Low-molecular-weight heparins in the treatment of deep-vein thrombosis

A Literature Review of the Potential Impact of Medication on Vitamin D Status

In recent years, there has been a significant increase in media coverage of the putative actions of vitamin D as well as the possible health benefits that supplementation might deliver. However, the potential effect that medications may have on the vitamin D status is rarely taken into consideration. This literature review was undertaken to assess the degree to which vitamin D status may be affected by medication. Electronic databases were searched to identify literature relating to this subject, and study characteristics and conclusions were scrutinized for evidence of potential associations. The following groups of drugs were identified in one or more studies to affect vitamin D status in some way: anti-epileptics, laxatives, metformin, loop diuretics, angiotensin-converting enzyme inhibitors, thiazide diuretics, statins, calcium channel blockers, antagonists of vitamin K, platelet aggregation inhibitors, digoxin, potassium-sparing diuretics, benzodiazepines, antidepressants, proton pump inhibitors, histamine H2-receptor antagonists, bile acid sequestrants, corticosteroids, antimicrobials, sulphonamides and urea derivatives, lipase inhibitors, hydroxychloroquine, highly active antiretroviral agents, and certain chemotherapeutic agents. Given that the quality of the data is heterogeneous, newer, more robustly designed studies are required to better define likely interactions between vitamin D and medications. This is especially so for cytochrome P450 3A4 enzyme (CYP3A4)-metabolized medications. Nevertheless, this review suggests that providers of health care ought to be alert to the potential of vitamin D depletions induced by medications, especially in elderly people exposed to multiple-drug therapy, and to provide supplementation if required.

The Effect of Low Molecular Weight Heparins on Fracture Healing

Venous Thromboembolism is a serious complication in the trauma patient. The most commonly studied and used anticoagulant treatment in prophylaxis of thrombosis is heparin. The prolonged use of unfractionated heparin has been connected with increased incidence of osteoporotic fractures. Low molecular-weight-heparins (LMWHs) have been the golden rule in antithrombotic therapy during the previous two decades as a way to overcome the major drawbacks of unfractioned heparin. However there are few studies reporting the effects of LMWHs on bone repair after fractures. This review presents the studies about the effects of LMWHs on bone biology (bone cells and bone metabolism) and underlying the mechanisms by which LMWHs may impair fracture healing process. The authors' research based on literature concluded that there are no facts and statistics for the role of LMWHs on fracture healing process in humans and the main body of evidence of their role comes from in vitro and animal studies. Further large clinical studies designed to compare different types of LMWHs, in different dosages and in different patient or animal models are needed for exploring the effects of LMWHs on fracture healing process.

Are therapeutic decisions made on the medical admissions unit any more evidence-based than they used to be?

RATIONALE, AIMS AND OBJECTIVES

To determine whether inpatients in a medical admissions unit in a UK district general hospital received evidence-based therapies in 2008.

METHODS

The diagnoses of and therapies received by inpatients at the George Eliot Hospital National Health Service Trust in Nuneaton were recorded. A clinical librarian searched the literature (Clinical Knowledge Summaries, Cochrane Library, Medline and Embase) for the best evidence for each diagnosis-therapy pair. Evidence was graded on the following scale: systematic review, randomized controlled trial, non-experimental evidence and no or contrary evidence.

RESULTS

One hundred and two patients generated 150 diagnosis-therapy pairs. Of these 61 (41%) had systematic review level evidence supporting them, 17 (11%) randomized controlled trial evidence, 48 (32%) non-experimental evidence and 24 (16%) no evidence.

CONCLUSIONS

Results were comparable with previous studies. Care in a medical admissions unit in 2008 is still evidence-based, but, despite the vast growth in medical literature, no more than it was. The process was a useful collaboration between medical and library staff to audit the quality of patient care.

A case of warfarin skin necrosis despite enoxaparin anticoagulation in a patient with protein S deficiency

Warfarin-induced skin necrosis is a rare complication associated with the use of oral anticoagulants. Most patients develop this at the initiation of therapy, often while still receiving intravenous unfractionated heparin (UFH). Recently, low-molecular-weight heparins (LMWHs) have gained wider use, providing an option for outpatient treatment of deep-vein thrombosis. The treatment protocols are similar to UFH, including the early initiation of oral anticoagulation with warfarin. A Medline search failed to reveal any cases of warfarin-induced skin necrosis while using a LMWH. We present a patient with protein S deficiency who developed warfarin skin necrosis despite appropriate anticoagulation with enoxaparin, and review the chemical and clinical difference between UFH and LMWH.

Epidural blood patch in a patient taking enoxaparin

A 36-year-old, 204-kg parturient with a past medical history of Factor V Leiden requiring enoxaparin therapy developed a postdural puncture headache. With careful coordination of her enoxaparin dosing, an epidural blood patch was successfully performed. Performance of a blood patch in patients taking enoxaparin involves the withholding of the medication for a specific period.

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.

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.

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.

Assessment of the stability of dalteparin sodium in prepared syringes for up to thirty days: an in vitro study

BACKGROUND

If a low-molecular-weight heparin (LMWH) injectable formulation maintains its stability for up to 30 days, substantial cost reductions in hospital stay could be achieved with its use on an outpatient basis in patients who might otherwise be treated with IV heparin as inpatients.

OBJECTIVE

This study was designed to assess the stability for up to 30 days of injectable solutions of the LMWH dalteparin sodium when repackaged in plastic syringes.

METHODS

In the first part of the study, 1-mL and 3-mL plastic syringes were filled with the contents of a 10,000-IU/mL dalteparin ampule or a 25,000-IU/mL dalteparin multidose vial. In a separate part of the study, 1-mL and 3-mL syringes were filled with doses of 7500 IU and 10,000 IU, respectively, from a 10,000-IU/mL multidose vial. After the syringes were brought to room temperature or 4 degrees C, the stability of dalteparin was assessed over 30 days by measuring anti-factor Xa levels.

RESULTS

No significant loss of dalteparin activity was found for up to 30 days in the syringes after storage at room temperature or 4 degrees C. The solutions retained anti-factor Xa activity at room temperature and under refrigeration.

CONCLUSION

Dalteparin is stable for up to 30 days when stored at room temperature or 4 degrees C. The findings suggest that preparation of a postdischarge supply of dalteparin is feasible, contributing to more convenient and effective management of outpatients at risk for thrombotic complications.

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.

Development of new heparin-like compounds and other antithrombotic drugs and their interaction with vascular endothelial cells

The anticlotting and antithrombotic activities of heparin, heparan sulfate, low molecular weight heparins, heparin and heparin-like compounds from various sources used in clinical practice or under development are briefly reviewed. Heparin isolated from shrimp mimics the pharmacological activities of low molecular weight heparins. A heparan sulfate from Artemia franciscana and a dermatan sulfate from tuna fish show a potent heparin cofactor II activity. A heparan sulfate derived from bovine pancreas has a potent antithrombotic activity in an arterial and venous thrombosis model with a negligible activity upon the serine proteases of the coagulation cascade. It is suggested that the antithrombotic activity of heparin and other antithrombotic agents is due at least in part to their action on endothelial cells stimulating the synthesis of an antithrombotic heparan sulfate.

Does prior administration of enoxaparin influence the effects of levobupivacaine on blood clotting? Assessment using the Thrombelastograph

The low molecular weight heparin, enoxaparin (by inhibition of factors Xa and IIa) and amide local anaesthetics (by altering platelet function) exert anti-clotting effects. Although these agents are often used in combination during the perioperative period, their potential interactive effect on clotting has not been defined. Blood from 10 ASA I-II patients who received enoxaparin 0.5 mg kg(-1) s.c. was studied using a Thrombelastograph (TEG) either alone or in combination with levobupivacaine (2.5 mg ml(-1) or 2.5 microg ml(-1)) or saline (50% dilution). In blood from patients who had received enoxaparin 0.5 mg kg(-1) s.c. 12 h previously, levobupivacaine 2.5 mg ml(-1) (but not 2.5 microg ml(-1)) produced significant changes in TEG clotting parameters (mean (SD) 15.7 (4.8) mm, 29.6 (25.6) mm, 34.4 (14.6) mm, 34.3 (12.2) degrees compared with control values of 6.1 (1.3) mm, 2.5 (0.5) mm, 63.5 (6.4) mm and 74.1 (2.9) degrees for r, K, MA, and alpha angle respectively).

Venous thromboembolism in the intensive care unit

Venous thromboembolic disease has emerged as a significant cause of morbidity and mortality in hospitalized patients. This article reviews the salient features of venous thromboembolism as they pertain to the critically ill. Emphasis is placed on identifying risk factors, diagnostic strategies, prophylaxis, and treatment of this disorder. Deep venous thrombosis and pulmonary embolism, both being manifestations of the same disease processes, are considered together in this discussion of venous thromboembolism.