Subcutaneous low-molecular-weight heparin compared with continuous intravenous heparin in the treatment of proximal-vein thrombosis

Tinzaparin: considerations for use in clinical practice

OBJECTIVE

To evaluate the safety and effectiveness of tinzaparin for the prevention and treatment of venous thromboembolism (VTE).

DATA SOURCES

A MEDLINE and PubMed database search (1980-December 2002) was conducted. Only articles written in English were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Articles reporting the safety, efficacy, and cost-effectiveness of tinzaparin in humans were evaluated. Emphasis was placed on randomized, controlled trials.

DATA SYNTHESIS

Tinzaparin sodium is a low-molecular-weight heparin (LMWH) that exerts its anticoagulant effect through inhibition of factors Xa and IIa and release of tissue factor pathway inhibitor from the vascular epithelium. Tinzaparin is indicated for treatment of acute symptomatic deep-vein thrombosis (DVT), with or without pulmonary embolism. Clinical studies suggest that tinzaparin is also effective for VTE prophylaxis, as well as other indications. Once-daily subcutaneous tinzaparin is equally or more effective than intravenous unfractionated heparin (UFH) for prevention and treatment of VTE, at least as safe as UFH for bleeding complications, and requires little or no monitoring. No dose "cap" is required for obese patients, and no initial dosing adjustments are necessary in elderly and/or renally impaired patients, although some monitoring is recommended. The few comparative data available suggest that tinzaparin efficacy may be comparable to that of other LMWHs; more comparative studies are needed. Pharmacoeconomic studies indicate a favorable cost-benefit ratio.

CONCLUSIONS

Tinzaparin is safe and effective for prevention and treatment of DVT. Consistent once-daily dosing may facilitate self-administration of tinzaparin in the outpatient setting.

Deep venous thrombosis: a new task for primary health care. A randomised economic study of outpatient and inpatient treatment

OBJECTIVE

A health economic evaluation of two alternative treatment settings, inpatient care and outpatient care, for acute deep venous thrombosis.

DESIGN

A randomised multicentre trial in a defined population in regular clinical practice.

SETTING

Hospitals and related health care centres in the Jönköping county council in Sweden.

INTERVENTIONS

Patients were randomised to either an inpatient strategy (n = 66) or an outpatient strategy (n = 65) using low-molecular-weight heparin, dalteparin, administered subcutaneously once daily and adjusted for body weight.

SUBJECTS

Of 224 eligible patients, 131 entered the trial and 124 completed the economic part of the study.

MAIN OUTCOME MEASURES

Direct medical and direct non-medical costs during a 3-month period.

RESULTS

Total direct costs were higher for those in the inpatient strategy group, i.e. Swedish Crowns (SEK) 16400 per patient (Euro 1899) compared to SEK 12100 per patient (Euro 1405) in the outpatient strategy group (p < 0.001). More patients in the outpatient group received assistance when they returned home. Few patients in either group reported sick leave. There was no difference in total number of days between the two groups.

CONCLUSIONS

Total direct costs were significantly lower for the outpatient treatment strategy for deep venous thrombosis compared to the inpatient treatment strategy. No significant difference in health impact could be detected. Deep venous thrombosis can to a greater extent than previously be treated in primary care, safely, at a lower cost, and in accordance with patient preferences.

Tinzaparin sodium for thrombosis treatment and prevention during pregnancy

OBJECTIVE

This study was undertaken to assess the pharmacodynamic profile, safety, and efficacy of tinzaparin during pregnancy.

STUDY DESIGN

Fifty-four pregnant women, 12 for treatment of thrombosis and 42 for thromboprophylaxis, received tinzaparin by once daily injection. Four-hour postdose anti-Xa results were analyzed by use of repeated measures statistical methods.

RESULTS

One woman (3.4%) on the 175 anti-Xa U/kg dose and three women (20%) on the 50 anti-Xa U/kg dose required a dose increase during the initial dose titration phase to achieve target anti-Xa activity. No thrombotic events occurred.

CONCLUSION

The 175 anti-Xa U/kg dose is appropriate for treatment and for high-risk thromboprophylaxis throughout pregnancy. In pregnant women at moderate risk of thrombosis, a higher tinzaparin dose is required than in the nonpregnant state and 75 anti-Xa U/kg appears to be appropriate. The majority of women do not need a dose increase with advancing gestation.

A novel long-acting synthetic factor Xa inhibitor (SanOrg34006) to replace warfarin for secondary prevention in deep vein thrombosis. A Phase II evaluation

BACKGROUND

Vitamin K antagonists for secondary prevention in patients with deep vein thrombosis (DVT) require monitoring and dose adjustments. The synthetic factor Xa inhibitor, SanOrg34006, has predictable pharmacokinetics and may be administered once weekly without dose adjustments.

METHODS

After 5-7 days of enoxaparin treatment, patients with proximal DVT were randomized to receive 2.5, 5.0, 7.5 or 10 mg of SanOrg34006 subcutaneously once weekly or warfarin (INR, 2.0-3.0) for 12 weeks. The primary efficacy outcome was the composite of change in thrombotic burden, as assessed by ultrasonography and perfusion lung scanning at baseline and week 12 +/- 1, and clinical thromboembolic events. This outcome was classified as normalization, no relevant change, or deterioration. Other outcomes were major and other clinically relevant bleeding.

RESULTS

A total of 659 patients were randomized and treated. In 614 (93%) patients the primary efficacy outcome was evaluable. The rates of normalization and deterioration were similar in all SanOrg34006 groups (P = 0.4) and did not differ from the warfarin group. There was a clear dose-response for major bleeding among patients treated with SanOrg34006 (P = 0.003). Patients receiving 2.5 mg SanOrg34006 had less bleeding than did warfarin recipients (P = 0.03).

CONCLUSIONS

SanOrg34006 dosed at 2.5 mg appears as effective as higher dosages and warfarin for secondary prevention in DVT and was not associated with major bleeding. Therefore, 2.5 mg of SanOrg34006 administered subcutaneously once weekly might be a suitable alternative to dose-adjusted oral vitamin K antagonist.

Tissue factor, thrombin, and cancer

In addition to its primary role in hemostasis and blood coagulation, thrombin is a potent mitogen capable of inducing cellular functions. Therefore, it should come as no surprise that thrombin has proved to be of importance in the behavior of cancer. In this review, we focus on the ability of tissue factor (TF) and thrombin to influence tumor angiogenesis. Both exert their influence on angiogenesis through clotting-dependent and clotting-independent mechanisms: (1). directly affecting signaling pathways that mediate cell functions, and (2). mediating clot formation, thereby providing a growth media for tumor cells. Therefore, anticoagulant drugs may prove efficacious in cancer treatment due to their ability to reduce the characteristic hypercoagulability of cancer and alter the fundamental biology of cancer.

The use of low molecular weight heparin to predict clinical outcome in patients with unstable angina that had undergone percutaneous coronary intervention

BACKGROUND

Antithrombotic therapy with heparin reduces the rate of ischemic events in patients with acute coronary syndrome. Low-molecular-weight heparin, given subcutaneously twice daily, has a more predictable anticoagulant effect than standard unfractionated heparin. Moreover, it is easier to administer and does not require monitoring.

METHODS

We prospectively analyzed 180 patients with unstable angina who had undergone percutaneous coronary intervention (PCI) between 1999 and 2001 at Chonnam National University Hospital and had received either 120 U/kg of dalteparin (Fragmin), administered subcutaneously twice daily (Group I; n = 90, 61.8 +/- 8.9 years, male 67.8%), or had received continuous intravenous unfractionated heparin (Group II; n = 90, 62.6 +/- 9.7 years, male 70.0%). During hospitalization and at 6 month after PCI, major adverse cardiac events such as acute myocardial infarction, target vessel revascularization, death, and restenosis were examined.

RESULTS

During hospitalization, the incidence of acute myocardial infarction, target vessel revascularization and death were not different between the two groups. At follow-up coronary angiography 6 months after PCI, the incidence of restenosis was lower in group I than in group II (Group I; 26/90, 28.8% vs. Group II; 32/90, 35.6%, p = 0.041) and the incidence of target vessel revascularization was lower in group I than in group II (Group I; 21/90, 23.3% vs. Group II; 27/90, 30.0%, p = 0.039). No difference was found in the rates of major and minor hemorrhages, ischemic strokes or thrombocytopenia between two groups. By multivariate analysis, the factors related to restenosis were lesion length, postprocedural minimal luminal diameter, CRP on admission, diabetes mellitus, the type of heparin, and stent use.

CONCLUSION

Dalteparin, a low molecular weight heparin, is superior to standard unfractionated heparin in terms of reducing the restenosis rate and target vessel revascularization without increasing bleeding complications.

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.

Unresolved issues in anticoagulant therapy

Large randomized clinical trials have clarified some issues of anticoagulation and have led to progress, such as outpatient treatment of acute deep vein thrombosis with low-molecular-weight heparin. However, many uncertainties remain and are reviewed here. When should thrombolytic therapy be used, apart from patients in shock due to pulmonary embolism? How should low-molecular-weight heparin be used in patients with extreme obesity or renal failure? The optimal duration of anticoagulation after venous thromboembolism has been the subject of many debates. With the recognition of an increasing number of risk factors for recurrence, the picture becomes increasingly complex. Lower intensity of anticoagulation with vitamin K antagonists and novel anticoagulant drugs are possible alternatives in extended secondary prophylaxis. For stroke prophylaxis in non-valvular atrial fibrillation, there is a gray zone between the groups where there is a clear indication for aspirin or for vitamin K antagonists. Anticoagulation in connection with cardioversion raises questions regarding optimal postprocedure therapy. Fine tuning of prophylaxis against thromboembolism in patients with prosthetic heart valves requires more studies of subgroups, homogenous for position and type of valve as well as presence of atrial fibrillation. The management of these patients in case of surgical procedures has not been studied properly. Secondary prophylaxis after myocardial infarction may achieve the best effect with vitamin K antagonists at an INR of 2.0-2.5 in combination with low-dose aspirin, but is it really cost-effective? Finally, many controversies exist regarding anticoagulation during pregnancy.

Hospital guidelines for use of low-molecular-weight heparins

OBJECTIVE

To describe the development of guidelines for initial use of low-molecular-weight heparins (LMWHs) and other anticoagulants in acute-care hospitals that are part of a national group purchasing organization (GPO).

DATA SOURCES

A systematic literature search (1970-December 2001) was conducted to identify evidence on the efficacy of various anticoagulants for initial therapy in deep-vein thrombosis and pulmonary embolism, and in treatment of acute coronary syndrome. A group consensus method was then used to develop guidelines. Guidelines were reviewed and revised by an internal expert panel as well as an external expert panel. Final guidelines were disseminated to GPO members and assistance was provided with implementation at the local level.

RESULTS

The final set of guidelines is described. The guidelines are organized based on recommended therapeutic options for each indication. For each option, consensus opinion is provided on the level of evidence that exists in the literature, comparisons of cost and convenience, and additional dosing information. The guidelines were disseminated along with supporting material to interested GPO member hospitals, and teleconferences were held to facilitate implementation at the local level. The guidelines were initially implemented at 18 hospitals across the country.

CONCLUSIONS

The process by which these guidelines were developed, plus the final set of guidelines, may be useful to hospitals and healthcare systems contemplating or engaged in a similar effort with this class of drugs.

Low-molecular-weight heparin (reviparin) diminishes tumor cell adhesion and invasion in vitro, and decreases intraperitoneal growth of colonadeno-carcinoma cells in rats after laparoscopy

BACKGROUND

Metastases, adhesion and invasion of tumor cells involve a cascade of complex phenomena, which potentially can be affected by glycosaminoglycans. We studied the influence of a low-molecular-weight heparin, reviparin, on the intraabdominal tumor growth in rats undergoing laparoscopy. We also studied cytotoxicity, anti-adhesive, and anti-invasive effects of reviparin in vitro using adenocarcinoma cells CC531.

METHODS

In vitro assays: Adhesion of 1 x 10(5) CC531 adenocarcinoma cells onto microtiter plates coated with 10 microg/ml collagen type I or 10 microg/ml Matrigel was studied in the presence of 0.55; 1.10 and 2.76 mg/ml reviparin, and compared to saline. The cytotoxicity of 1 x 10(4) adenocarcinoma cells was studied in a similar assay. Transwell dual chambers with polycarbonate filters coated with 100 microg/cm2 Matrigel were used to investigate the effect of 0.55; 1.10 and 2.76 mg/ml reviparin on the invasion of 1 x 10(5) adenocarcinoma cells/ml. In vivo experiments: CC531 adenocarcinoma cells (5 x 10(6) cells/ml) were intraperitoneally applied to Wistar Albino Glaxo rats (n=150, Harlan, Germany) with a median weight of 278 g. The rats were divided into 15 groups with 10 animals in each group, underwent laparoscopy, and 1 ml saline containing 0, 0.5, 2.0, 4.0, and 10 mg reviparin per kg b.w. was introduced for intraperitoneal lavage or s.c. After 21 days the animals underwent an autopsy, and the tumor weight was determined.

RESULTS

In vitro experiments: We found a highly significant inhibition of tumor cell adhesion and invasion (p<0.001) by all reviparin concentrations used in the assays. There was no effect of reviparin on the viability of cells in the cytoxicity assay. In vivo experiments: We found that application of 4.0 and 10.0 mg/kg b.w., but not 0.5 or 2.0 mg/kg b.w. significantly (p<0.01) decreased the tumor mass compared to controls, receiving only saline. This effect was most pronounced after the combined i.p. and s.c. application, whereas after a sole i.p. application, only the highest dose of 10 mg/kg b.w. caused a significant inhibition of tumor growth.

CONCLUSION

Low-molecular-weight heparin, reviparin, given in combination of i.p. lavage and s.c. injections, significantly diminishes intraabdominal tumor growth of CC531 adenocarcinoma cells in rats undergoing laparoscopy. This may offer additional therapeutic options for patients undergoing laparoscopic cancer surgery.

Splenic spontaneous rupture (SSR) and hemoperitoneum associated with low molecular weight heparin: a case report

We describe the first case of spontaneous splenic rupture associated with tinzaparin in a cancer patient. This low-molecular-weight heparin was administrated for deep venous thrombosis and pulmonary embolism. No underlying splenic pathology predisposing to this condition was found.

Outpatient treatment of acute venous thromboembolic disease

Once- or twice-daily subcutaneous dosing of LMWHs without laboratory monitoring has facilitated outpatient VTE therapy. Clinical trials have demonstrated at least equivalent efficacy and safety and potential cost savings of outpatient therapy for uncomplicated proximal DVT with LMWH when compared with inpatient therapy. Explicit criteria exist for outpatient DVT therapy. Home therapy for PE requires further evaluation before it can be recommended outside of a trial or other supervised setting.

Venous thromboembolism in intensive care patients

Venous thromboembolism frequently complicates the management of patients with severe medical and surgical illnesses. Because the diagnosis of VTE is especially challenging in critically ill patients, the focus of intensivists should be on characterization of risk factors and the appropriate choice of VTE prophylaxis. LDUH or LMHW is the preferred choice for VTE prophylaxis in ICU patients. Mechanical methods of prophylaxis should be reserved for patients with a high risk for bleeding. The effectiveness of mechanical methods and of combined strategies of prevention and the clinically important outcomes of therapy need to be explored further in critically ill patients. Few diagnostic strategies have been assessed in ICU patients with suspected PE. Ventilation-perfusion lung scans remain a pivotal diagnostic test but retain the same limitations in critically ill patients as seen in other patient populations. Newer noninvasive techniques, such as spiral CT associated with imaging of the extremities, are gaining more wide-spread use, but, thus far, pulmonary angiography remains the most reliable technique to confirm or exclude PE in patients with respiratory failure. A consensus must be reached regarding the most appropriate combination of tests for adequate and cost-effective diagnosis of VTE. Further investigation of diagnostic strategies that include adequate consideration of clinical diagnosis using standardized models and noninvasive imaging are warranted.

Deep venous thrombosis after total hip or knee arthroplasty in a "low-risk" Chinese population

Scarcely any information has been published on deep vein thrombosis (DVT) in Chinese patients after total hip arthroplasty (THA) or total knee arthroplasty (TKA). However, generally, no prophylaxis is given to patients who do not have conventional high-risk factors because they are believed to be at "low risk." We performed a prospective study on 80 such "low risk" patients undergoing THA or TKA (58 TKA and 22 THA) without prophylaxis and performed duplex ultrasonography on both lower limbs 6 to 8 days after surgery. A total of 22 patients (27.5%) showed ultrasonographic evidence of DVT. Eighteen (31%) TKAs and 4 (18.1%) THAs were complicated by DVT. Three patients showed bilateral involvement, all of whom underwent TKA. Two patients had symptomatic pulmonary embolism. The sensitivity and positive predictive value of the clinical examination was 27.2% and 31.6%, respectively. This study showed that patients who are labeled "low risk" for DVT actually had a significant risk and suggests that the current practice of providing prophylaxis to only patients deemed at "high risk" should be revised.

Thromboprophylaxis and thrombosis in medical, surgical, trauma, and obstetric/gynecologic patients

The International Consensus and the ACCP Sixth Consensus had a great impact on the clinical acceptance of LMWHs. These recommendations have been instrumental in initiating further clinical trial to answer key questions regarding thromboprophylaxis and in setting a new standard for patient care. Also, the key to cost containment in management of DVT/PE is to (1) define the etiology (blood coagulation protein or platelet defect), institute appropriate long-term therapy as indicated, and assess appropriate family members as indicated if a hereditary defect is found and (2) use LMWH as inpatient management. saving a minimum of 210,000.00 dollars per 1000 patients simply from cost savings of recurrence, saving 17 lives per 1000 patients, and saving exorbitant costs of care for patients with recurrence and development of chronic venous insufficiency. The use of outpatient LMWH will save 4,900,000.00 dollars per 1000 patients if applied to the 70% of patients with DVT who fit the criteria of no comorbid condition requiring hospitalization and who arrive early enough to allow a diagnosis to be sent home or hospitalized for 24 hours or less. The simple defining of defects leading to unexplained thrombosis will add another 3,000,000.00 dollars in savings per 1000 patients with DVT and approximately 350,000.00 dollars per 100 patients with thrombotic stroke. In those with transient ischemic attacks, defining the defect and instituting appropriate antithrombotic therapy, thereby potentially saving approximately 30% from developing a thrombotic stroke, amounts to approximately 350,500.00 dollars (= 30% of 1,168,500.00 dollars) in savings per 100 patients.

Safety of low molecular weight heparins in the treatment of venous thromboembolism

Low molecular weight heparins (LMWHs) are commonly employed as a substitute for unfractionated heparin (UFH) in the treatment of venous thromboembolic events. Despite their higher cost, the preferential use of LMWHs seemed justified initially as, based on the results of earlier meta-analyses, these compounds were deemed to be more effective and safer than UFH. Although, in this respect, their purported superiority over UFH could not be confirmed by subsequent large, randomised trials and updated meta-analyses, other peculiar features of LMWHs were highlighted, favouring their preferential utilisation in patients with venous thromboembolism. Among these, the possibility of once-daily administration on an out-patient basis, the lower incidence of Type II heparin-induced thrombocytopenia and the lower likelihood of osteoporosis after prolonged treatment periods, appear to be especially prominent. This review attempts to evaluate the available evidence focusing on the safety of LMWHs for the treatment of venous thromboembolism and the current therapeutic options and potential advantages of LMWHs, either in general or in selected patient populations.

A randomized, controlled, dose-guiding study of the oral direct thrombin inhibitor ximelagatran compared with standard therapy for the treatment of acute deep vein thrombosis: THRIVE I

This randomized, controlled, multicentre study evaluated the efficacy and tolerability of the oral direct thrombin inhibitor ximelagatran, compared with a low-molecular-weight heparin (dalteparin) followed by warfarin, in the treatment of deep vein thrombosis (DVT) of the lower extremity. Patients with acute DVT received oral ximelagatran (24, 36, 48 or 60 mg twice daily) or dalteparin and warfarin for 2 weeks. Evaluation of paired venograms from 295 of 350 patients showed regression of the thrombus in 69% of patients treated with ximelagatran and 69% of patients treated with dalteparin and warfarin. Progression was observed in 8% and 3% of patients, respectively. Changes in thrombus size according to the Marder score were similar in all groups. Treatment discontinuation due to bleeding occurred in two patients receiving ximelagatran (24- and 36-mg groups) and in two patients receiving dalteparin and warfarin. Reduction in pain, edema and circumference of the affected leg was similar in all groups. Oral ximelagatran appears to be a promising alternative to current anticoagulant therapy to limit the progression of acute DVT, and it seems to possess a wide therapeutic window.

Current pharmacotherapeutic options for treating deep vein thrombosis

The treatment of deep vein thrombosis (DVT) has been evolving over the past 50 years. Initially, unfractionated heparin (UFH) given subcutaneously every 6 h, progressed to constant infusion therapy followed by warfarin, which has become the mainstay of therapy. Over the past 12 years, a new therapy, low molecular weight heparin (LMWH), has proven to be at least as effective or more effective than UFH in the acute treatment of DVT. These drugs are administered subcutaneously, are better absorbed and do not require monitoring. LMWHs have changed the paradigm of caring for patients with DVT. Finally a number of studies with thrombolytic agents have attempted to improve the outcome of DVT by reducing clot burden and preventing the sequelae of thrombotic valvular damage. This paper will review the management of DVT from the acute phase to long-term management.

Treatment and management of acute venous thromboembolic disease

Venous thromboembolic (VTE) disease consists of deep vein thrombosis and/or pulmonary embolism. Either low molecular weight heparin given subcutaneously or unfractionated heparin administered intravenously are used for the initial treatment. Simultaneously, warfarin therapy is initiated. Thrombolytic therapy plays a limited role. Following the initial heparin treatment, anticoagulation clinics provide an excellent means of monitoring the oral anticoagulation. Patient education is important and patients should be well versed in the basic features of oral anticoagulation. The duration of oral anticoagulation is dependent on a number of factors including the presence of inherited risk factors, bleeding risk and patient reliability. Residual thrombus in the affected vein may indicate the need for prolonged anticoagulation. The low intensity oral anticoagulation (INR 1.5-2.0) is useful in preventing recurrent thrombosis following the initial treatment period with full intensity oral anticoagulation.

Signs of thrombin generation in pediatric cardiac catheterization with unfractionated heparin bolus or subcutaneous low molecular weight heparin for antithrombotic cover

INTRODUCTION

Thrombosis is one of the most frequent adverse events after cardiac catheterization, which can be reduced by anticoagulation with unfractionated heparin (UFH) in both children and adults. Low molecular weight heparin (LMWH) might possibly offer advantages. Laboratory signs of thrombin generation during pediatric cardiac catheterization, with unfractionated heparin (UFH) bolus or subcutaneous LMWH for thrombosis prophylaxis, were determined in a first step to investigate the potential of LMWH for antithrombotic cover.

MATERIALS AND METHODS

Signs of thrombin generation (D-dimer and F1+2), anti-Xa activity and activated clotting time (ACT) were measured in 65 patients with congenital heart disease. A total of 40 patients were treated with a UFH bolus of 100 IU/kg bodyweight and, in 25 children, enoxaparin was subcutaneously administered at a dosage of 1/1.6 mg/kg bodyweight.

RESULTS

The dose to plasma activity of enoxaparin was more consistent than in the UFH group. Only a slight elevation of F1+2 was found in some patients, which was a little higher in the enoxaparin group, but no difference of incidence of increased F1+2 generation was detected between the two groups. D-dimer was elevated in three children after UFH bolus application, but no such effect was observed in any child after LMWH administration.

CONCLUSIONS

Application of LMWH was equally efficacious during pediatric cardiac catheterization than UFH bolus administration, as determined by plasma levels and markers of clotting activation. In contrast to UFH bolus, no further monitoring was necessary after the application of LMWH during cardiac catheterization due to a consistent dose to plasma activity.

Safety profile of tinzaparin administered once daily at a standard curative dose in two hundred very elderly patients

OBJECTIVES

Too few very elderly patients with an age-related renal impairment are included in clinical trials. We conducted a study in order to evaluate the safety profile of tinzaparin, a low molecular weight heparin (LMWH), given at a curative dose (175 IU/kg once daily) in very elderly patients treated for up to 30 days.

SETTING

An 800-bed geriatric hospital.

DESIGN

A 1-year prescribing study.

PATIENTS

Consecutive in-patients older than age 70, whose creatinine clearance was above 20 ml/min, and requiring full anticoagulation with LMWH were included.

MEASUREMENTS

Safety parameters (major bleeding/heparin-induced thrombocytopenia/death) were recorded. Plasma anti-Xa activity levels were regularly measured throughout the treatment period.

RESULTS

Two-hundred in-patients, mean age 85.2 +/- 6.9 years (70 to 102), mean creatinine clearance 51.2 +/- 22.9 ml/min, were given tinzaparin. Six patients died during the treatment period: only one could be related to the anticoagulation treatment. Three major bleeding episodes (1.5%) were reported. Antithrombotic drug interactions likely contributed to the bleeding event in two of them. Heparin-induced thrombocytopenia was confirmed in two patients (1%). No correlation was found between anti-Xa activity and creatinine clearance or age.

CONCLUSIONS

Tinzaparin can be used safely at a curative dose in very elderly patients as long as (i) the accurate bodyweight-adjusted dose is given; (ii) platelet counts and anti-Xa levels are regularly monitored and; (iii) the interaction with other antithrombotic drugs is correctly managed.

The low molecular weight heparin, tinzaparin, in thrombosis and beyond

Standard unfractionated heparin (UFH) has been in clinical use for over 50 years. The commercial use of low molecular weight heparins (LMWHs) began in the mid 1980s for hemodialysis and the prophylaxis of deep vein thrombosis (DVT). Initially, the clinical development of LMWHs was concentrated on the European continent. Subsequently, LMWHs were introduced in North America as well. In the initial stages of development of these drugs only nadroparin, dalteparin and enoxaparin were used. Subsequently, several other LMWHs such as ardeparin, tinzaparin, reviparin and parnaparin were introduced. LMWHs constitute a group of important medications with total sales reaching nearly 2.5 billion dollars with expanded indications reaching far beyond the initial indications for the prophylaxis of post-surgical DVT. This review highlights the pharmacology of tinzaparin. Unlike other LMWHs, tinzaparin is prepared by enzymatic hydrolysis with heparinase, while various chemical depolymerization methods are used for the synthesis of other LMWHs. As compared with the standard heparin, LMWHs have different pharmacodynamic, and pharmacokinetic properties; they also differ in clinical benefits.

Treatment and prophylaxis of venous thromboembolism during pregnancy

The treatment and prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE) in pregnant patients is challenging for several reasons. Coumarins can cause embryopathy and other adverse effects in the fetus. Although unfractionated heparin and low-molecular-weight heparins, the cornerstones of initial therapy, are safe for the fetus, they can have significant maternal side effects, including osteoporosis and thrombocytopenia. Because they must be given parenterally, long-term administration is inconvenient. Further, although low-molecular-weight heparins probably cause less maternal osteoporosis and thrombocytopenia than unfractionated heparin, the appropriate dosing regimens for prevention and treatment of thrombosis during pregnancy have not been established. In addition, there is a paucity of reliable information on the incidence of venous thromboembolism and the risk of recurrent thrombosis during pregnancy. This paper briefly reviews the areas of controversy and provides recommendations for the treatment and prophylaxis of acute deep vein thrombosis and pulmonary embolism in pregnant patients.

The hypercoagulable state of malignancy: pathogenesis and current debate

A hypercoagulable or prothrombotic state of malignancy occurs due to the ability of tumor cells to activate the coagulation system. It has been estimated that hypercoagulation accounts for a significant percentage of mortality and morbidity in cancer patients. Prothrombotic factors in cancer include the ability of tumor cells to produce and secrete procoagulant/fibrinolytic substances and inflammatory cytokines, and the physical interaction between tumor cell and blood (monocytes, platelets, neutrophils) or vascular cells. Other mechanisms of thrombus promotion in malignancy include nonspecific factors such as the generation of acute phase reactants and necrosis (i.e., inflammation), abnormal protein metabolism (i.e., paraproteinemia), and hemodynamic compromise (i.e., stasis). In addition, anticancer therapy (i.e., surgery/chemotherapy/hormone therapy) may significantly increase the risk of thromboembolic events by similar mechanisms, e.g., procoagulant release, endothelial damage, or stimulation of tissue factor production by host cells. However, not all of the mechanisms for the production of a hypercoagulable state of cancer are entirely understood. In this review, we attempt to describe what is currently accepted about the pathophysiology of the hypercoagulable state of cancer. We also discuss whether or not to screen patients with idiopathic deep venous thrombosis for an underlying malignancy, and whether this would be beneficial to patients. It is hoped that a better understanding of these mechanisms will ultimately lead to the development of more targeted treatment to prevent thromboembolic complications in cancer patients. It is also hoped that antithrombotic strategies may also have a positive effect on the process of tumor growth and dissemination.

Use of cardiovascular medications in the elderly

Cardiovascular disease is the leading cause of death in patients aged 65 and above. Although elderly persons represent only 12.4% of the US population, they account for about a third of drug expenditures. However the appropriate use of cardiovascular medications in these patients has been shown to reduce the rate of cardiovascular morbidity and mortality. The normal aging and the disease process in the elderly result in significant changes at the structural and molecular level in the elderly. The changes that take place in the autonomic nervous system, the kidneys, and the liver in the elderly modify the metabolism and clinical effects of most medications. Elderly patients are also susceptible to side effects and adverse drug reactions. Physicians should have a clear understanding of the normal aging processes, the abnormal changes due to disease process and the changes in the pharmacology of drugs in the elderly to deliver proper care to the elderly patient.

Tinzaparin

Low-molecular-weight heparins (LMWH) are efficacious agents that offer clinical and pharmacoeconomic advantages over unfractionated heparin (UFH) for the treatment of ACS and venous thromboembolism. Tinzaparin is a LMWH approved for the treatment of deep venous thrombosis with and without pulmonary embolism, when used in conjunction with warfarin. In studies with hospitalized patients who had deep venous thrombosis or pulmonary embolism, tinzaparin was at least as efficacious as UFH, with fewer adverse bleeding events. It is also efficacious for thromboembolic prophylaxis in patients undergoing general and orthopedic surgery. Studies have shown that tinzaparin is at least as effective as UFH for patients undergoing surgery and in other patients at risk for developing thromboembolism. It is currently not recommended for use in patients with ischemic strokes. There are minimal data available regarding its use in the management of patients with unstable angina (UA) and non-ST-segment elevation myocardial infarction.

High-dose tinzaparin in pregnancy and the need for urgent delivery

The prolonged anticoagulant effects of high-dose low molecular weight heparin (LMWH) pose problems in pregnant women when unanticipated delivery is required. We present two pregnant women on therapeutic doses of LMWH whose labour did not progress smoothly. The Thrombelastograph coagulation analyser was used to assess the coagulation status periodically. It influenced surgical and anaesthetic management and there was a safe outcome.

Use of low molecular weight heparin in acute venous thromboembolic events in pregnancy

OBJECTIVE

To compare the maternal and neonatal outcomes arising from the use of low molecular weight heparin (LMWH) or unfractionated heparin (UFH) in the treatment of acute venous thromboembolism (VTE) in pregnancy.

STUDY DESIGN

A retrospective review of the charts of all women treated for acute VTE in pregnancy at the Ottawa Hospital from January 1990 to December 1999.

RESULTS

Twenty-three cases were identified, of which 11 were treated with LMWH and 12 with UFH. Maternal and fetal outcomes were similar between the two groups. Hospital length of stay was shorter in the LMWH group. There was no difference in delivery management between the two groups. There was minor bleeding in 2 women in the UFH group and none in the LMWH group. There was one recurrent VTE during treatment in each of the groups.

CONCLUSION

There is no difference in complication rate between LMWH and UFH in the treatment of acute VTE in pregnancy.

Outpatient management of DVT using low molecular weight heparin and a hospital outreach service

In recent years there have been several studies comparing the efficacy and safety of low molecular weight (LMW) and unfractionated heparin for the treatment of deep venous thrombosis (DVT), showing them in the clinical trial setting to be equal in these regards. LMWH has the advantage of once daily subcutaneous injection and daily monitoring of levels is not usually required. This has led many centres to develop outpatient treatment strategies for these patients but evidence for the safety of this approach is scarce. In 1997 we developed a hospital outreach service for the treatment of patients with DVT and, in a retrospective study, have compared the outcome in 172 patients treated at home with 172 age, sex and thrombotic risk factor matched inpatients treated at our institution with unfractionated heparin. Five patients in the home treatment group suffered a haemorrhagic event, compared with six patients in the hospital group. One patient in the home treatment group had a recurrent DVT within the first 3 months of treatment; in the hospital-treated group, six patients had recurrent DVTs and nine developed pulmonary emboli. At 3 months, there were three deaths in the home treatment group, compared with five deaths in the hospital group. There was no difference in re-admission rate at 3 months: 23 in the home treatment group, 24 in the hospital-treated group. Average length of hospital stay for the home-treatment group was 2.1 days and 12 days for the hospital group. Warfarin control was found to be significantly better in those patients treated at home, and only 18% of patients treated in hospital received heparin according to hospital guidelines. In conclusion, outpatient management of patients with DVT using LMWH is as safe as hospitalization and continuous infusion of unfractionated heparin. The complication rate was lower in the home treatment group and, in particular, the incidence of recurrent thrombosis was significantly less in the home treatment group. In addition, warfarin control was better when managed by specialist nurses. Patients expressed a preference for home treatment.

[Outpatient treatment of acute deep venous thrombosis of the lower limbs]

The outpatient management of acute deep vein thrombosis could replace the inpatient care for most patients. Fixed-dose, weight-adjusted low-molecular-weight heparins, as efficacious and safe as unfractionated heparin, allow home treatment for selected and eligible patients. The main exclusion criteria are severe renal insufficiency, high risk of bleeding, pulmonary embolism with unstable hemodynamics, allergy to heparin and suspected non-compliance. Programs for outpatient management need, after appropriate selection, adequate patient education, easy access to health-care professionals and daily follow-up during heparin treatment.

Recent advances in pulmonary embolism diagnosis and management

Pulmonary embolism remains a major problem in clinical practice. Pulmonary angiography remains the most accurate diagnostic procedure. Standard therapy includes heparin then warfarin, and now low molecular weight heparin. The role of prophylactic measures cannot be over emphasized.

The role of the advanced practice nurse in anticoagulation

The advanced practice nurse is uniquely qualified to act as a consultant and specialist in the field of anticoagulation at an acute care hospital. The advanced practice nurse acts at both a system level and a patient care level to improve anticoagulation with low-molecular-weight heparins, heparin, and warfarin through education, research, quality improvement initiatives, and patient care management.

Pulmonary embolism

Pulmonary embolism (PE) is a common problem for which prompt diagnosis and treatment is essential to minimize mortality. The clinical presentation is more variable than sudden dyspnea and chest pain, especially in the critical care patient. Recognition of venous thromboembolic (VTE) risk factors can help develop a good clinical suspicion for PE. A wide range of diagnostic tests are available to the clinician. The ventilation/perfusion scan, pulmonary arteriogram, and lower extremity investigations are still important for diagnosis. Other noninvasive tests such as spiral CT with venography, echocardiography, and D-dimers are becoming more accepted. Heparin is the mainstay of PE therapy, but thrombolytic treatment may be lifesaving in the unstable patient. VTE prophylaxis should be considered in all post-operative or critical care patients.

Randomized trial of different regimens of heparins and in vivo thrombin generation in acute deep vein thrombosis

Low-molecular-weight and unfractionated heparins are frequently used to treat venous thromboembolism, but it is not known whether they are equally effective in inhibiting in vivo generation of thrombin. In this multicenter trial, 1048 patients were randomized to intravenous unfractionated heparin (group A), twice daily low-molecular-weight heparin (reviparin) for 1 week (group B), or once daily reviparin for 4 weeks (group C). All patients received vitamin K antagonists. Blood samples withdrawn at the baseline and at weeks 1 and 3 were analyzed using markers of in vivo thrombin generation and other coagulation parameters. During the first 3 weeks symptomatic recurrent deep vein thrombosis-pulmonary embolism (DVT/PE) occurred in 17 (4.5%) of 375 patients in group A compared with 4 (1.0%) of 388 patients in group B, and 9 (2.4%) of 374 patients in group C. Forty percent of patients in group A, 53.4% in group B, and 53.5% in group C showed 30% or greater reduction in thrombus size assessed by venography. Patients in group B had significantly greater reduction in D-dimer, prothrombin fragments 1 and 2 (F1 + 2), endogenous thrombin potential (ETP), and thrombin-antithrombin (TAT) complexes compared to groups A and C. Greater release of tissue factor pathway inhibitor (TFPI) and reduction in levels of thrombin activatable fibrinolysis inhibitor (TAFI) and fibrinogen were significantly more pronounced in group C patients. Reviparin administered twice daily plus vitamin K antagonist is more effective in inhibiting in vivo thrombin generation compared to intravenous unfractionated heparin plus vitamin K antagonist, and reviparin once daily produced significantly higher TFPI release and greater reduction in TAFI and fibrinogen levels.

The pharmacodynamics of tinzaparin in healthy volunteers

We report the pharmacodynamic properties of tinzaparin (175 U/kg antifactor Xa) given as a single daily administration for 5 consecutive days to 14 healthy volunteers as a known safe, effective treatment of deep vein thrombosis and pulmonary embolism. The Cmax for antifactor Xa (0.87 +/- 0.15 U/ml) was associated with a 2.4 +/- 0.5-fold prolongation of the activated partial thromboplastin time (APTT) and a high antithrombin activity (0.38 +/- 0.1 U/ml). The Cmax value of antifactor Xa was 1.5- and twofold lower than those generated by similar doses of nadroparin and enoxaparin respectively. The clearance of antifactor Xa activity (1.29 +/- 0.2 l/h) was 1.5- and twofold greater than those reported for nadroparin and enoxaparin respectively. These results indicated that the antithrombotic and prohaemorrhagic effects of a low molecular weight heparin were independent from the absolute levels of antifactor Xa activities and from the prolongation of the APTT.

Cost effectiveness of tinzaparin sodium versus unfractionated heparin in the treatment of proximal deep vein thrombosis

OBJECTIVE

To evaluate economic and health implications of tinzaparin sodium, a once a day low-molecular-weight heparin (LMWH), versus unfractionated heparin (UFH) in the treatment of acute deep vein thrombosis (DVT) from a US healthcare payer perspective.

STUDY DESIGN

An economic model, composed of two submodules, was created: A short-term module based on clinical trial data covering the first 3 months and a long-term module that projects trial results based on published data for up to 50 years.

METHODS

Clinical trial results were combined with data from long-term follow-up studies of DVT in a model that estimates the health and economic consequences of treatment. Both short- and long-term costs with tinzaparin sodium were compared with UFH, as were health outcomes and quality-adjusted life-years (QALYs).

RESULTS

Patients treated with tinzaparin sodium are estimated to live a mean of 0.9 years longer on average (0.6 discounted), resulting in an increase of 0.8 QALYs (0.5 discounted). At the same time, lifetime savings are US dollars 621 per patient (1999 values), even when all patients receiving tinzapirin sodium are treated as inpatients. Early discharge of patients receiving tinzaparin sodium, or outpatient treatment, would save between US dollars 3000 and US dollars 5000 per patient.

CONCLUSION

Tinzaparin sodium leads to better health outcomes and substantial economic savings compared with UFH treatment when all management costs are considered.

Low molecular weight heparin and unfractionated heparin in the early pharmacologic management of acute coronary syndromes: a meta-analysis of randomized clinical trials

BACKGROUND

The standard of care in Acute Coronary Syndromes (ACS) includes a full complement of antischemic and antithrombotic therapy. Although aspirin is used widely and concomitant anticoagulation is recommended, the comparative benefits of low molecular weight heparin (LMWH) and unfractionated heparin (UFH) have not been defined.

METHODS/RESULTS

A meta-analysis including all randomized clinical trials comparing LMWH and UFH for the treatment of non-ST segment elevation acute coronary syndromes was performed. Risk ratios (RR), using the DerSimonian-Laird Model, were calculated from a total of 13,320 patients. Death (RR 0.98, 95% CI 0.73-1.31), death and myocardial infarction (MI) (RR 0.86, 95% CI 0.74-1.01), death, MI, recurrent angina or revascularization (RR 0.89, 95% CI 0.74-1.07) and major hemorrhage (RR 1.01, 95% CI 0.81-1.25) occurred with similar frequencies for the anticoagulant-based strategies.

CONCLUSIONS

Fixed dose LMWH therapy given subcutaneously compares favorably with UFH titrated to a target level of anticoagulation and should be considered a safe, effective, and clinically acceptable alternative in the early management of patients with non-ST segment elevation ACS. The superiority of LMWH preparations characterized by high in vitro factor Xa to thrombin inhibitory capacity is supported by clinic trial data but requires further investigation.

Treating venous thromboembolism: enoxaparin

This article reviews the developments that have occurred in the treatment of venous thromboembolism during the last decade, with emphasis on the establishment of low molecular weight heparin as a therapeutic agent of proven efficacy and examines the evidence that supports the movement from inpatient to outpatient hospital management of venous thromboembolism.

Pharmacology of low molecular weight heparins

Although intravenous heparin has been the treatment of choice for acute VTE disease, LMWHs are gaining wider recognition and support as not only a new option but also as the standard of care. Each LMWH is viewed as a unique drug by regulatory agencies because of their differing physical and pharmacokinetic attributes. LMWHs have high absorption, high bioavailability, and long half-lives enabling once- or twice-daily dosing with predictable dose-response relationships. These factors enable the LMWHs to be used without laboratory monitoring and at home for acute DVT management. Studies continue to show that LMWH preparations are as at least as effective as heparin in a variety of settings, including VTE disease prophylaxis, management of acute VTE disease, unstable angina, and NSTEMI. They are at least as safe as heparin relative to hemorrhagic complications. Heparin-induced thrombocytopenia is less of a problem with LMWHs. Use of LMWHs has resulted in cost benefits in the treatment of acute DVT, unstable angina, and NSTEMI as well as in prophylaxis against venous thromboembolism. Emergency physicians, because of their unique position at the forefront of acute care, will soon regularly use LMWHs.

The outcome of ambulatory DVT management using a multidisciplinary approach

Low molecular weight heparins (LMWHs) have been demonstrated to be at least as safe and effective as unfractionated heparin (UFH) in the initial management of deep vein thrombosis (DVT). However, the effectiveness of using LMWH in the ambulatory management of DVT in a 'real-life' setting has yet to be evaluated. This multicentre retrospective study involving 697 patients considers the outcome data of patients under- going ambulatory DVT treatment with tinzaparin (Innohep(R), Leo Pharmaceuticals, Risborough, Buckinghamshire, UK). During the 6 months following presentation, 17 (2.5%) patients had confirmed thromboembolic complications, of which 14 occurred subsequent to the initial LMWH treatment phase ('late'). There were no deaths in this group. Bleeding complications were reported in 23 (3.4%) patients, with 13 of these being classified as 'late'. Of these, two events were considered major resulting in hospitalization and death. Hospitalization for all causes was 6.8% (45 patients) with 32 patients being admitted for thromboembolic or bleeding complications. Overall mortality was 6.7%. These results compare favourably with published clinical trial data. This study demonstrates that ambulatory treatment of proven DVT with LMWH is both safe and effective.

Orally active heparin and low-molecular-weight heparin

The heparins, (unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH)) given by subcutaneous or intravenous injection have been used extensively in the prevention and treatment of both venous and arterial thromboembolic disorders. The increasing use of the heparins, LMWHs in particular, in the out of hospital setting has stimulated interest in the development of orally absorbable antithrombotic agents that require little or no monitoring, and this includes the heparins. UFH or LMWH delivered orally has been shown to have an antithrombotic effect in animal thrombosis models although there is little change in plasma coagulation tests. The addition of a simple organic chemical N -(8-(2-hydroxybenzoyl)amino)caprylate (SNAC) to UFH markedly enhances its absorption. A phase II study in patients undergoing total hip replacement indicated that SNAC heparin in two different doses was as effective and safe as UFH given subcutaneously. A phase III clinical trial comparing two doses of SNAC heparin given orally with LMWH by subcutaneous injection for the prevention of venous thromboembolism in patients undergoing total hip replacement is currently underway.

Tinzaparin in acute ischaemic stroke (TAIST): a randomised aspirin-controlled trial

BACKGROUND

Low-molecular-weight heparins and heparinoids are superior to unfractionated heparin in the prevention and treatment of venous thromboembolism, but their safety and efficacy in acute ischaemic stroke are inadequately defined.

METHODS

This randomised, double-blind, aspirin-controlled trial tested the safety and efficacy of treatment with high-dose tinzaparin (175 anti-Xa IU/kg daily; 487 patients), medium-dose tinzaparin (100 anti-Xa IU/kg daily; 508 patients), or aspirin (300 mg daily; 491 patients) started within 48 h of acute ischaemic stroke and given for up to 10 days. Primary intracerebral haemorrhage was excluded by computed tomography. Outcome was assessed, with treatment allocation concealed, by the modified Rankin scale at 6 months (independence [scores 0-2] vs dependence or death [scores 3-6]).

FINDINGS

Of 1486 randomised patients, two did not receive treatment and 46 were lost to follow-up. The proportions independent at 6 months were similar in the groups assigned high-dose tinzaparin (194/468 [41.5%]), medium-dose tinzaparin (206/486 [42.4%]), or aspirin (205/482 [42.5%]). There was no difference in effect in any predefined subgroup, including patients with presumed cardioembolic stroke. Other outcome measures were similar between the treatment groups (disability, case-fatality, and neurological deterioration rates). During the in-hospital treatment period no patient assigned high-dose tinzaparin developed a symptomatic deep-vein thrombosis compared with nine assigned aspirin. Conversely, seven patients assigned high-dose tinzaparin developed symptomatic intracerebral haemorrhage compared with one in the aspirin group.

INTERPRETATION

Treatment with tinzaparin, at high or medium dose, within 48 h of acute ischaemic stroke did not improve functional outcome compared with aspirin. Although high-dose tinzaparin was superior in preventing deep-vein thrombosis, it was associated with a higher rate of symptomatic intracranial haemorrhage.

Outpatient treatment of patients with deep-vein thrombosis or pulmonary embolism

There have been a large number of randomized trials comparing standard unfractionated intravenous heparin with low-molecular-weight heparin for the treatment of deep-vein thrombosis, but only two of these have looked at outpatient therapy. There have been only two randomized trials including patients with symptomatic pulmonary embolism, and neither of these provided outpatient therapy. Postmortem and clinical studies have shown a strong association between pulmonary embolism and the presence of venous thrombosis in the lower limbs. Based on similar rates of venous thromboembolic recurrence and death, these studies suggest that initial treatment should be the same for deep-vein thrombosis and pulmonary embolism. The feasibility of providing outpatient care to many patients seeking treatment for deep-vein thrombosis or acute pulmonary embolism at certain tertiary care hospitals has become evident, but the data suggest that the proportion of eligible patients is institution dependent and may vary from 18% to 91%. In the author's institution, approximately 50% of patients with pulmonary embolism could be treated as outpatients, but there have been no other reports on outpatient therapy for patients with pulmonary embolism. If patients with pulmonary embolism meet criteria demonstrated to result in a higher risk of death, it is, of course, reasonable to not treat such patients on an outpatient basis. Low-molecular-weight heparin followed by oral anticoagulant therapy provides adequate therapy in most patients with deep-vein thrombosis or pulmonary embolism, and many patients can be treated as outpatients.

Clinical experiences with low-molecular weight heparins in pediatric patients

The courses of 79 children (2 weeks to 19 years old) treated with two different low-molecular weight heparins (LMWHs)--nadroparin (n=66) and enoxaparin (n=13)--were retrospectively analysed. In 62 patients, LMWHs were given for short-term prophylaxis (1-2 weeks) during immobilization after surgery or trauma. Thirteen children with thromboembolic events received long-term prophylaxis with LMWHs for 2-18 months--six after thrombolytic therapy and seven after therapy with unfractionated heparin (UFH). Because of thromboembolic events, four patients were initially treated with LMWHs. In all patients with short-term prophylaxis, no thrombosis occurred. After thrombolytic therapy, three children had no reocclusion, two had no thrombus apposition and one had complete recanalization. In the seven patients treated with LMWHs after UFH, four had no reocclusion, two had recanalization and one had reocclusion. In all patients receiving LMWHs for initial treatment of thrombosis, no thrombus apposition, but also no recanalization, occurred. For short-term prophylaxis, nadroparin was used independent of the body weight and without determination of anti-factor Xa (anti-FXa) activity. Long-term prophylaxis was given mainly as doses of 45-100 anti-FXa U/kg resulting in anti-FXa activities between 0.2 and 0.4 U/ml. For treatment of thrombosis, doses of 200-300 anti-FXa U/kg corresponded to 0.5-1.0 anti-FXa U/ml. Side effects--slight gastrointestinal bleeding and temporary reversible hair loss--were seen in two patients. In conclusion, LMWHs proved to be efficacious and safe especially in prophylaxis of thromboembolic events in children.