Antithrombotic therapy and pregnancy: consensus report and recommendations for prevention and treatment of venous thromboembolism and adverse pregnancy outcomes

Venous thromboembolism and adverse pregnancy outcomes are potential complications of pregnancy. Numerous studies have evaluated both the risk factors for and the prevention and management of these outcomes in pregnant patients. This consensus group was convened to provide concise recommendations, based on the currently available literature, regarding the use of antithrombotic therapy in pregnant patients at risk for venous thromboembolic events and adverse pregnancy outcomes.

Warfarin and its interactions with foods, herbs and other dietary supplements

Despite its complex pharmacokinetic and pharmacodynamic profile, warfarin is still one of the most widely used oral anticoagulant agents. Attaining optimal anticoagulation with this agent is clinically challenging in view of its many food and drug interactions. Inappropriate anticoagulation control can expose patients to an increased risk of bleeding or thromboembolic complications, due to over and underanticoagulation, respectively. Fluctuations in dietary vitamin K intake can have a significant effect on the degree of anticoagulation in patients treated with warfarin. In addition, the explosion in use of various dietary supplements and herbal products can lead to undesired outcomes on anticoagulant levels. The aim of this review is to discuss the scope and the potential clinical impact of the most commonly reported food, dietary supplement and herbal interactions with warfarin therapy. Practical steps for patients and providers to minimise these interactions are highlighted.

Examining Differences in Weekly Warfarin Dose in Patients With and Without Cancer

The incidence of thrombosis and bleeding is higher in patients with cancer receiving warfarin compared with low molecular weight heparins. Despite these findings, warfarin remains a commonly used treatment strategy for anticoagulation in patients with cancer secondary to several factors that limit the use of low molecular weight heparins. Determining the appropriate warfarin dose in cancer patients is challenging. The objective of our study is to compare the weekly warfarin dose in patients with and without cancer. In a retrospective analysis, the average weekly warfarin dose was compared for 63 subjects who 1) were treated for cancer while receiving warfarin (n = 21), 2) completed treatment for their cancer before starting warfarin (n = 21), and 3) received warfarin with no diagnosis of cancer (n = 21). The data were abstracted from the medical record from the date the subject started taking a stable dose of warfarin after the initial titration until the discontinuation of warfarin. No significant differences were observed in the mean weekly warfarin dose, but the dose demonstrated greater intrasubject variability for subjects in group 1 (group 1, 31 +/- 22% vs. 2, 19 +/- 11% and 3, 15 +/- 10%, P = 0.003). Subjects in group 1 also spent more time above their goal International Normalized Ratio (group 1, 30 +/- 21% vs. 2, 21 +/- 16% and 3, 15 +/- 16%, P = 0.038). The average weekly warfarin dose was similar for the three groups, but the results of this study suggest that patients with cancer receiving treatment for their cancer and anticoagulation with warfarin are more difficult to appropriately anticoagulate.

Antiplatelet Therapy in Patients with Unstable Angina and Non–ST-Segment-Elevation Myocardial Infarction: Findings from the CRUSADE National Quality Improvement Initiative

Evidence-based clinical practice guidelines encapsulate current knowledge to guide health care professionals in the treatment of patients with unstable angina or non-ST-segment-elevation myocardial infarction (NSTEMI), yet adherence to guideline recommendations is suboptimal. Guideline adherence may be improved by quality improvement programs such as the CRUSADE (Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation?) National Quality Improvement Initiative of the American College of Cardiology-American Heart Association Guidelines. The CRUSADE data have been analyzed to demonstrate that overall guideline adherence is directly associated with mortality and that improvement in guideline adherence saves lives. Also, the CRUSADE data have determined that the real-life mortality risk associated with unstable angina and NSTEMI is greater than suggested by clinical trials. The newer antiplatelet drugs recommended in early intervention and discharge treatment strategies are underused across many segments of the unstable angina-NSTEMI population. Glycoprotein IIb-IIIa inhibitors are underused in high-risk populations, and clopidogrel is markedly underused in patients who are medically managed rather than undergoing percutaneous coronary intervention or coronary artery bypass graft surgery. In addition, often the specialty of the treating physician and the status of the hospital influence the use of antiplatelet therapy. The reasons for underprescribing of antiplatelet drugs by physicians are not entirely clear but may be related to a lack of guideline familiarity and understanding, as well as factors such as drug novelty, safety, and cost. Continued education and data dissemination are therefore vital in promoting the prescription of guideline-recommended drugs, both in the early hospitalization phase and as patients transition to community-based care. The role of the pharmacist is pivotal in ensuring adherence to clinical guidelines by interacting with both the physician and patient.

Low-molecular-weight heparin in pregnancy: peripartum bleeding complications

OBJECTIVE

To compare bleeding complications in pregnant patients treated with low-molecular-weight heparin (LMWH) to untreated controls.

STUDY DESIGN

A case-control study of patients from 2001 to 2005 who received prophylactic or therapeutic doses of LMWH during pregnancy was carried out. Indications for LMWH included current or prior thromboembolism, thrombophilia, or heart valve replacement. Controls were chosen in a 2:1 ratio to cases, matched for delivery route, and selected as the next two consecutive deliveries. The primary outcome was postpartum hemorrhage (PPH). Odds ratios (ORs) were calculated with 95% confidence intervals (CIs).

RESULTS

Forty-nine women treated with LMWH delivered 55 infants. Current or prior thromboembolic disease was the anticoagulation indication in 15/55 (27.3%) and 26/55 (47%) of pregnancies, respectively. There were more obese gravidas (OR 3.91, CI 1.70 to 9.09) and labor induction was more common in the LMWH group, 25/55 (45%) vs 29/110 (26%), P=0.01. There was no difference in estimated blood loss (295.7+/-145.7 vs 308.6+/-111.9 cm(3), P=0.62 vaginal; 687.5+/-251.8 vs 765.0+/-313.2 cm(3), P=0.34 cesarean), PPH (6/55, 11% vs 9/110, 8.2% OR 1.37, CI 0.16 to 11.5) or transfusion (3/55, 5.4% vs 4/110, 3.6% OR 1.50, CI 0.3 to 7.48) between the cases and controls. There were two cases of postpartum pulmonary emboli, one with a maternal mortality.

CONCLUSION

Bleeding complications, including PPH and transfusion, in patients treated with LMWH during pregnancy were not increased when compared to normal controls matched for delivery route.

Assessing, preventing, and treating venous thromboembolism: Evidence-based approaches

PURPOSE

The long-term complications of deep vein thrombosis (DVT), assessment of risk for venous thromboembolism (VTE) in medical and surgical patients, recommendations in evidence-based guidelines for VTE prophylaxis in surgical and medical patients and the treatment of VTE, and a new alternative for VTE prophylaxis and treatment are discussed.

SUMMARY

Pulmonary embolism (PE) is an acute complication of DVT, and recurrent DVT, post-thrombotic syndrome, and death are long-term complications of DVT. The need to assess VTE risk and provide VTE prophylaxis are well recognized in surgical patients. However, VTE prophylaxis is underutilized in medical patients despite the fact that DVT is common and guidelines for prophylaxis are available, partly because the condition often is asymptomatic in these patients. The risk for VTE increases as the number of risk factors increases, so the aggressiveness of VTE prophylaxis in medical and surgical patients increases as the risk of VTE increases. The most recent American College of Chest Physicians (ACCP) guidelines recommend low-dose unfractionated heparin or low-molecular-weight heparin (LMWH) for VTE prophylaxis in acutely ill medical patients. The treatment of VTE recommended by ACCP involves short-term LMWH or unfractionated heparin therapy plus long-term oral warfarin therapy. The pentasaccharide, factor Xa inhibitor, fondaparinux is a new alternative for VTE prophylaxis and treatment. Reducing LMWH doses for patients with severe renal impairment may offer a safety advantage. Fixed doses of LMWH are customarily used for VTE prophylaxis regardless of body weight or body mass index, but weight-based dosing with larger doses for obese patients may be more effective than fixed doses.

CONCLUSION

Efforts to assess VTE risk and apply evidence-based guidelines for VTE prophylaxis and treatment in medical patients as well as surgical patients can improve patient care and outcomes. Findings from recent clinical research provide clinicians with clarification about the optimal prophylactic and treatment strategies, and future guidelines will reflect these findings.

Survey of hospitals for guidelines, policies, and protocols for anticoagulants

PURPOSE

A survey of community hospitals that are part of a national group purchasing organization (GPO) was conducted to assess the formulary status of currently available anticoagulants, assess the current status of anticoagulant prescribing guidelines and the existing scope of such guidelines, and identify perceptions about the appropriateness of the use of anticoagulants in community hospitals in the United States.

METHODS

A Web-based survey of acute care hospitals that were members of a leading health care resource management and GPO was conducted. The survey was sent to 224 hospitals.

RESULTS

Of 224 hospitals, 127 participated in the survey, a response rate of 59.6%. Warfarin, unfractionated heparin (UFH), and enoxaparin were the anticoagulants most commonly included (>80%) on the hospitals' drug formularies. Guidelines relating to the use of UFH and low-molecular-weight heparins (LMWHs) existed in approximately 87.4% and 55.1% of responding hospitals, respectively, followed by warfarin and direct thrombin inhibitors (DTIs) (approximately 44.1% and 30.7%, respectively). Among hospitals without guidelines, 78.2%, 72.1%, 65.4%, 50.0%, and 41.4% reported that such guidelines would be useful if they included LMWHs, warfarin, DTIs, UFH, and fondaparinux, respectively. Guidelines for prophylaxis of venous thromboembolism (VTE), appropriate drug selection, and dosing for VTE prophylaxis and treatment existed in 59.8%, 53.5%, and 43.3% of the hospitals, respectively.

CONCLUSION

The study found that a sizable percentage of the responding community hospitals did not have guidelines, protocols, or policies related to the use of anticoagulants. Further, those hospitals without such guidelines commonly reported a need for clinical practice guidelines.

Basic terminology in obtaining reimbursement for pharmacists’ cognitive services

PURPOSE

A basic overview and definitions of commonly used billing and reimbursement terminology that pharmacists will need to know to obtain reimbursement for cognitive services are provided.

SUMMARY

Currently, the profession of pharmacy has been gathering momentum in its efforts to seek and obtain reimbursement for cognitive services. However, there have been major barriers in seeking reimbursement, including the lack of understanding by third-party payers of the pharmacist's role in patient care and the pharmacist's in-depth knowledge of pharmacotherapy, the lack of appropriate billing codes for pharmacists' services, and the lack of detailed knowledge and understanding by pharmacy practitioners of nondistributive reimbursement mechanisms, processes, and terminology. The types of services provided are usually described by the American Medical Association's Current Procedural Terminology (CPT) codes for the face-to-face provision of patient care services by a pharmacist. As of January 1, 2006, pharmacists have been able to indicate the appropriate diagnosis code from the International Classification of Diseases, 9th Revision (ICD-9) (ICD-10 will replace the ICD-9 on October 1, 2007), and CPT code when billing under a major medical plan that recognizes the pharmacist as a patient care service provider. Understanding the billing and reimbursement terminology will aid pharmacist communication with third-party payers, Medicare, and Medicaid. A glossary of the most commonly encountered terms in billing and reimbursement procedures for cognitive services is provided. Also included are lists of Web-based reimbursement resources and references on reimbursement for cognitive services by the pharmacist.

CONCLUSION

An understanding of terminology is important in receiving reimbursement for cognitive services.

Drug evaluation: the directly activated Factor Xa inhibitor otamixaban

Otamixaban, under development by sanofi-aventis, is a directly activated Factor X (FXa) inhibitor that is currently in phase IIb clinical trials for acute coronary syndrome and myocardial infarction. Preclinical studies with otamixaban demonstrated high selectivity of the compound for FXa. Otamixaban effectively inhibited thrombin generation without interfering with existing thrombin activity. Intravenously administered otamixaban was well tolerated in both male and female patients, independent of age. Otamixaban exhibited a well-described dose-exposure relationship, a low inter-patient variability in plasma exposure, and was both rapidly distributed in the plasma and quickly eliminated. The rapid decrease in otamixaban plasma concentrations following the termination of an infusion is an advantage over other FXa inhibitors that have longer half-lives. Otamixaban exhibited an improved pharmacodynamic profile over conventional anticoagulant therapies such as heparin. During clinical trials with otamixaban, no major drug interactions were observed with agents that were likely to be used in combination therapy. Otamixaban is a promising agent that merits further consideration for clinical trials in patients with coronary thrombosis.

Easing the economic burden of acute coronary syndromes: cost-effectiveness of emerging therapies

Although only part of the entire treatment regimen, antithrombotic therapy represents a large portion of the total costs associated with acute coronary syndromes (ACS) treatment. Unfractionated heparin (UFH), the mainstay of antithrombotic therapy, carries the risk of bleeding and associated interventions, and must be closely monitored. UFH therapy also has an increased risk of heparin-induced thrombocytopenia (HIT) and osteoporosis. These drawbacks prompted the development of newer antithrombotic agents, particularly low molecular weight heparins (LMWH) and factor Xa inhibitors. LMWH have several clinical advantages over UFH and has been demonstrated to be more effective than UFH in ACS. Because UFH is inexpensive, newer therapies need to demonstrate economic attractiveness over UFH. In addition to acquisition costs, it is important to consider the cost of all key components throughout the continuum of care. Health economic analyses show that the clinical advantages of the LMWH enoxaparin are also likely to result in net cost-saving benefits, due to reductions in diagnostic catheterization, percutaneous transluminal coronary angioplasty, and intensive care unit length of stay. Fondaparinux, an indirect inhibitor of factor Xa, does not require routine monitoring or multiple daily dosing, and is unlikely to interact with HIT antibodies. Large randomized clinical trials have shown that fondaparinux is at least as safe and efficacious as enoxaparin or UFH in the prevention of venous thromboembolism (VTE) and treatment of deep vein thrombosis or pulmonary embolism. Data from 2 recently published trials are similarly indicating noninferiority of fondaparinux in ACS patients. Health economic analysis of fondaparinux treatment is currently limited to VTE scenarios but point to a cost benefit associated with fondaparinux compared with enoxaparin.

Outcomes of Oral Anticoagulant Therapy Managed by Telephone vs In-Office Visits in an Anticoagulation Clinic Setting

BACKGROUND

Anticoagulation management by a dedicated anticoagulation clinic improves patient outcomes compared to routine medical care. Telephone-based anticoagulation management has been described but has not been compared to management with traditional office-based visits. The objective of this study was to compare warfarin-related monitoring outcomes, clinical end points, and the use of health-care resources as a result of warfarin-related complications in anticoagulation clinic patients whose management was conducted by telephone or in-office-based visits.

SETTING

Two university-affiliated anticoagulation clinics in Seattle, WA, and Chicago, IL.

METHODS

A retrospective, observational cohort design was used to investigate anticoagulation clinic patients who were managed by telephone encounters compared to those managed during face-to-face in-office encounters.

RESULTS

A total of 234 patients were evaluated; 117 patients managed by telephone were compared to 117 patients managed in office-based clinic visits. Monitoring outcomes (ie, time in therapeutic range and clinic visits per patient-year) were similar between groups. Differences in major bleeding (5.67% vs 5.62% per patient-year, respectively) and thromboembolic events (1.42% vs 2.81% per patient-year, respectively) between telephone-managed and face-to-face-managed patients did not reach statistical significance. The same was true for differences in the frequency of emergency department visits and hospital admissions to manage complications of warfarin therapy.

CONCLUSIONS

Telephone-based management of oral anticoagulation through a pharmacist-staffed anticoagulation clinic yielded clinical outcomes that were at least as favorable as those associated with traditional office-based visits. Telephone follow-up can be successfully used to manage warfarin therapy in patients who are unable to present in person to an anticoagulation clinic.

Economic considerations in managing patients with chronic stable angina

OBJECTIVE

To quantify the economic burden of chronic stable angina in the United States, characterize recent trends in the use of coronary revascularization, and compare the clinical outcomes and long-term costs of percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG), and medical management in patients with stable angina.

SUMMARY

The direct and indirect costs of stable angina are measured in tens of billions of dollars in the United States, with hospitalization contributing a large amount to the costs. The use of coronary revascularization, particularly PCI and insertion of coronary stents, has increased dramatically in recent years. The long-term costs of PCI and CABG are similar and high. Revascularization is sometimes used without an adequate trial of medical management, despite higher costs and a lack of evidence of long-term clinical benefits from revascularization.

CONCLUSION

Chronic stable angina is a costly condition. Medical management should be used before considering costly revascularization, unless medical management is contraindicated.

Sex Difference in the Antiplatelet Effect of Aspirin in Patients with Stroke

Background:

There is substantial interpatient variability in response to aspirin after an ischemic stroke or transient ischemic attack (TIA), as assessed by ex vivo effects of aspirin on platelet aggregation. The factors contributing to this variability are not well defined.

Objective:

To determine whether demographic, social, or clinical characteristics are associated with ex vivo response to aspirin in patients with a history of stroke or TIA.

Methods:

Eighty-one patients who were taking aspirin for secondary stroke prevention and underwent ex vivo platelet aggregation studies were identified. The medical records of eligible patients were reviewed by clinicians who specialize in the management of stroke patients. Characteristics were compared between 45 patients who had a complete response to aspirin and 36 patients who exhibited an incomplete (partial) response to aspirin based on the results of platelet aggregation testing.

Results:

The median (range) aspirin dose was similar in complete (325; 81–1950 mg/day) and partial (325; 81–1300 mg/day) responders. There was no association between aspirin response and age, race, body mass index, medical history, smoking status, or use of statin or hormone replacement therapy. However, sex was significantly associated with response to aspirin, with more women in the partial versus complete responder group (75% vs 49%; p = 0.02).

Conclusions:

Our data suggest that aspirin may be less effective at inhibiting platelet aggregation in women compared with men who have a history of ischemic stroke or TIA.

Different contributions of polymorphisms in VKORC1 and CYP2C9 to intra- and inter-population differences in maintenance dose of warfarin in Japanese, Caucasians and African-Americans

OBJECTIVE

To investigate pharmacokinetic and pharmacodynamic factors associated with population differences in warfarin doses needed to achieve anticoagulation, in particular the possible involvement of genetic variability in vitamin K epoxide reductase (VKOR) and CYP2C9.

METHODS

Warfarin maintenance dose, unbound plasma S-warfarin concentration [Cu(S)] and INR were determined in 157 Caucasians, 172 Japanese, and 36 African-Americans stably anticoagulated patients. In a subset (n = 166), fully carboxylated plasma normal prothrombin levels (NPT) were also measured. Genotyping for seven CYP2C9 (CYP2C9*1 through 6 and *11) and seven VKORC1 variants were performed in 115 Caucasians and 64 Japanese patients and 66 healthy African-Americans. Multivariate analysis was performed to identify covariates associated with warfarin requirement.

RESULTS

The relationship between NPT and Cu(S) indicated Japanese are more susceptible to inhibition of NPT production by S-warfarin than the other two populations. VKORC1 1173 C > T had a greater frequency in Japanese (89.1%) than Caucasians (42.2%) and African-Americans (8.6%). CYP2C9 variants with reduced metabolizing ability were less frequent in Japanese compared to the other two populations. The median warfarin dose was significantly higher in Caucasians than Japanese patients (5.5 versus 3.5 mg/day), however, when matched for CYP2C9*1 homozygosity, no difference in dose was observed between VKORC1 genotype-matched groups. Furthermore, VKORC1 1173C > T and CYP2C9 (*2/*3/*11) genotypes, age and weight were identified as independent covariates contributing to interpatient variability in warfarin dosage.

CONCLUSIONS

Both VKORC1 and CYP2C9 polymorphisms contribute to inter-population difference in warfarin doses among the three populations, but their contribution to intra-population variability may differ within each population.

New Anticoagulant Agents: Direct Thrombin Inhibitors

Decades of research have been devoted to developing effective, safe, and convenient anticoagulant agents. In recent years, much emphasis has been placed on the development of direct thrombin inhibitors (DTIs) that offer benefits over agents like heparin and warfarin including the inhibition of both circulating and clot-bound thrombin; a more predictable anticoagulant response, because they do not bind to plasma proteins and are not neutralized by platelet factor 4; lack of required cofactors, such as antithrombin or heparin cofactor II; inhibiting thrombin-induced platelet aggregation; and absence of induction of immune-mediated thrombocytopenia. Various injectable DTIs are currently available and used for many indications. In addition, research is now focusing on oral DTIs that seem promising and offer various advantages, such as oral administration, predictable pharmacokinetics and pharmacodynamics, a broad therapeutic window, no routine monitoring, no significant drug interactions, and fixed-dose administration.

Factors that influence prescribing within a therapeutic drug class

RATIONALE, AIMS AND OBJECTIVES

The decision to prescribe one drug instead of another within the same therapeutic class may be influenced by a variety of drug-related, direct, or indirect factors; but little is known about which considerations are most important in such choices. The low-molecular-weight heparins (LMWHs) represent a class of drugs that are commonly used and for which therapeutic equivalence has been debated in the literature. The purpose of this study was to identify and compare factors perceived by doctors and clinical pharmacists to be influential in prescribing decisions among LMWHs.

METHODS

Doctors and clinical pharmacists were interviewed to elicit information and to rank factors that influence the prescribing and use of LMWHs in community hospitals in the United States. For each factor, the mean and median of the rating were determined along with the frequency distribution across ratings. The non-parametric Mann-Whitney U-test was used to examine differences between doctors and clinical pharmacists.

RESULTS

Both groups considered efficacy, formulary status, and policies restricting drug use to be highly influential in the decision to use one LMWH instead of another. Compared to clinical pharmacists, doctors rated personal experience as more influential, whereas they rated drug cost and prescribing guidelines lower.

CONCLUSIONS

These findings suggest that doctors and clinical pharmacists differentiate between LMWHs based on differences between products and because of hospital administrative programs (such as drug formularies). This information may be of value in designing programs to alter medication use.

Anticoagulation Monitoring Part 2: Unfractionated Heparin and Low-Molecular-Weight Heparin

OBJECTIVE

To review the availability, mechanisms, limitations, and clinical application of point-of-care (POC) devices used in monitoring anticoagulation with unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs).

DATA SOURCES

Articles were identified through a MEDLINE search (1966–August 2004), device manufacturer Web sites, additional references listed in articles and Web sites, and abstracts from scientific meetings.

STUDY SELECTION AND DATA EXTRACTION

English-language literature from clinical trials was reviewed to evaluate the accuracy, reliability, and clinical application of POC monitoring devices.

DATA SYNTHESIS

The activated partial thromboplastin time (aPTT) and activated clotting time (ACT) are common tests for monitoring anticoagulation with UFH. Multiple devices are available for POC aPTT, ACT, and heparin concentration testing. The aPTT therapeutic range for UFH will vary depending upon the reagent and instrument employed. Although recommended by the American College of Chest Physicians Seventh Conference on Antithrombotic and Thrombolytic Therapy, establishing a heparin concentration–derived therapeutic range for UFH is rarely performed. Additional research evaluating anti-factor Xa monitoring of LMWHs using POC testing is necessary.

CONCLUSIONS

Multiple POC devices are available to monitor anticoagulation with UFH. For each test, there is some variability in results between devices and between reagents used in the same device. Despite these limitations, POC anticoagulation monitoring of UFH using aPTT and, more often, ACT is common in clinical practice, particularly when evaluating anticoagulation associated with interventional cardiology procedures and cardiopulmonary bypass surgery.

Concomitant drug, dietary, and lifestyle issues in patients with atrial fibrillation receiving anticoagulation therapy for stroke prophylaxis

Atrial fibrillation is a common cardiac arrhythmia and the leading risk factor for stroke. In those at moderate to high risk of stroke, oral anticoagulation therapy with warfarin (a vitamin K antagonist) significantly reduces not only the frequency of such events but also their severity and the associated risk of death. However, achieving optimal anticoagulation with this agent is clinically challenging in view of its complex pharmacokinetic and pharmacodynamic profile. In this regard, concomitant drug therapy (both prescription and over-the-counter medications, including herbal products, vitamins, and various nutritional supplements), along with alcohol intake, dietary factors, and changes in lifestyle, can significantly affect anticoagulation control and thereby expose patients to the risk of bleeding or thromboembolic complications (due to over- and underanticoagulation, respectively). Therefore, it is recommended that intensified monitoring of anticoagulation be performed at initiation and discontinuation of concomitant drug therapy, and in the case of significant dietary and lifestyle changes. Moreover, many patients receive inadequate education and are unaware of such risks and their implications, highlighting the need for better awareness and education on this important aspect of anticoagulation therapy.

Barriers to patient self-testing of prothrombin time: national survey of anticoagulation practitioners

Oral anticoagulation with warfarin requires routine monitoring of prothrombin time, expressed as the international normalized ratio (INR). Patient self-testing for INR is common in Europe but not in the United States. In order to determine the frequency of INR self-testing among patients whose anticoagulant therapy is managed in U.S. anticoagulation clinics, to describe the processes that support this self-testing, and to identify the barriers as experienced by anticoagulation clinic providers, a three-part survey was mailed to 538 anticoagulation specialists in the United States. The response rate was 43.7%. Policies and procedures of almost 60% of anticoagulation clinics prohibited INR self-testing for enrolled patients. In addition, less than 1% of patients being managed by U.S. anticoagulation clinics use self-testing to obtain INR results. Primary barriers were the cost of self-testing instruments (78.7% of respondents), cost of reagent cartridges (60.4%), and fear that self-testing might lead to unintended self-management (35.7%). Over 75% of respondents believed that some reimbursement for the cost of self-testing devices and supplies would increase the likelihood that anticoagulation clinics would recommend INR self-testing.

A pharmacologic overview of current and emerging anticoagulants

For over 50 years, anticoagulant options for the treatment and prevention of thrombosis have been limited mainly to traditional agents such as unfractionated heparin and oral vitamin K antagonists such as warfarin. These traditional agents are fraught with limitations that complicate their clinical use. A variety of novel anticoagulants with improved pharmacologic and clinical profiles have recently been introduced or are in development, offering benefits over traditional therapies. Specifically, progress has been made in the development of low-molecular-weight heparins, factor Xa inhibitors, and direct thrombin inhibitors. Because of their convenience and ease of use, some of these novel compounds are competing with the traditional anticoagulants and are needed additions to the antithrombotic arsenal.

Emerging options in the treatment of venous thromboembolism

PURPOSE

The long-term consequences of recurrent venous thromboembolism (VTE) and post-thrombotic syndrome, clinical profiles of traditional and novel antithrombotic agents used to treat VTE, current treatment recommendations for acute symptomatic VTE, clinical experience with newer antithrombotic agents for acute treatment and extended secondary prevention of VTE, and an emerging VTE treatment paradigm are discussed.

SUMMARY

Novel antithrombotic agents, with more specific activity on the coagulation cascade, more predictable pharmacodynamics and pharmacokinetics, simpler dosing regimens, and few or no laboratory monitoring requirements, have been developed to overcome limitations associated with some of the nonspecific traditional anticoagulants. Unfractionated heparin (UFH) and low molecular weight heparin (LMWH) are currently the recommended options for initial anticoagulation in patients with acute VTE. Warfarin is the most commonly used agent for chronic anticoagulation. Emerging evidence now also supports the role of factor-Xa inhibitors and oral direct thrombin inhibitors in the acute treatment and extended secondary prevention of VTE. In recent clinical trials, fondaparinux (a synthetic factor-Xa inhibitor) was comparable in efficacy and safety to unfractionated heparin for the treatment of acute symptomatic PE and to the LMWH enoxaparin for treating acute DVT. Ximelagatran, an oral direct thrombin inhibitor, was comparable in safety and efficacy to enoxaparin plus warfarin for treatment of acute VTE (DVT with or without PE). In addition, ximelagatran has been demonstrated to be superior to placebo for the extended secondary prevention of VTE, when continued for an additional 18 months beyond an initial six months of therapy. The benefits of extended anticoagulation for secondary VTE prevention have also been recently demonstrated with both low (INR 1.5-2.0) and regular intensity (INR 2.0-3.0) warfarin therapy.

CONCLUSION

A new paradigm for treating VTE is evolving based on the results of recent research to incorporate the use of emerging antithrombotic therapies in the acute treatment period and both traditional and novel agents in the chronic, extended-treatment period.