and ranged from 55 to 91, 65-359 and 68-168 IU/kg in eGFR 15-29, 30-60 and > 60 ml/min/1.73m2, respectively. In eGFR 15-29 and 30-60 ml/min/1.73m2, doses of 75 % and 91 % of 86 IU/kg respectively, were needed for anti-Xa levels normally occurring in patients with eGFR > 60 ml/min.

CONCLUSION

We advise against anti-Xa based dose-adjustments as long as anti-Xa assays between laboratories are not harmonized and an anti-Xa target range is not validated. A better approach might be to target levels similar to eGFR > 60 ml/min/1.73m2, which are achieved by smaller dose reductions.

Being precise with anticoagulation to reduce adverse drug reactions: are we there yet?

Anticoagulants are potent therapeutics widely used in medical and surgical settings, and the amount spent on anticoagulation is rising. Although warfarin remains a widely prescribed oral anticoagulant, prescriptions of direct oral anticoagulants (DOACs) have increased rapidly. Heparin-based parenteral anticoagulants include both unfractionated and low molecular weight heparins (LMWHs). In clinical practice, anticoagulants are generally well tolerated, although interindividual variability in response is apparent. This variability in anticoagulant response can lead to serious incident thrombosis, haemorrhage and off-target adverse reactions such as heparin-induced thrombocytopaenia (HIT). This review seeks to highlight the genetic, environmental and clinical factors associated with variability in anticoagulant response, and review the current evidence base for tailoring the drug, dose, and/or monitoring decisions to identified patient subgroups to improve anticoagulant safety. Areas that would benefit from further research are also identified. Validated variants in VKORC1, CYP2C9 and CYP4F2 constitute biomarkers for differential warfarin response and genotype-informed warfarin dosing has been shown to reduce adverse clinical events. Polymorphisms in CES1 appear relevant to dabigatran exposure but the genetic studies focusing on clinical outcomes such as bleeding are sparse. The influence of body weight on LMWH response merits further attention, as does the relationship between anti-Xa levels and clinical outcomes. Ultimately, safe and effective anticoagulation requires both a deeper parsing of factors contributing to variable response, and further prospective studies to determine optimal therapeutic strategies in identified higher risk subgroups.

UK prescribing practice of anticoagulants in patients with chronic kidney disease: a nephrology and haematology-based survey

A survey to gain insight into anticoagulant prescribing practice in the setting of chronic kidney disease (CKD) across the UK was disseminated via renal and haematology networks. Areas of anticoagulant use included patients with venous thromboembolism (VTE), requiring thromboprophylaxis for VTE, Atrial Fibrillation (AF) and nephrotic syndrome.An online-survey was disseminated via British Haematology Society, UK Kidney Association, and Renal Pharmacy Group over a five month period. All responses were voluntary and anonymous.Among 117 responses there were 49 nephrology doctors, 47 renal pharmacists and 20 haematology clinicians. A specialist multidisciplinary team to discuss the specific anticoagulant management of these patients was only available to 3% (4/117) respondents. Renal function estimate used for anticoagulant dosing was mainly Cockcroft-Gault for pharmacists and haematology but lab-based estimates were used by nephrology doctors. Therapeutic dose of Low Molecular Weight Heparin was mostly likely to be reduced by one-third when used for VTE treatment, with the majority of units undertaking anti-Xa monitoring in CKD stage 5 and dialysis. Direct-acting Oral Anticoagulants are being used in patients with nephrotic syndrome, those with CKD stage 5 and on dialysis for VTE and AF in the absence of license in these indications.This survey highlighted the significant differences between anticoagulant prescribing in CKD between two professional specialties and marked variation between centres in anticoagulant management strategies employed for these patients. With gaps still existing in the evidence base and answers to these not expected within the next few years, development of a best-practice guideline would be warranted to support clinicians in this field.

A systematic review of the efficacy and safety of anticoagulants in advanced chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) have an increased risk of venous thromboembolism (VTE) and atrial fibrillation (AF). Anticoagulants have not been studied in randomised controlled trials with CrCl < 30 ml/min. The objective of this review was to identify the impact of different anticoagulant strategies in patients with advanced CKD including dialysis.

METHODS

We conducted a systematic review of randomized controlled trials and cohort studies, searching electronic databases from 1946 to 2022. Studies that evaluated both thrombotic and bleeding outcomes with anticoagulant use in CrCl < 50 ml/min were included.

RESULTS

Our initial search yielded 14,503 papers with 53 suitable for inclusion. RCTs comparing direct oral anticoagulants (DOACs) versus warfarin for patients with VTE and CrCl 30-50 ml/min found no difference in recurrent VTE events (RR 0.68(95% CI 0.42-1.11)) with reduced bleeding (RR 0.65 (95% CI 0.45-0.94)). Observational data in haemodialysis suggest lower risk of recurrent VTE and major bleeding with apixaban versus warfarin. Very few studies examining outcomes were available for therapeutic and prophylactic dose low molecular weight heparin for CrCl < 30 ml/min. Findings for patients with AF on dialysis were that warfarin or DOACs had a similar or higher risk of stroke compared to no anticoagulation. For patients with AF and CrCl < 30 ml/min not on dialysis, anticoagulation should be considered on an individual basis, with limited studies suggesting DOACs may have a preferable safety profile.

CONCLUSION

Further studies are still required, some ongoing, in patients with advanced CKD (CrCl < 30 ml/min) to identify the safest and most effective treatment options for VTE and AF.

Trough anti-Xa activity after intermediate dose nadroparin for thrombosis prophylaxis in critically ill patients with COVID-19 and acute kidney injury

Our objective was to assess the incidence of drug bioaccumulation in critically ill COVID-19 patients with AKI receiving intermediate dose nadroparin for thrombosis prophylaxis. We conducted a Prospective cohort study of critically ill COVID-19 patients. In patients on intermediate dose nadroparin (5700 IU once daily) we assessed the incidence of bioaccumulation (trough anti-Xa level > 0.2 IU/mL) stratified according to presence of AKI. We quantified this association using multilevel analyses. To assess robustness of our observations, we explored the association between AKI and anti-Xa activity in patients receiving high dose nadroparin (> 5700 IU). 108 patients received intermediate dose nadroparin, of whom 24 had AKI during 36 anti-Xa measurements. One patient with AKI (4.2% [95%CI 0.1-21%]) and 1 without (1.2% [95%CI 0.03-6.5%]) developed bioaccumulation (p = 0.39). Development of AKI was associated with a mean increase of 0.04 (95%CI 0.02-0.05) IU/ml anti-Xa activity. There was no statistically significant association between anti-Xa activity and AKI in 51 patients on high dose nadroparin. There were four major bleeding events, all in patients on high dose nadroparin. In conclusion, Bioaccumulation of an intermediate dose nadroparin did not occur to a significant extent in critically ill patients with COVID-19 complicated by AKI. Dose adjustment in AKI may be unnecessary.

Gerinnungsdiagnostik im klinischen Alltag – Teil 2

Während bei einer Vitamin-K-Antagonisten-Therapie die Therapieüberwachung (International Normalized Ratio [INR]) obligat ist, gilt dies für direkte orale Antikoagulanzien (DOAK) oder niedermolekulares Heparin (NMH) nur in ausgewählten klinischen Szenarien. Bei DOAK steht die Bestimmung von Tal- und Spitzenspiegeln des Medikaments im Plasma im Vordergrund, bei NMH die Anti-Xa-Aktivität. Der Zeitpunkt der Probenabnahme in Relation zur Einnahme ist für die Bewertung essenziell. Eine neu aufgetretene Thrombozytopenie im Rahmen stationärer Behandlungen ist häufig. Einordnung der Grunderkrankung, Tag des Auftretens sowie Erfassung medikamentöser Einflüsse und ihrer Dynamik ermöglichen oft die Eingrenzung der Ursache. Die Thrombophilietestung nach venöser Thromboembolie wird aufgrund fehlender therapeutischer Konsequenz zunehmend seltener durchgeführt. Ein Antiphospholipidsyndrom darf aber nicht übersehen werden, da sowohl die Therapiedauer als auch die Wahl des Antikoagulans davon abhängen.

Prophylaxis of cancer‑associated venous thromboembolism with low‑molecular‑weight heparin‑tinzaparin: Real world evidence

Thromboprophylaxis, as a preventive measure for cancer-associated thrombosis (CAT), may be beneficial for patients with active cancer and high-risk for thrombosis. The present post hoc analysis include a total of 407 patients enrolled in the Greek Management of Thrombosis study, who received thromboprophylaxis with tinzaparin. The objectives of the present analysis were: i) To obtain sufficient evidence for the administration of prophylaxis in patients with active cancer, irrespective of Khorana risk assessment model score; ii) to identify the selection criteria for both dose and duration of tinzaparin; and iii) to evaluate the efficacy and safety of tinzaparin administered for CAT prophylaxis. The main tumor types for the patients included in the present study were as follows: Lung (25.1%), pancreatic (14.3%), breast (9.1%), stomach (8.4%), colorectal (7.9%) and ovarian (7.6%). Furthermore, metastatic disease was observed in 69.5% of the patients. High thrombotic burden agents (HTBAs) were administered to 66.3% of the patients, and 17.4% received erythropoietin. A total of 43.7% of the patients exhibited a Khorana score <2. The results of the present study demonstrated that both the presence of metastatic disease and the use of HTBAs seemed to influence oncologists' decisions for the use of thromboprophylaxis in patients with active cancer, regardless of Khorana score. Tinzaparin, in dose expressed in the standard notation for heparins, i.e., anti-Xa factor international units (Anti-Xa IU), was administered at an intermediate dose (InterD; 8,000-12,000 Anti-Xa IU; once daily) to 52.4% of patients, while the remaining patients received a prophylactic dose (ProD; ≤4,500 Anti-Xa IU; once daily). The average duration of thromoprophylaxis was 5 months. Furthermore, a total of 14 (3.4%) thrombotic events and 6 (1.5%) minor bleeding events were recorded. A total of four thrombotic events were observed following an InterD treatment of tinzaparin, while 10 thrombotic events were observed following ProD treatment. The present study also demonstrated that an InterD of tinzaparin was administered more frequently to patients with a body mass index >30 kg/m², a history of smoking and a history of metastatic disease, along with administration of erythropoietin. InterD tinzaparin treatment was found to be potentially more efficacious and without safety concerns. The present study is a registered clinical trial (ClinicalTrials.gov code, NCT03292107; registration date, September 25, 2017).

Venous Thromboembolism In Cancer Patients: "From Evidence to Care"

This article seeks to review the current status of treatment and prevention of venous thromboembolic disease (VTE) in cancer patients after the addition of direct oral anticoagulants (DOAC) to the therapeutic arsenal available. The suitability of DOAC use in complex clinical situations, poorly represented in clinical trials, is controversial and difficult for care activity, making the recommendations in clinical practice guidelines the focus of special attention in this area. Recently, several randomized trials have compared low molecular weight heparin (LMWH) to DOAC for the management of CAT. Potential drug interactions with DOACs or the increased risk of bleeding in intraluminal tumors require special precautions, as do metastatic or primary brain disease and comorbid conditions, such as renal or liver failure, which are not suitably represented in pivotal studies. Furthermore, few data are available for situations involving elevated bleeding risk, with thrombocytopenia levels below the inclusion criterion of clinical trials, or recurrence during active anticoagulant therapy. Similarly, it is less clear that patients and physicians accept the presumption that oral DOAC administration is more convenient than subcutaneous LMWH, particularly when drug absorption may be compromised. The non-inclusion or under-representation of patients at higher risk for complications with anticoagulation in randomized clinical trials, makes their use complex in certain situations in health care. This paper provides a practical review of current clinical guideline recommendations regarding LMWH and/ or DOAC to treat and prevent CAT, as well as the most controversial clinical conditions for their use.

Effects of dalteparin on anti-Xa activities cannot be predicted in critically ill COVID-19 patients

Critically ill COVID‐19 patients are at high risk of thromboembolic events despite routine‐dosed low‐molecular‐weight heparin thromboprophylaxis. However, in recent randomized trials increased‐intensity thromboprophylaxis seemed futile and possibly even harmful. In this explorative pharmacokinetic (PK) study we measured anti‐Xa activities on frequent timepoints in 15 critically ill COVID‐19 patients receiving dalteparin and performed PK analysis by nonlinear mixed‐effect modelling. A linear one‐compartment model with first‐order kinetics provided a good fit. However, wide interindividual variation in dalteparin absorption (variance 78%) and clearance (variance 34%) was observed, unexplained by routine clinical covariates. Using the final PK model for Monte Carlo simulations, we predicted increased‐intensity dalteparin to result in anti‐Xa activities well over prophylactic targets (0.2‐0.4 IU/mL) in the majority of patients. Therapeutic‐intensity dalteparin results in supratherapeutic anti‐Xa levels (target 0.6‐1.0 IU/mL) in 19% of patients and subtherapeutic levels in 22%. Therefore, anti‐Xa measurements should guide high‐intensity dalteparin in critically ill COVID‐19 patients.

Reversal Activity and Toxicity of Heparin-Binding Copolymer after Subcutaneous Administration of Enoxaparin in Mice

Uncontrolled bleeding after enoxaparin (ENX) is rare but may be life-threatening. The only registered antidote for ENX, protamine sulfate (PS), has 60% efficacy and can cause severe adverse side effects. We developed a diblock copolymer, heparin-binding copolymer (HBC), that reverses intravenously administered heparins. Here, we focused on the HBC inhibitory activity against subcutaneously administered ENX in healthy mice. BALB/c mice were subcutaneously injected with ENX at the dose of 5 mg/kg. After 110 min, vehicle, HBC (6.25 and 12.5 mg/kg), or PS (5 and 10 mg/kg) were administered into the tail vein. The blood was collected after 3, 10, 60, 120, 360, and 600 min after vehicle, HBC, or PS administration. The activities of antifactors Xa and IIa and biochemical parameters were measured. The main organs were collected for histological analysis. HBC at the lower dose reversed the effect of ENX on antifactor Xa activity for 10 min after antidote administration, whereas at the higher dose, HBC reversed the effect on antifactor Xa activity throughout the course of the experiment. Both doses of HBC completely reversed the effect of ENX on antifactor IIa activity. PS did not reverse antifactor Xa activity and partially reversed antifactor IIa activity. HBC modulated biochemical parameters. Histopathological analysis showed changes in the liver, lungs, and spleen of mice treated with HBC and in the lungs and heart of mice treated with PS. HBC administered in an appropriate dose might be an efficient substitute for PS to reverse significantly increased anticoagulant activity that may be connected with major bleeding in patients receiving ENX subcutaneously.

Incidence, risk factors, and management of bleeding in patients receiving anticoagulants for the treatment of cancer-associated thrombosis

Updated clinical practice guidelines recommend the long-term use of low-molecular-weight heparins or direct oral anticoagulants as the preferred option for the treatment of cancer-associated thrombosis (CAT), using a personalized approach matching the right drug to the right patient. In most cases, the benefit of anticoagulant therapy outweighs the risk. However, the long-term use of anticoagulants is associated with a non-negligible risk of bleeding, which constitutes a rare but serious adverse effect. Bleeding complications have been reported to be overall 2 to 3 times more frequent in cancer patients with CAT receiving anticoagulation than in non-cancer patients, with a reported incidence of major bleeding ranging from 2.4 to 16.0% in randomized controlled trials (RCT). In the absence of validated risk assessment model to predict the risk of bleeding in these patients, a careful evaluation of each individual profile, with adequate selection of the most appropriate anticoagulant for each individual patient, is warranted for overcoming management challenges, taking in account the numerous factors which may potentiate the overall bleeding risk in these complex patients, such as advanced or metastatic disease, older age, anemia, thrombocytopenia, renal impairment, liver dysfunction, and concomitant anticancer therapies. The purpose of this review is to call for awareness on bleeding complications as a major safety issue of CAT treatment and to summarize data from recent RCT and real-world studies on the incidence and risk factors for bleeding in this unique and challenging population to further help clinicians in decision-making.

Monitoring of Enoxaparin during Hemodialysis Covered by Regional Citrate Anticoagulation in Acute Kidney Injury: A Prospective Cohort Study

Background: Current guidelines recommend the monitoring of anti-factor Xa (anti-Xa) levels to avoid an accumulation of low-molecular-weight heparins in patients with acute kidney injury, but there is no evidence on how to proceed with such monitoring during continuous renal replacement therapy. Against this background, we investigated the potential accumulation of enoxaparin administered subcutaneously for venous thromboembolism prophylaxis in critically ill patients during continuous renal replacement therapy covered by regional citrate anticoagulation. Methods: Anti-Xa levels were measured at baseline (≤12 h before renal replacement therapy) and on three consecutive days (A to C) when enoxaparin had reached trough levels. Supplementary testing included modified assays of rotational thromboelastometry known to be highly sensitive for low-molecular-weight heparins. Results: The 16 men and 13 women included were adults comparable in age, body mass index, thromboembolism risk assessment, and clinical severity of the disease. Throughout the four examinations, the median trough levels of anti-Xa remained below the detection limit of the test (<0.1 IU mL⁻¹), with interquartile ranges of <0.1 to 0.14 IU mL⁻¹ at baseline and <0.1 to 0.16 IU mL⁻¹ on days A/B/C. All rotational thromboelastometry parameters of clot initiation and clot formation dynamics did not significantly change from baseline to day C. Conclusions: Neither anti-Xa levels nor modified assays of rotational thromboelastometry revealed any accumulation of enoxaparin administered for thromboprophylaxis during continuous renal replacement therapy covered by regional citrate anticoagulation. Although generally recommended in patients with acute kidney injury, monitoring of anti-Xa levels should be questioned in this defined setting.

Heparin beyond anti-coagulation

Heparin has served as a mainstream anticoagulant for over eight decades. Clinically heparin-derived compounds significantly contribute to prevention and treatment of thrombotic events complicated in numerous medical conditions such as venous thromboembolism, coronary artery disease and extracorporeal circulation processes. Moreover in recent years, various off-labeled efficacious potentials of heparin beyond anti-coagulation are dramatically emerging, and increasingly investigated in clinical studies. Herein this article presents a comprehensive update on the expanded applications of heparin agents, covering the pregnant clinic, respiratory inflammation, renal disease, sepsis, pancreatitis, among others. It aims to maximize the beneficial profile of a pharmaceutical product through medical re-purposing development, exemplified by heparin, to address the unmet clinical needs of severe illness including coronavirus disease 2019 (COVID-19).

Optimization of Heparin Monitoring with Anti-FXa Assays and the Impact of Dextran Sulfate for Measuring All Drug Activity

Heparins, unfractionated or low molecular weight, are permanently in the spotlight of both clinical indications and laboratory monitoring. An accurate drug dosage is necessary for an efficient and safe therapy. The one-stage kinetic anti-FXa assays are the most widely and universally used with full automation for large series, without needing exogenous antithrombin. The WHO International Standards are available for UFH and LMWH, but external quality assessment surveys still report a high inter-assay variability. This heterogeneity results from the following: assay formulation, designed without or with dextran sulfate to measure all heparin in blood circulation; calibrators for testing UFH or LMWH with the same curve; and automation parameters. In this study, various factors which impact heparin measurements are reviewed, and we share our experience to optimize assays for testing all heparin anticoagulant activities in plasma. Evidence is provided on the usefulness of low molecular weight dextran sulfate to completely mobilize all of the drug present in blood circulation. Other key factors concern the adjustment of assay conditions to obtain fully superimposable calibration curves for UFH and LMWH, calibrators' formulations, and automation parameters. In this study, we illustrate the performances of different anti-FXa assays used for testing heparin on UFH or LMWH treated patients' plasmas and obtained using citrate or CTAD anticoagulants. Comparable results are obtained only when the CTAD anticoagulant is used. Using citrate as an anticoagulant, UFH is underestimated in the absence of dextran sulfate. Heparin calibrators, adjustment of automation parameters, and data treatment contribute to other smaller differences.

Heparins have adequate ex vivo anticoagulant effects in hospitalized patients with cirrhosis

BACKGROUND

Patients with cirrhosis are at risk of venous thromboembolism (VTE), but strategies for thromboprophylaxis have not been defined. Previous in vitro studies suggest an altered anticoagulant effect of heparins in patients with cirrhosis.

OBJECTIVES

To assess the anticoagulant effects of prophylactic low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH) doses in patients with cirrhosis in a real-life clinical setting.

METHODS

We studied patients with cirrhosis (n = 16) and acute-on-chronic liver failure (ACLF) (n = 14), and compared these with patients without underlying liver disease admitted to non-liver general medical wards (n = 18) and non-liver intensive care units (n = 14), respectively. Blood samples were taken before and 4 h after administration of the first dose of LMWH or UFH. We assessed hemostatic status using thrombin generation assays, thrombin-antithrombin complexes (TAT), and conventional coagulation assays, and included healthy controls (n = 20) to establish reference values. Anti-Xa activity was determined to estimate peak heparin levels.

RESULTS

Baseline thrombin generation was similar among all cohorts and healthy controls despite alterations in conventional coagulation assays. On heparin, both absolute and proportional changes of thrombin generation were comparable between all four cohorts (-62% to -85%). TAT levels decreased in all cohorts apart from the ACLF cohort, but did not correlate with the proportional change in thrombin generation. Anti-Xa activity correlated with the proportional change in thrombin generation in patients receiving LMWH, but not in patients receiving UFH.

CONCLUSIONS

These data suggest that current prophylactic heparin doses have comparable anticoagulant effects in patients with cirrhosis compared with patients without underlying liver disease.

Techniques for Detection of Clinical Used Heparins

Heparins and sulfated polysaccharides have been recognized as effective clinical anticoagulants for several decades. Heparins exhibit heterogeneity depending on the sources. Meanwhile, the adverse effect in the clinical uses and the adulteration of oversulfated chondroitin sulfate (OSCS) in heparins develop additional attention to analyze the purity of heparins. This review starts with the description of the classification, anticoagulant mechanism, clinical application of heparins and focuses on the existing methods of heparin analysis and detection including traditional detection methods, as well as new methods using fluorescence or gold nanomaterials as probes. The in-depth understanding of these techniques for the analysis of heparins will lay a foundation for the further development of novel methods for the detection of heparins.

Anti-Xa levels in critically ill children receiving enoxaparin for venothromboembolism prophylaxis

Venothrombolism (VTE) prophylaxis is increasingly utilized in pediatric intensive care units (PICUs). Enoxaparin, a low-molecular weight heparin, is frequently used for this purpose. Enoxaparin can also be used for therapeutic anticoagulation in cases of known thrombus. In such cases, monitoring involves obtaining serum anti- Xa levels with a target value of 0.5-1 units/mL. No monitoring recommendations currently exist for enoxaparin when intended for pediatric VTE prophylaxis. We hypothesize that a clinically important number of patients on VTE prophylaxis with enoxaparin have serum anti-Xa levels consistent with values targeted for therapeutic anticoagulation. We found that over 20% of patients on VTE prophylaxis with enoxaparin had serum anti-Xa levels consistent with true therapeutic anticoagulation (anti-Xa level 0.5-1 units/mL) during their enoxaparin course and 5% achieved values of supratherapeutic anticoagulation (anti-Xa level >1 units/mL). Serum anti-Xa level did not correlate with once versus twice daily dosing, body mass index (BMI), or creatinine level. Blood urea nitrogen (BUN) was found to have a positive odds ratio for an anti-Xa level ≥ 0.5 units/mL. We believe that this incidence of unintended therapeutic anticoagulation indicates a clinically significant number and therefore routine anti-Xa evaluation while on VTE prophylaxis is warranted within our population.

Tinzaparin Safety in Patients With Cancer and Renal Impairment: A Systematic Review

Low-molecular-weight heparins are approved for primary and secondary venous thromboembolism prevention. Tinzaparin is the low-molecular-weight heparin with the highest average molecular weight. The purpose of this systematic review is to provide an update regarding the safety profile of tinzaparin, prescribed either as a prophylactic or as a therapeutic regimen for venous thromboembolism in special populations, including cancer patients and patients with renal impairment. We identified prospective studies up to August 2020 reporting safety outcomes for cancer patients and patients with renal impairment on tinzaparin regimens. In patients with cancer major bleeding rates fluctuated between 0.8% and 7%. Patients on tinzaparin exhibited significantly lower rates of clinically relevant nonmajor bleeding events in comparison with those on vitamin K antagonists. Bioaccumulation of tinzaparin was not correlated with age, body weight or creatinine clearance. Periodic administration of either prophylactic or therapeutic doses of tinzaparin did not result in bioaccumulation, even in patients with severe renal impairment and creatinine clearance < 20 ml/min. Major bleeding rates for non-cancer patients with renal impairment on prophylactic tinzaparin regimens were 0%. Non-cancer patients with renal impairment on therapeutic tinzaparin regimens exhibited major bleeding in 0 to 3.4% of cases; major bleeding rates were higher for cancer patients with renal impairment on therapeutic tinzaparin regimens (4.3 to 10%). Tinzaparin can be used without dose adjustment in patients with severe renal impairment and creatinine clearance > 20 ml/min. Tinzaparin represents a safe choice for special populations at increased risk for thrombosis and bleeding.

A Distinctive Approach to Venous Thromboembolism Treatment in a Pediatric, Hemodialysis Patient: A Case Report

Enoxaparin is a low molecular weight heparin (LMWH) that is the mainstay for treatment of pediatric patients with a venous thromboembolism, which provides better compliance compared with the use of unfractionated heparin (UFH) in long-term anticoagulation. Although data are limited in pediatric patients with renal insufficiency, enoxaparin can be used in this population. Data related to its use in hemodialysis (HD) pediatric patients is almost non-existent. A major concern for enoxaparin use in patients with renal insufficiency or for those on HD is bleeding. A few studies in adults showed an increased risk of bleeding, but the risk was similar to that of UFH when the two were compared. This case report describes the use of enoxaparin in an 8-year-old female who is on hemodialysis, without any bleeding or clotting complications. Although systematic trials are needed to support the safety and efficacy of LMWH in pediatric patients with renal dysfunction or on HD, this case will provide limited information for enoxaparin use in this population.

Guidance for the Management of Patients with Vascular Disease or Cardiovascular Risk Factors and COVID-19: Position Paper from VAS-European Independent Foundation in Angiology/Vascular Medicine

COVID-19 is also manifested with hypercoagulability, pulmonary intravascular coagulation, microangiopathy, and venous thromboembolism (VTE) or arterial thrombosis. Predisposing risk factors to severe COVID-19 are male sex, underlying cardiovascular disease, or cardiovascular risk factors including noncontrolled diabetes mellitus or arterial hypertension, obesity, and advanced age. The VAS-European Independent Foundation in Angiology/Vascular Medicine draws attention to patients with vascular disease (VD) and presents an integral strategy for the management of patients with VD or cardiovascular risk factors (VD-CVR) and COVID-19. VAS recommends (1) a COVID-19-oriented primary health care network for patients with VD-CVR for identification of patients with VD-CVR in the community and patients' education for disease symptoms, use of eHealth technology, adherence to the antithrombotic and vascular regulating treatments, and (2) close medical follow-up for efficacious control of VD progression and prompt application of physical and social distancing measures in case of new epidemic waves. For patients with VD-CVR who receive home treatment for COVID-19, VAS recommends assessment for (1) disease worsening risk and prioritized hospitalization of those at high risk and (2) VTE risk assessment and thromboprophylaxis with rivaroxaban, betrixaban, or low-molecular-weight heparin (LMWH) for those at high risk. For hospitalized patients with VD-CVR and COVID-19, VAS recommends (1) routine thromboprophylaxis with weight-adjusted intermediate doses of LMWH (unless contraindication); (2) LMWH as the drug of choice over unfractionated heparin or direct oral anticoagulants for the treatment of VTE or hypercoagulability; (3) careful evaluation of the risk for disease worsening and prompt application of targeted antiviral or convalescence treatments; (4) monitoring of D-dimer for optimization of the antithrombotic treatment; and (5) evaluation of the risk of VTE before hospital discharge using the IMPROVE-D-dimer score and prolonged post-discharge thromboprophylaxis with rivaroxaban, betrixaban, or LMWH.

Dosage reduction of low weight heparin in patients with renal dysfunction: Effects on anti-Xa levels and clinical outcomes

Background

To prevent bio-accumulation of low molecular weight heparins (LMWHs) in patients with decreased kidney function, dosage reduction and anti-Xa monitoring has been suggested. The aim of this study was to investigate the effect of pre-emptive dosage reduction of LMWH on anti-Xa levels. Furthermore, we investigated the association between anti-Xa levels and bleeding, thrombotic events and mortality.

Methods

In this single center study, we followed 499 patients with decreased renal function in whom anti-Xa levels were measured. We observed how many patients had anti-Xa levels that fell within the reference range, with a standard protocol of a pre-emptive dosage reduction of LMWH (25% reduction in patients with an estimated glomerular filtration rate (eGFR) between 30 and 60 ml/min/1.73m² and a reduction of 50% in patients with an eGFR below the 30 ml/min/1.73m²). Furthermore, Cox proportional hazard analyses were used to estimate hazard ratios to investigate the association between anti-Xa levels and major bleeding, thrombotic events and mortality within three months of follow-up.

Results

In a cohort of 499 patients (445 dalteparin and 54 nadroparin users), a pre-emptive dosage reduction of LMWH led to adequate levels of anti-Xa in only 19% of the patients (12% for the dalteparin users and 50% for nadroparin users). We did not find an association between anti-Xa levels and bleeding, thrombosis or mortality.

Conclusion

Pre-emptive dosage reduction of LMWH leads to low anti-Xa levels in a large proportion, but this was not associated with bleeding, thrombosis or mortality.

Haemorrhagic complications in patients with renal insufficiency during treatment or prophylaxis with dalteparin

OBJECTIVES

Low-molecular-weight heparins are widely used in clinical practice for the treatment or prophylaxis of venous thromboembolism (VTE). As these drugs are eliminated mainly by renal means, any renal function impairment may lead to higher plasma concentrations and increase the risk of bleeding. This study aims to evaluate whether in clinical practice there is an increase in the occurrence of bleeding in patients with renal insufficiency (RI) during treatment or prophylaxis with dalteparin, and to analyse the risk factors potentially influencing the appearance of such bleeding events.

METHODS

Patients were sampled from the Universitary Severo Ochoa Hospital, Leganés, Spain. This was a retrospective cohort study with a 1 year inclusion period, conducted at a Spanish university hospital with 400 beds, on patients undergoing treatment or prophylaxis for VTE with dalteparin for a minimum of 3 days. The main outcome measure was the number of patients who had bleeding events, independently of their severity, during dalteparin administration in patients with RI.

RESULTS

367 patients were included in the study. Bleeding occurred in 17.9% of patients in the group with RI and in 7.3% of patients with normal renal function (NRF). Most haemorrhages in both cohorts were grade 2 on the WHO scale (64.7% in the RI group and 69.2% in the NRF group). Logistic regression analysis allowed the presence of RI (MDRD-4 (Modification of Diet in Renal Disease) <50 mL/min) to be identified as a risk factor.

CONCLUSION

Patients with RI treated with dalteparin face a higher risk of bleeding than those with NRF, which seems to make it necessary to monitor and seek new dosage adjustments for these patients.Impact on practice statements: This study yields new data on dalteparin in RI, which has not been widely studied before.

Plasma levels of enoxaparin oligosaccharides, antifactor-Xa and thrombin generation in patients undergoing haemodialysis

: Low molecular weight heparins are used during haemodialysis for thromboprophylaxis of the dialysis circuit, with plasma antifactor-Xa (anti-Xa) activity used as a surrogate measure for effective anticoagulation. However, this pharmacokinetic parameter does not always correlate with pharmacodynamic effects in patients. The aim of this study was to investigate the relationship between actual plasma levels of the low molecular weight heparins enoxaparin, anti-Xa activity, and global coagulation measurement of thrombin generation during haemodialysis. Blood was analysed from 16 adult patients with end-stage kidney disease at 0, 2, 4 h, and at completion of 31 dialysis sessions where single fixed doses of 20 (n = 3), 40 (n = 16), 60 (n = 6), or 80 (n = 6) mg of enoxaparin (equating to 0.23-1.07 mg/kg) were used as thromboprophylaxis. Plasma enoxaparin oligosaccharides [degree of polymerization (dp)6-dp16] were measured by high-performance size exclusion chromatography, anti-Xa activity by colourimetric assay, and thrombin generation by calibrated automated thrombogram. Plasma enoxaparin fragments were undetectable at the beginning of each dialysis, peaked at 2 h to levels that correlated with dose (r = 0.68, P < 0.001) then remained relatively stable. In contrast, therapeutic anti-Xa levels achieved at 2 h in 18 cases (58%) quickly dropped to only six cases (19%) at the end of dialysis, by which time thrombin generation had also recovered in 81% of patients. Statistical modelling revealed a threshold value of anti-Xa at 0.53 IU/ml that supressed thrombin generation to 15.28% of baseline (P < 0.001). Despite loss of anticoagulant activity in the majority of patients, plasma levels of enoxaparin oligosaccharides remained detectable and relatively unchanged throughout dialysis.

Evaluation of prophylactic dosages of Enoxaparin in non-surgical elderly patients with renal impairment

Background

Thromboprophylaxis dosing strategies using enoxaparin in elderly patients with renal disease are limited, while dose adjustments or monitoring of anti-Xa levels are recommended. We sought to evaluate the efficacy and safety of enoxaparin 20 mg versus 30 mg subcutaneously daily by comparing anti-Xa levels, thrombosis and bleeding.

Methods

We conducted a prospective, single-blinded, single-center randomized clinical trial including non-surgical patients, 70 years of age or older, with renal disease requiring thromboprophylaxis. Patients were randomized to receive either 20 mg or 30 mg of enoxaparin. The primary endpoint was peak anti-Xa levels on day 3. Secondary endpoints included trough anti-Xa levels on day 3, achievement of within range prophylactic target peak anti-Xa levels and the occurrence of hemorrhage, thrombosis, thrombocytopenia or hyperkalemia during hospitalization.

Results

Thirty-two patients were recruited and sixteen patients were randomized to each arm. Mean peak anti-Xa level was significantly higher in 30 mg arm (n = 13) compared to the 20 mg arm (n = 11) 0.26 ± 0.11, 95%CI (0.18–0.34), versus 0.14 ± 0.09, 95CI (0.08–0.19) UI/ml, respectively; p = 0.004. Mean trough anti-Xa level was higher in 30 mg arm (n = 10) compared to the 20 mg arm (n = 16), 0.06 ± 0.03, 95CI (0.04–0.08) versus 0.03 ± 0.03, 95CI (0.01–0.05) UI/ml, respectively; p = 0.044. Bleeding events reported in the 30 mg arm were one retroperitoneal bleed requiring multiple transfusions, and in the 20 mg arm one hematuria. No thrombotic events were reported.

Conclusion

Peak anti-Xa levels provided by enoxaparin 20 mg were lower than the desired range for thromboprophylaxis in comparison to enoxaparin 30 mg.

Trial registration

The trial was retrospectively registered on ClinicalTrials.gov identifier: NCT03158792. Registered: May 18, 2017.

Evaluation of unmet clinical needs in prophylaxis and treatment of venous thromboembolism in high-risk patient groups: cancer and critically ill

Background

Clinical practice shows that venous thromboembolism (VTE) presents a substantial burden in medical patients, and awareness and advocacy for its primary and secondary prevention remains inadequate. Specific patient populations, such as those with cancer and the critically ill, show elevated risk for VTE, bleeding or both, and significant gaps in VTE prophylaxis and treatment exist in these groups.

Objective

To present novel insights and consolidated evidence collected from experts, clinical practice guidelines and original studies on the unmet needs in thromboprophylaxis, and on the treatment of VTE in two high-risk patient groups: patients with cancer and the critically ill.

Methodology

To identify specific unmet needs in the management of VTE, a methodology was designed and implemented that assessed gaps in prophylaxis and treatment of VTE through interviews with 44 experts in the field of thrombosis and haemostasis, and through a review of current guidelines and seminal studies to substantiate the insights provided by the experts. The research findings were then analysed, discussed and consolidated by a multidisciplinary group of experts.

Results

The gap analysis methodology identified shortcomings in the VTE risk assessment tools, patient stratification approaches for prophylaxis, and the suboptimal use of anticoagulants for primary prophylaxis and treatment.

Conclusions

Specifically, patients with cancer need better VTE risk assessment tools to tailor primary thromboprophylaxis to tumour types and disease stages, and the potential for drug–drug interactions needs to be considered. In critically ill patients, unfractionated heparin is not advised as a first-line treatment option, and the strength of evidence is increasing for direct oral anticoagulants as a treatment option over low-molecular-weight heparins.

Electronic supplementary material

The online version of this article (10.1186/s12959-019-0196-6) contains supplementary material, which is available to authorized users.

An in vitro study to investigate the interference of enoxaparin on plasma levels of direct oral factor Xa inhibitors measured by chromogenic assays

INTRODUCTION

Co-administration of enoxaparin and a direct oral factor Xa inhibitor (xabans: apixaban, edoxaban, rivaroxaban) could give rise to the problem of overlapping the anti-Xa activity when measuring direct oral anticoagulant (DOAC) levels. We aimed to evaluate in vitro the degree of the interference of increasing enoxaparin concentrations on xaban plasma levels measured by different chromogenic anti-Xa assays with drug-specific calibrators and controls.

METHODS

Seven plasma samples were spiked with apixaban, edoxaban, or rivaroxaban at fixed concentration, and enoxaparin at increasing concentrations (0, 0.125, 0.250, 0.50, 1.0, 1.50, and 2.0 IU/mL). The evaluated chromogenic assays were as follows: Biophen DiXaI and Biophen Heparin LRT (Hyphen BioMed), Berichrom Heparin and Innovance Heparin (Siemens), STA-Liquid Anti-Xa (Stago Diagnostics), Technochrom anti-Xa (Technoclone), and HemosIL Liquid Anti-Xa (Werfen).

RESULTS

The presence of enoxaparin caused increased DOAC levels, with over-estimation depending on the anti-Xa assay and on the heparin concentration in the sample. The smallest over-estimation was in the sample with enoxaparin 0.125 IU/mL and the greatest in the sample with enoxaparin 2.0 IU/mL (0%, 3.1%, and 7.4% vs 583.8%, 526.1%, and 415.2% for apixaban, edoxaban, and rivaroxaban, respectively). Biophen DiXaI showed lower interference compared to other methods (maximum over-estimation in the presence of enoxaparin 2.0 IU/mL: 56.4% dosing rivaroxaban by Biophen DIXaI vs 583.8% dosing apixaban by Berichrom Heparin).

CONCLUSION

The presence of enoxaparin interferes with xabans measurement by chromogenic anti-Xa assays causing falsely elevated DOAC levels, the over-estimation being dependent on the anti-Xa assay and on the heparin concentration in the sample.

Improving the adoption of optimal venous thromboembolism prophylaxis in critically ill patients: A process evaluation of a complex quality improvement initiative

PURPOSE

This study evaluated a complex initiative to increase evidence-based use of low molecular weight heparin for venous thromboembolism prophylaxis among adult medical-surgical ICU patients.

MATERIALS AND METHODS

This study included: quantitative survey and interviews. Participants were healthcare providers within four ICUs. Surveys collected knowledge of evidence underpinning best practice, exposure to the implementation strategies and their perceived utility, and recommendations. The interview expanded on survey topics. Descriptive statistics summarized the data and chi-squared tests were used to compare groups. Qualitative data were analyzed using a blended deductive and inductive coding approach.

RESULTS

Providers had good knowledge of the evidence (range = 58% to 94%). Pharmacist-to-physician reminders (80%), other reminders (50%), and local guidelines (50%) were the most commonly observed strategies. Local champions (76%), on-site education (74%), and computerized decision support system (69%) were perceived to be most helpful. Interviews elicited five themes: provider roles, perceptions of the implementation strategies, facilitators and barriers to uptake of best practice, and recommendations. Assessment of the implementation strategies varied by professional group.

CONCLUSIONS

The findings of this process evaluation identified implementation strategies that can improve the use of evidence-informed practices, help interpret outcomes in the context of interventions and guide future quality improvement initiatives.

Enoxaparin 20 mg for thromboprophylaxis in severe renal impairment

Objective

This study was performed to evaluate the efficacy of daily subcutaneous enoxaparin 20 mg in patients with renal failure.

Methods

This retrospective cohort study included nonsurgical patients aged ≥18 years with a creatinine clearance rate of <30 mL/minute who were prescribed enoxaparin 20 mg subcutaneously (SC) daily for ≥3 days. The main outcome measures were the occurrence of a venous thromboembolic event (VTE) and bleeding events.

Results

One hundred sixty patients were identified. VTE occurred in 9 patients (5.6%), and bleeding events occurred in 37 (23.1%). Multivariable analysis showed that an age of >75 years was significantly associated with an increased risk of bleeding, while a creatinine clearance rate of 15 to 29 mL/minute was significantly associated with a lower risk of bleeding.

Conclusion

In patients with renal failure, enoxaparin 20 mg SC daily resulted in a 5.6% incidence of VTE, which is similar to the previously published acceptable incidence of VTE in patients with normal renal function receiving enoxaparin 40 mg SC daily. The incidence of major bleeding events was 10%, which is lower than that previously published in the literature.

Anticoagulants in frail patients. Seven situations at risk

In the case of venous thromboembolic disease (VTE), physicians are facing more and more difficulties in managing VTE and their treatment in frail patients. These patients could present several risk situations such as: chronic kidney disease (CKD), underweight or malnourished, falls, cognitive impairment, multi-medicated patients, cancer and pregnancy. Guidelines typically recommend anticoagulation. There are multiple challenges in the safe use of anticoagulation in frail patients, including bleeding risk, monitoring and adherence, and polypharmacy. The objective of this review is to explore these at-risk situations and to suggest adequate anticoagulation therapy, when possible, in each of these complex situations.

Extended Venous Thromboembolism Prophylaxis after Radical Cystectomy: A Call for Adherence to Current Guidelines

PURPOSE

Radical cystectomy is inherently associated with morbidity. We assess the timing and incidence of venous thromboembolism, review current guideline recommendations and provide evidence for considering extended venous thromboembolism prophylaxis in all patients undergoing radical cystectomy.

MATERIALS AND METHODS

We searched PubMed® for available literature on radical cystectomy and venous thromboembolism, focusing on incidence and timing, evidence supporting extended venous thromboembolism prophylaxis in patients undergoing radical cystectomy or abdominal oncologic surgery, current guideline recommendations, safety considerations and direct oral anticoagulants. Search terms included "radical cystectomy," "venous thromboembolism," "prophylaxis," and "extended oral anticoagulants" and "direct oral anticoagulants" alone and in combination. Relevant articles were reviewed, including original research, reviews and clinical guidelines. References from review articles and guidelines were also assessed to develop a narrative review.

RESULTS

The incidence of symptomatic venous thromboembolism in short-term followup after radical cystectomy is 3% to 11.6%, of which more than 50% of cases will occur after hospital discharge. Meta-analyses of clinical trials in patients undergoing major abdominal oncologic operations suggest a decreased risk of venous thromboembolisms for patients receiving extended (4 weeks) venous thromboembolism prophylaxis. Extended prophylaxis should be considered in all radical cystectomy cases. Although the relative risk of bleeding also increases, the overall net benefit of extended prophylaxis clearly favors use for at least 28 days postoperatively. Extrarenal eliminated prophylaxis agents are preferred given the risk of renal insufficiency in radical cystectomy cases, with newer oral anticoagulants providing an alternative route of administration.

CONCLUSIONS

Patients undergoing radical cystectomy are at high risk for venous thromboembolism after hospital discharge. There is strong evidence that extended prophylaxis significantly decreases the risk of venous thromboembolism in oncologic surgery cases. Use of extended prophylaxis after radical cystectomy has been poorly adopted, emphasizing the need for better adherence to current urology procedure specific guidelines as extended prophylaxis for radical cystectomy is the standard of care. Specific and rare circumstances may require case by case assessment.

The Role of Tinzaparin in Oncology

Current guidelines recommend low-molecular-weight heparin treatment in patients with cancer with established venous thromboembolism (VTE). The aim of this article was to study the pharmacological properties and effectiveness of tinzaparin in patients with cancer as well as its potential anticancer properties. A search of PubMed and ScienceDirect databases up to March 2016 was carried out to identify published studies that detect the properties and use of tinzaparin in oncology. Protamine sulfate partially (60% to 65%) neutralized tinzaparin’s anti-Xa activity. No dose adjustment of tinzaparin is needed even in patients with severe renal impairment and Creatinine Clearance ≥20 mL/min. Tinzaparin demonstrated a statistically significant decline in VTE recurrence at 1 year post the index thromboembolic event. A statistically significant reduction in minor bleeding rates was also described, whereas major bleeding events did not decrease in patients with cancer treated with tinzaparin versus those who received vitamin K antagonists. Tinzaparin treatment in patients suffering from deep vein thrombosis reduced the incidence of postthrombotic syndrome and venous ulcers. Tinzaparin’s ability to prevent both metastatic dissemination of cancer cells and tumor angiogenesis has been delineated in preclinical research. Current data show that tinzaparin is safe and efficacious either for short-term or for long-term treatment of VTE in patients with cancer. Clinical trials are needed in order to examine the utility of tinzaparin in primary prevention of VTE and validate its potential anticancer advantages exhibited in preclinical research.

Phase I Study of Dalteparin in Combination With Sunitinib in Patients With Metastatic Clear Cell Renal Carcinoma

BACKGROUND

Based on the tumor-driven concomitant activation of angiogenesis and coagulation we conducted a phase I combination study of sunitinib with the low molecular weight heparin dalteparin in patients with metastatic clear cell renal cell carcinoma (ccRCC).

MATERIALS AND METHODS

Patients received standard treatment with sunitinib (50 mg daily, 4 weeks on, 2 weeks off). During the second week of no sunitinib in the first cycle (week 6) patients received dalteparin monotherapy (in escalating doses). Combination therapy of the 2 agents was administered from the second cycle onward. Seventeen patients were enrolled at 3 dose levels of dalteparin.

RESULTS

Diarrhea and fatigue were the most frequent reported drug-related toxicities (41%). One dose-limiting toxicity (grade 3 anemia) was observed at the highest dose level of dalteparin. There were 4 partial responses (24%) and the median progression-free survival in this study was 14 months (95% confidence interval, 8.0-23.4). Anti-factor Xa levels were increased during combination therapy compared with dalteparin monotherapy.

CONCLUSIONS

Combination therapy of sunitinib with therapeutic doses of dalteparin is safe and well tolerated. The increased anti-factor Xa levels during combination treatment suggest that sunitinib might increase the anticoagulation activity of dalteparin. The positive safety profile warrants prospective evaluation of the clinical benefit of this combination strategy in patients with ccRCC.