For the initial treatment of venous thromboembolism: are all low-molecular-weight heparin compounds the same?

Once versus twice daily low molecular weight heparin for the initial treatment of venous thromboembolism

BACKGROUND

In the initial treatment of venous thromboembolism (VTE) low molecular weight heparin (LMWH) is administered once or twice daily. A once daily treatment regimen is more convenient for the patient and may optimise home treatment. However, it is not clear whether a once daily treatment regimen is as safe and effective as a twice daily treatment regimen. This is the second update of a review first published in 2003.

OBJECTIVES

To compare the efficacy and safety of once daily versus twice daily administration of LMWH.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2013) and CENTRAL (2013, Issue 4).

SELECTION CRITERIA

Randomised clinical trials in which LMWH given once daily is compared with LMWH given twice daily for the initial treatment of VTE.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trials for inclusion and extracted data independently.

MAIN RESULTS

Five studies were included with a total of 1508 participants. The pooled data showed no statistically significant difference in recurrent VTE between the two treatment regimens (OR 0.82, 0.49 to 1.39; P = 0.47). A comparison of major haemorrhagic events (OR 0.77, 0.40 to 1.45; P = 0.41), improvement of thrombus size (OR 1.41, 0.66 to 3.01; P = 0.38) and mortality (OR 1.14, 0.62 to 2.08; P = 0.68) also showed no statistically significant differences between the two treatment regimens. None of the five included studies reported data on post-thrombotic syndrome.

AUTHORS' CONCLUSIONS

Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH.

Safety assessment and pharmacodynamics of a novel ultra low molecular weight heparin (RO-14) in healthy volunteers--a first-time-in-human single ascending dose study

INTRODUCTION

RO-14 is a novel ultra low molecular heparin. The purpose of this study was to evaluate the safety and pharmacodynamic profile of RO-14 in healthy males.

MATERIALS AND METHODS

We conducted a two-stage, single-center, open-label, randomized study. Two cohorts of 6 volunteers were randomly assigned to 12 single, ascending subcutaneous doses (1750-19950IU of anti-FXa activity) in an alternating crossover fashion. Safety was assessed by spontaneous/elicited adverse events, medical examination and laboratory tests. Anti-FXa activity and anti-FIIa activity were assessed throughout the 24hours after dosing. Dose proportionality and linearity of the anti-FXa activity were evaluated.

RESULTS

All doses were well tolerated and there were no bleeding events. At the lowest dose, anti-FXa activity A(max) was 0.16 (±0.02) IU/mL and AUC(0-24) was 1.11 (±0.24) IU*h/mL, At the highest dose anti-FXa activity A(max) was 1.67 (±0.15) IU/mL; AUC(0-24) was 21.48 (±4.46) IU*h/mL and t½ was 8.05h. Mean T(max) (all doses) was 2.86 (±0.39) h. RO-14 showed proportional and linear pharmacodynamics [normalized A(max) among doses (p=0.594) and normalized AUC(0-24) (p=0.092), correlations between A(max-)dose (R(2)=0.89, p<0.001) and AUC(0-24)-dose (R(2)=0.86, p<0.001)]. Anti-FIIa activity was below the detection limit (0.1IU/ml) at all dose levels. No clinically significant changes were observed in the platelet count, APTT, PT, TT, fibrinogen and antithrombin.

CONCLUSIONS

In this phase I study, RO-14 exhibited a good safety profile, anti-FXa activity for either prophylaxis or treatment of venous thromboembolism, linear pharmacodynamics, a longer elimination half-life than currently marketed low molecular weight heparin and no anti-FIIa activity.

Direct comparison of enoxaparin and nadroparin in a rabbit model of arterial thrombosis prevention

INTRODUCTION

The aim of the study was to evaluate and compare the efficacy of standard unfractionated heparin (UFH) and low-molecular weight heparins (LMWH's).

MATERIALS AND METHODS

We modified a previously published rabbit model of arterial thrombosis prevention [1,2] to compare unfractionated heparin and two different doses of two low-molecular weight heparin fragments--nadroparin and enoxaparin. Thrombosis in the distal aorta was triggered by vessel wall injury and critical stenosis. Blood flow in the damaged arterial segment was monitored by a flow probe placed distal to the constrictor. The primary endpoints of the study were: (1) cumulative flow, (2) time to occlusion and (3) residual clot weight. Thirty six animals were split into 6 groups with six animals in each group. Control groups were given saline or heparin and four more groups were used to compare LMWH's at 2 different doses.

RESULTS

In our study, all treatments were superior to the saline control group (alpha<or=0,01). Standard heparin was inferior (alpha<or=0,05) to both low molecular weight heparins for all primary endpoints (cumulative flow, time to occlusion and residual clot weight). There were no differences between the LMWH's except for cumulative flow at high doses.

CONCLUSIONS

This study revealed no relevant differences between nadroparin and enoxaparin for the primary endpoints of our model. Clinical use of each drug remains a personal preference.

Indirect comparisons of treatments based on systematic reviews of randomised controlled trials

BACKGROUND

Randomised controlled trials are the most effective way to differentiate between the effects of competing interventions. However, head-to-head studies are unlikely to have been conducted for all competing interventions.

AIM

Evaluation of different methodologies used to indirectly compare interventions based on meta analyses of randomised controlled trials.

METHODS

Systematic review of Cochrane Database of Systematic Reviews, Cochrane Methodology Register, EMBASE and MEDLINE for reports including meta analyses that contained an indirect comparison. Searching was completed in July 2007. No restriction was placed on language or year of publication.

RESULTS

Sixty-two papers identified contained indirect comparisons of treatments. Five different methodologies were employed: comparing point estimates (1/62); comparing 95% confidence intervals (26/62); performing statistical tests on summary estimates (8/62); indirect comparison using a single common comparator (20/62); and mixed treatment comparison (MTC) (7/62). The only methodologies that provide an estimate of the difference between the interventions under consideration and a measure of the uncertainty around that estimate are indirect comparison using a single common comparator and MTC. The MTC might have advantages over other approaches because it is not reliant on a single common comparator and can incorporate the results of direct and indirect comparisons into the analysis. Indirect comparisons require an underlying assumption of consistency of evidence. Utilising any of the methodologies when this assumption is not true can produce misleading results.

CONCLUSIONS

Use of either indirect comparison using a common comparator or MTC provides estimates for use in decision making, with the preferred methodology being dependent on the available data.

Are all low molecular weight heparins equivalent in the management of venous thromboembolism?

Low molecular weight heparins are replacing unfractionated heparin in a number of clinical indications because of their improved subcutaneous bioavailability and more predictable antithrombotic response. Clinical trials have demonstrated that low molecular weight heparins are at least as safe and effective as unfractionated heparin for the initial treatment of venous thromboembolism, and unfractionated heparin and warfarin for primary and secondary thromboprophylaxis. The mechanism behind the antithrombotic action of low molecular weight heparins is not fully understood but is likely to involve inhibition of coagulation factors Xa and IIa (thrombin), release of tissue-factor-pathway inhibitor, and inhibition of thrombin activatable fibrinolytic inhibitor. Different low molecular weight heparins have been shown to have various effects on coagulation parameters. Seven low molecular weight heparins are currently marketed worldwide, each demonstrated distinct chemical entities with unique pharmacokinetic and pharmacodynamic profiles. Each low molecular weight heparin is approved for specific indications based on the available efficacy and safety data for that product. The relative efficacy and safety of the low molecular weight heparins are unclear because there have been very few direct comparisons in randomized clinical trials. While recommending low molecular weight heparins for the prevention and treatment of venous thromboembolism, clinical guidelines have not specified individual agents. National and international organizations recognize that low molecular weight heparins are distinct entities and that they should not be used interchangeably in clinical practice. Each low molecular weight heparin should be used at the recommended dose when efficacy and safety data exist for the condition being treated. When these data are not available, the dosing and administration of low molecular weight heparins must be adapted from existing data and recommendations.

Ximelagatran for Treatment and Prophylaxis of Recurrent Events in Deep Vein Thrombosis

The treatment of acute venous thromboembolism and prophylaxis of recurrent events with heparin/low molecular weight heparin followed by vitamin K antagonists is limited by several factors. Oral direct thrombin inhibitors (ODTIs) showed a better pharmacological activity and might be an alternative in the treatment of venous thromboembolism. The Thrombin Inhibition in Venous Thromboembolism (THRIVE) program performed some studies developing the ODTI ximelagatran for this indication, and it is presented in the overview. The aim of the THRIVE I study was the dose finding, and that of the THRIVE IV study the applicability in hemodynamic stabile pulmonary embolism. A prospective, randomized, double blind trial was performed to compare oral ximelagatran with enoxaparin/warfarin for a 6-month treatment of acute venous thrombosis (THRIVE II and V). A second double blind study compared ximelagatran with placebo over 18 months after a 6-month anticoagulant therapy of acute deep vein thrombosis. The efficacy and safety of treatment of patients with acute deep venous thrombosis who received 2 ∞ 36 mg ximelagatran was not inferior to that of patients who received a conventional anticoagulant for prophylaxis of recurrent events over 6 months. Ximelagatran 2 ∞ 24 mg significantly reduced recurrent thromboembolic events compared to placebo without increasing the risk for hemorrhage. A reversible symptomless increase of alanine aminotransferase occurs in 6% to 9.6% of patients between months 2 and 4. The results of the follow-up studies suggest that thromboembolic events may recur in patients with acute venous thromboembolism after termination of treatment with both vitamin K antagonists and ximelagatran.

Management of venous thromboembolism: a clinical practice guideline from the American College of Physicians and the American Academy of Family Physicians

Venous thromboembolism is a common condition affecting 7.1 persons per 10,000 person-years among community residents. Incidence rates for venous thromboembolism are higher in men, African-Americans, and increase substantially with age. It is critical to treat deep venous thrombosis at an early stage to avoid development of further complications, such as pulmonary embolism or recurrent deep venous thrombosis. The target audience for this guideline is all clinicians caring for patients who have been given a diagnosis of deep venous thrombosis or pulmonary embolism. The target patient population is patients receiving a diagnosis of pulmonary embolism or lower-extremity deep venous thrombosis.

Anticoagulant Treatment of Deep Vein Thrombosis and Pulmonary Embolism

Venous thrombosis is a common disease. As the mean age of the population increases, so does the incidence of venous thromboembolism. Anticoagulant therapy is equally effective in young and older patients, and can reduce substantially the associated morbidity and mortality. When considering long-term oral anticoagulant therapy in older patients, however, careful ongoing evaluation is imperative to ensure that the risk of bleeding does not outweigh the antithrombotic benefits.

Once versus twice daily LMWH for the initial treatment of venous thromboembolism

BACKGROUND

In the initial treatment of venous thromboembolism (VTE) low molecular weight heparin (LMWH) is administered once or twice daily. A once daily treatment regimen is more convenient for the patient and may optimise home treatment. However, it is not clear whether a once daily treatment regimen is as safe and effective as a twice daily treatment regimen.

OBJECTIVES

To compare the efficacy and safety of once daily versus twice daily administration of LMWH.

SEARCH STRATEGY

We identified trials through searching the Specialised Register of the Cochrane Peripheral Vascular Diseases Group (last searched April 2005), the Cochrane Central Controlled Trials Register (CENTRAL) (last searched Issue 2, 2005), handsearches of relevant journals, checking cross-references and through personal communication with experts.

SELECTION CRITERIA

Randomised clinical trials in which LMWH given once daily is compared to LMWH given twice daily for the initial treatment of venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Two authors assessed trials for inclusion and extracted data independently.

MAIN RESULTS

Five studies were included with a total of 1508 participants. The pooled data showed a statistically non-significant difference in recurrent venous thromboembolism between the two treatment regimens (OR 0.82, 0.49 to 1.39). A comparison of major haemorrhagic events (OR 0.77, 0.40 to 1.45) and mortality (OR 1.14, 0.62 to 2.08) also showed a statistically non-significant difference between the two treatment regimens.

AUTHORS' CONCLUSIONS

Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH. However, the 95% confidence interval implies that there is a possibility that the risk of recurrent VTE might be higher when people are treated once daily. Hence, the decision to treat a person with a once daily regimen will depend on the evaluated balance between increased convenience and the potential for a lower efficacy.

Prophylaxis and treatment of deep vein thrombosis in general surgery

BACKGROUND

Patients undergoing general surgery present an inherent risk of deep vein thrombosis (DVT). Evidence-based strategies for prevention and treatment of DVT should be continuously upgraded on the basis of good-quality recent trials.

DATA SOURCES

Articles were identified using MEDLINE, EMBASE, and the Cochrane Library databases (January 1980 to July 2003). Randomized clinical trials and meta-analyses in which different prophylactic and treatment methods were compared for general surgery patients were selected.

CONCLUSIONS

In general surgery, low-molecular weight heparins (LMWHs) are relied upon more and more for prophylaxis and initial anticoagulant treatment of DVT, because of their multiple advantages in efficacy, safety, and convenience in handling. For cost-effective reasons, full-dose vitamin K antagonists are still preferred as the standard long-term anticoagulation method, while LMWHs represent the exception. Long-term use of low-intensity warfarin should be considered a new standard of care for the management of venous thrombosis. Compared to LMWH, the new anticoagulant molecules fondaparinux and ximelagatran seem to have similar efficacy in the treatment of venous thromboembolism, but they have a 2-fold increased efficacy in its prophylaxis. Clinical implementation of these new anticoagulant molecules depends on their cost-effectiveness; however, they have the potential to become the treatment of choice in the next decade. Thrombolysis has an unacceptable risk of hemorrhagic complications when used in the treatment of postoperative DVT. Furthermore, there are no data to prove that thrombolysis reduces the incidence of postthrombotic syndrome (PTS), despite early and complete recanalization achieved by thrombolysis. Surgical thrombectomy is only meant to decompress the venous hypertension consecutive to massive thrombosis (phlegmasia cerulea dolens) and thus to avoid venous gangrene. Other mechanical percutaneous thrombectomy devices are under evaluation. In selected cases, a combination treatment consisting of locoregional thrombolysis of the crurofemoral venous axis and mechanical thrombectomy of the pelvic venous axis achieves high rates of complete desobliteration.

Initial Treatment of Venous Thromboembolism

Adequate initial anticoagulant therapy of deep venous thrombosis (DVT) is required to prevent thrombus growth and pulmonary embolism (PE). Intravenous unfractionated heparin (UFH) is being replaced by low-molecular-weight heparin (LMWH) as the anticoagulant of choice for initial treatment of venous thromboembolism (VTE). Both agents are relatively safe and effective when used to treat VTE, with LMWH suitable for outpatient therapy because of improved bioavailability and more predictable anticoagulant response. Serious potential complications of heparin therapy, such as heparin-induced thrombocytopenia (HIT) and osteoporosis, seem less common with LMWH. The potential for fetal harm and changes in maternal physiology complicate the treatment of VTE during pregnancy. Although systemic thrombolysis is used in patients with massive PE and in some patients with proximal DVT, controversy persists with respect to appropriate patient selection for this intervention.

Treatment of venous thromboembolism with low-molecular-weight heparin: a synthesis of the evidence published in systematic literature reviews

OBJECTIVE

To evaluate the methodology and cumulative evidence presented in systematic reviews of clinical trials comparing low-molecular-weight heparin (LMWH) with unfractionated heparin (UFH) for the treatment of venous thromboembolism.

METHODS

We reviewed all systematic reviews of clinical trials published until March 2002. Fourteen systematic literature reviews were published between 1994 and 2000. Deficiencies in methodological quality were common, particularly in the description of search strategies, assessment of clinical trial quality, and methods used to combine results.

RESULTS

Results of reviews indicate that LMWH is superior to UFH for the treatment of venous thromboembolism, particularly in reducing mortality. Patients with isolated deep venous thrombosis or deep venous thrombosis with concomitant pulmonary embolism seemed to have similar benefit. However, the benefits of LMWH over UFH were smaller in magnitude in reviews that included more recent clinical trials.

Outpatient therapy with low molecular weight heparin for the treatment of venous thromboembolism: a review of efficacy, safety, and costs

PURPOSE

To summarize the evidence comparing the efficacy, safety, and costs of outpatient and inpatient treatment of venous thromboembolism.

METHODS

We searched the literature through March 2002 for studies comparing outpatient and inpatient treatment of venous thromboembolism with low molecular weight heparin or unfractionated heparin, and for studies addressing the costs of low molecular weight heparin use in any setting. We included studies with comparison groups or decision analyses.

RESULTS

Eight studies (three randomized trials and five cohort studies) compared outpatient use of low molecular weight heparin with inpatient use of unfractionated heparin in 3762 patients. The incidence of recurrent deep venous thrombosis was similar in the two groups (median, 4% [range, 0% to 7%] vs. 6% [range, 0% to 9%]), as was major bleeding (median, 0.5% [range, 0% to 2%] vs. 1% [range, 0% to 2%]). Use of low molecular weight heparin was associated with shorter hospitalization (median, 2.7 days [range, 0.03 to 5.1 days] vs. 6.5 days [range, 4 to 9.6 days]) and lower costs (median difference, 1600 dollars). Comparisons of outpatient and in-hospital use of low molecular weight heparin reported no difference in outcomes, but there were savings in hospitalization costs. Low molecular weight heparin was also found to be more cost saving and cost-effective than unfractionated heparin, with savings of 0% to 64% (median, 57%).

CONCLUSION

The evidence indicates that outpatient treatment of deep venous thrombosis with low molecular weight heparin is likely to be efficacious, safe, and cost-effective.

Enoxaparin versus tinzaparin in non-ST-segment elevation acute coronary syndromes: the EVET trial

BACKGROUND

Low-molecular weight heparins have different pharmacokinetic and pharmacodynamic characteristics and may vary in efficacy. We compared the efficacy of enoxaparin with that of tinzaparin in the management of non-ST-segment elevation acute coronary syndromes (NSTACS).

METHODS

A total of 438 patients with NSTACS were randomized to receive subcutaneous treatment with enoxaparin, 100 IU/kg twice daily (equivalent to 1 mg/kg twice daily; n = 220), or tinzaparin, 175 IU/kg once daily, (n = 218) for as long as 7 days. The primary composite end point was recurrent angina, myocardial infarction (or reinfarction), or death at day 7. Secondary end points were the primary end point at day 30 and the occurrence of individual events at days 7 and 30.

RESULTS

The incidence of the primary end point was 12.3% in the enoxaparin group and 21.1% in the tinzaparin group (P =.015). At day 7, the rate of recurrent angina was lower with enoxaparin than with tinzaparin (11.8% vs 19.3%). At day 30, the incidences of the composite end point, recurrent angina, and myocardial infarction were also lower with enoxaparin, 17.7% vs 28.0% (P =.012), 17.3% vs 26.1% and 0.5% vs 2.8%, respectively. The rate of revascularization was lower in the enoxaparin group, 8.6% vs 17.9% (P =.010) at day 7 and 16.4% vs 26.1% (P =.019) at day 30. Rates of bleeding complications were similar in the 2 treatment groups.

CONCLUSIONS

This study indicates a benefit of enoxaparin (100 IU/kg twice daily) as compared with tinzaparin (175 IU/kg once daily) in the treatment of patients with NSTACS, which is sustained for at least 30 days.

Once versus twice daily LMWH for the initial treatment of venous thromboembolism

BACKGROUND

In the initial treatment of venous thromboembolism (VTE) low molecular weight heparin (LMWH) is administered once or twice daily. A once daily treatment regimen is more convenient for the patient and may optimise home treatment. However it is not clear whether a once daily treatment regimen is as safe and effective as a twice daily treatment regimen.

OBJECTIVES

The objective of this review was to compare the efficacy and safety of once daily administration to a twice daily administration of LMWH.

SEARCH STRATEGY

Trials were identified through the Specialised Register of the Cochrane Peripheral Vascular Diseases Group (last searched May 2001), the Cochrane Controlled Trials Register (CCTR/CENTRAL) (last searched Issue 1, 2002), by hand-searching other relevant journals, by checking cross-references and through personal communication with experts.

SELECTION CRITERIA

Randomised clinical trials in which a once daily treatment regimen with LMWH is compared to a twice daily regimen in the initial treatment of patients with venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trials on criteria for inclusion and extracted the data independently.

MAIN RESULTS

Five studies were included with a total of 1508 patients. The pooled data showed a statistically non-significant difference in recurrent venous thromboembolism between the two treatment regimens (OR 0.82; 0.49 - 1.39). A comparison of major haemorrhagic events (OR 0.77; 0.40 - 1.45) and mortality (OR 1.14; 0.62 - 2.08) also showed a statistically non-significant difference between the two treatment regimens.

REVIEWER'S CONCLUSIONS

Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH. However, the 95% confidence interval implies that there is a possibility that the risk of recurrent VTE might be higher when patients are treated once daily. Hence the decision to treat the patient with a once daily regimen will depend on the evaluated balance between increased convenience and the potential for a lower efficacy.

Fixed-dose versus adjusted-dose low molecular weight heparin for the initial treatment of patients with deep venous thrombosis

Patients with acute deep vein thrombosis (DVT) were treated with a body-weight independent dosage of 2 x 8000 aXa IU low-molecular-weight heparin (LMWH) Certoparin. After the subcutaneous administration of 8000 IU Certoparin, pharmacodynamic parameters did not differ between patients and healthy volunteers, and the AUC of the anticoagulant effects were not related to body weight. Two clinical trials demonstrated a greater regression of thrombi and a lower occurrence of recurrent venous thromboembolism (VTE), major bleeding, and mortality within 14 days of initial therapy compared with intravenous heparin. D-dimer decreased, and anti-Xa activity increased in those patients with a regression of thrombosis. The benefit of the reduced occurrence of recurrent VTE, major bleeding, and mortality was maintained up to 6 months. Major bleeding was not related to the body weight in either treatment group. Treatment of acute DVT in adults with fixed dose of 2 x 8000 aXa IU LMWH Certoparin is more effective and safer than heparin.

Current management of acute symptomatic deep vein thrombosis

Venous thromboembolism is a common and potentially fatal disease. If properly used, anticoagulation therapy is effective in preventing recurrence of venous thromboembolism and in improving survival. Symptomatic patients with an objective diagnosis of acute deep vein thrombosis (DVT) or pulmonary embolism (PE) should receive immediate systemic heparin anticoagulation at dosages sufficient to rapidly prolong the activated partial thromboplastin time into the laboratory-specific therapeutic range; this range corresponds to a plasma heparin concentration of 0.2 to 0.4 IU/ml (as measured by protamine sulfate titration), or 0.3 to 0.7 anti-Xa IU/ml. An oral vitamin K antagonist (e.g. warfarin) should be started within 24 hours after starting heparin; the starting dose should be the estimated patient-specific daily dose with no loading dose. Heparin and warfarin anticoagulation should be overlapped for at least 4 to 5 days and until the international normalized ratio (INR) is within the therapeutic range (2.0 to 3.0) on 2 measurements made at least 24 hours apart. The duration of warfarin anticoagulation should be individualized based on the respective risks of venous thromboembolism recurrence and anticoagulant-related bleeding. In general, warfarin should be continued for at least 3 months, and longer for patients with recurrent or idiopathic venous thromboembolism, malignant neoplasm, neurologic disease with extremity paresis, obesity, or laboratory evidence of a lupus anticoagulant/anticardiolipin antibody, homozygous carrier or combined heterozygous carrier for the factor V R506Q (Leiden) and prothrombin G20210A mutations, and possibly deficiency of either antithrombin, protein C, or protein S. Low molecular weight heparin (LMWH) is effective and well tolerated as acute therapy for patients with DVT or stable PE, and does not require laboratory monitoring or dose adjustment. Outpatient LMWH therapy is also well tolerated and cost effective for most patients with DVT, and possibly for selected patients with PE.