A cost-effectiveness analysis of fondaparinux sodium compared with enoxaparin sodium as prophylaxis against venous thromboembolism: use in patients undergoing major orthopaedic surgery

Comparison of postoperative complications after total hip arthroplasty among patients receiving aspirin, enoxaparin, warfarin, and factor Xa inhibitors

Optimal prophylaxis for prevention of venous thromboembolism (VTE) after total joint arthroplasty (TJA) remains debated. The purpose of this study was to compare postoperative complications in patients receiving different VTE chemoprophylactic regimens. Using a nationwide healthcare database, 72,670 THA patients without a history of VTE were identified. Study cohorts received VTE prophylaxis within 30 days postoperatively. Odds ratios and 95% confidence intervals were used to assess 30-day and 90-day postoperative complications (hematoma, hemorrhage, transfusion, pulmonary embolism (PE), VTE, prosthetic joint infection (PJI), and incision/drainage (I&D)). Of the 72,670 THA patients, 25,966 received single medication VTE prophylaxis; 551 (2.12%) aspirin, 6791 (26.15%) enoxaparin, 12,008 (46.25%) warfarin, 5403 (20.81%) rivaroxaban, 876 (3.37%) fondaparinux and 337 (1.30%) apixaban. 30-day complications included; aspirin: I&D; warfarin: I&D, hematoma, hemorrhage, transfusion, PJI, PE and DVT; apixaban: hematoma and hemorrhage. 90-day complications included; aspirin: I&D; warfarin: I&D, hematoma, hemorrhage, transfusion, PJI, PE and DVT. Warfarin was the only anticoagulant associated with a higher risk for DVT, and the highest risk for 30-day and 90-day complications. Aspirin had the highest risk for I&D. Despite three times increased 30-day risk for bleeding, apixaban was effective in preventing VTE during the high-risk 3-month-period. Enoxaparin had the lowest risk for PE and DVT while rivaroxaban had the lowest risk for PJI, hematoma, I&D, hemorrhage and transfusion.

Economic analyses of venous thromboembolism prevention strategies in hospitalized patients: a systematic review

Introduction

Despite evidence-based guidelines for venous thromboembolism prevention, substantial variability is found in practice. Many economic evaluations of new drugs for thromboembolism prevention do not occur prospectively with efficacy studies and are sponsored by the manufacturers, raising the possibility of bias. We performed a systematic review of economic analyses of venous thromboembolism prevention in hospitalized patients to inform clinicians and policy makers about cost-effectiveness and the potential influence of sponsorship.

Methods

We searched MEDLINE, EMBASE, Cochrane Databases, ACP Journal Club, and Database of Abstracts of Reviews of Effects, from 1946 to September 2011. We extracted data on study characteristics, quality, costs, and efficacy.

Results

From 5,180 identified studies, 39 met eligibility and quality criteria. Each addressed pharmacologic prevention: low-molecular-weight heparins versus placebo (five), unfractionated heparin (12), warfarin (eight), one or another agents (five); fondaparinux versus enoxaparin (11); and rivaroxaban and dabigatran versus enoxaparin (two). Low-molecular-weight heparins were most economically attractive among most medical and surgical patients, whereas fondaparinux was favored for orthopedic patients. Fondaparinux was associated with increased bleeding events. Newer agents rivaroxaban and dabigatran may offer additional value. Of all economic evaluations, 64% were supported by manufacturers of a "new" agent. The new agent had a favorable outcome in 38 (97.4%) of 39 evaluations [95% confidence interval [CI] (86.5 to 99.9)]. Among studies supported by a pharmaceutical company, the sponsored medication was economically attractive in 24 (96.0%) of 25 [95% CI, 80.0 to 99.9)]. We could not detect a consistent bias in outcome based on sponsorship; however, only a minority of studies were unsponsored.

Conclusion

Low-molecular-weight heparins and fondaparinux are the most economically attractive drugs for venous thromboembolism prevention in hospitalized patients. Approximately two thirds of evaluations were supported by the manufacturer of the new agent; such drugs were likely to be reported as economically favorable.

Cost and outcomes associated with rivaroxaban vs enoxaparin for the prevention of postsurgical venous thromboembolism from a US payer's perspective

OBJECTIVE

The objective of this analysis was the evaluation of the outcomes and costs associated with rivaroxaban and enoxaparin for the prevention of postsurgical venous thromboembolism (VTE) in patients undergoing total hip replacement (THR) and total knee replacement (TKR) from the US payer perspective.

METHODS

VTE event rates have been reported in three Phase III clinical trials that compared rivaroxaban and enoxaparin for VTE prevention after orthopedic surgery during the prophylaxis (≤35 days for THR patients and 10-14 days for TKR patients) and post-prophylaxis periods (≤90 days following surgery). These data were used in this decision-analytic model to estimate and compare health outcomes and costs associated with rivaroxaban and enoxaparin. The base-case analysis considered the number and costs of symptomatic VTE events during the prophylaxis period only. A 90-day horizon was considered in the sensitivity analysis.

RESULTS

Following THR, when extended durations of prophylaxis (35 days) were compared, rivaroxaban was associated with lower costs than enoxaparin, with total saving costs of $695/patient. When an extended duration of rivaroxaban prophylaxis (35 days) was compared with a short duration (10-14 days) of enoxaparin prophylaxis, rivaroxaban was estimated to prevent 9.9 additional symptomatic VTE events per 1000 patients, while saving $244/patient (rate/1000 patients). In the TKR population, short duration of rivaroxaban prophylaxis was estimated to prevent 13.1 additional symptomatic VTE events per 1000 patients. It was also less costly than short duration enoxaparin prophylaxis, with a saving of $411/patient (rate/1000 patients).

LIMITATIONS

Only statistically significant differences were captured in the base-case economic analysis, and, therefore, differences in pulmonary embolism (PE) and bleeding events were not captured.

CONCLUSIONS

In this model, rivaroxaban reduced total treatment payer costs vs enoxaparin for the prevention of VTE in THR or TKR patients.

Extended prophylaxis of venous thromboembolism with fondaparinux in patients undergoing major orthopaedic surgery in Italy: a cost-effectiveness analysis

Enoxaparin is the most frequently used low-molecular weight heparin in the world, given in order to prevent venous thromboembolism (VTE) in patients undergoing major orthopaedic surgery (MOS). Fondaparinux is an effective and safe alternative. The aim of our study was to compare the cost-effectiveness of enoxaparin and fondaparinux in the extended thromboprophylaxis of patients undergoing MOS in Italy. A decision-tree model was developed: probabilities of symptomatic events were derived from the published trials; use of resources in Italy was evaluated by means of a questionnaire administered to a panel of experts. Only the direct costs of VTE (acute treatment of events and of complications) were considered. Cost units were derived from the current cost of drugs, and from the Italian National Healthcare tariffs in 2007. Incremental cost-effectiveness ratios were analysed at three time points: 30 days, 1 year and 5 years. The higher cost of fondaparinux was counterbalanced by reduced rates of early DVT, early PE and prophylaxis-related major bleeding. If compared with enoxaparin, after 30 days of extended prophylaxis, fondaparinux is associated with a savings of <euro> 48.83 per patient; at the end of the first year, the savings increased to <euro> 72.13, and after 5 years, the savings are <euro> 74.36. One-way sensitivity analysis shows that the results are robust to the variation in unit costs for VTE-related care, or in event rates for both treatments. In conclusion, our model shows that, when administered for extended prophylaxis of VTE following MOS, fondaparinux is more effective and cost saving than enoxaparin.

Cost effectiveness of venous thromboembolism pharmacological prophylaxis in total hip and knee replacement: a systematic review

Total hip and knee replacements (THR and TKR) are high-risk settings for venous thromboembolism (VTE). This review summarizes the cost effectiveness of VTE prophylaxis regimens for THR and TKR. We searched MEDLINE (January 1997 to October 2009), EMBASE (January 1997 to June 2009) and the UK NHS Economic Evaluation Database (1997 to October 2009). We analysed recent cost-effectiveness studies examining five categories of comparisons: (i) anticoagulants (warfarin, low-molecular-weight heparin [LMWH] or fondaparinux) versus acetylsalicylic acid (aspirin); (ii) LMWH versus warfarin; (iii) fondaparinux versus LMWH; (iv) comparisons with new oral anticoagulants; and (v) extended-duration (> or =3 weeks) versus short-duration (<3 weeks) prophylaxis. We abstracted information on cost and effectiveness for each prophylaxis regimen in order to calculate an incremental cost-effectiveness ratio. Because of variations in effectiveness units reported and horizon length analysed, we calculated two cost-effectiveness ratios, one for the number of symptomatic VTE events avoided at 90 days and the other for QALYs at the 1-year mark or beyond. Our search identified 33 studies with 67 comparisons. After standardization, comparisons between LMWH and warfarin were inconclusive, whereas fondaparinux dominated LMWH in nearly every comparison. The latter results were derived from radiographic VTE rates. Extended-duration prophylaxis after THR was generally cost effective. Small numbers prohibit conclusions about aspirin, new oral anticoagulants or extended-duration prophylaxis after TKR. Fondaparinux after both THR and TKR and extended-duration LMWH after THR appear to be cost-effective prophylaxis regimens. Small numbers for other comparisons and absence of trials reporting symptomatic endpoints prohibit comprehensive conclusions.

Cost-effectiveness of venous thromboembolism prophylaxis in total hip and knee replacement surgery: the evolving application of health economic modelling over 20 years

OBJECTIVES

In the last two decades, there has been considerable evolution of methods for cost-effectiveness modelling. Some of the first models were developed in the area of venous thromboembolism (VTE) prophylaxis. Hence, this area can serve as an important example to illustrate evolving standards. Our objectives are to document evolving methodology by describing VTE models, assess their critical strengths and weaknesses, and inform future advances for models in this therapeutic area.

RESEARCH DESIGN AND METHODS

A systematic review of economic models of primary VTE prevention following hip and knee replacement surgery was undertaken. Electronic searches of PubMed, EMBASE, the Cochrane library, and grey literature were conducted (1985-2006). Reference lists of included articles and reviews were examined for relevant studies.

RESULTS

Twenty-nine cost-effectiveness models were identified. Nineteen other cost-effectiveness analyses were excluded because they were not model-based; 16 were simple cost calculations and three were analyses of resource use data collected alongside clinical trials. The majority of models (24) were constructed as decision trees, frequently utilising previously published model structures, with some adaptation for new comparators, and/or addition of relevant events omitted by earlier models (e.g., bleeding due to prophylactic treatment). Later models have included Markov processes to model potential long-term consequences of VTE (recurrent VTE and post-thrombotic syndrome) over longer time horizons. Systematic identification of clinical evidence and more sophisticated analysis methods (e.g., Bayesian mixed-treatment comparisons and probabilistic sensitivity analyses) have recently been introduced.

CONCLUSIONS

Model structures have evolved substantially in this highly studied therapeutic area, with improvements made to the model structure, the comprehensiveness of clinical evidence included, and the underlying calculation methodology.

Postdischarge oral versus injectable anticoagulation following major orthopedic surgery

BACKGROUND

Multiple clinical studies have shown postdischarge anticoagulation to be beneficial following major orthopedic surgery (MOS); however, outpatient prophylaxis is not widely practiced.

OBJECTIVE

To quantify, from a third-party payer perspective, real-world clinical and economic outcomes for patients receiving injectable or oral anticoagulation as prophylaxis for venous thromboembolism (VTE) following discharge after MOS.

METHODS

A retrospective database analysis was conducted using outpatient medical and pharmacy data from the PharMetrics Patient-Centric Database (January 1, 2002, to March 31, 2006). Patients greater than 18 years of age with 9 months of continuous eligibility who received an anticoagulant in the outpatient setting following MOS were eligible. Patients were stratified into 2 cohorts: injectable (dalteparin, enoxaparin, fondaparinux) and oral (warfarin), and were matched 1:1 on demographic and clinical characteristics.

RESULTS

A total of 12,724 patients were included (injectable, 6362; oral, 6362). At 90 days, patients receiving oral anticoagulation were 20% more likely to experience a VTE than were those receiving an injectable agent (7.4% vs 6.3%; p = 0.02, OR 1.18; 95% CI 1.03 to 1.36). No significant differences in bleeding were observed (<0.4%). The average adjusted total 6-month costs were significantly (p < 0.001) higher for the oral versus injectable cohort ($18,039 vs $16,429). Medical costs in the oral cohort offset the higher pharmacy costs in the injectable cohort.

CONCLUSIONS

This study demonstrates that the risk of VTE extends to the outpatient setting following MOS, even with postdischarge anticoagulation. Injectable agents used in the outpatient setting may result in fewer clinical VTEs without increasing the risk for major bleeding. These findings support the data from controlled clinical studies and expand the evidence to the real-world setting. Despite higher pharmacy acquisition costs for injectable anticoagulants, injectable agents may offer significant per patient savings to third party payers.

Burden of deep vein thrombosis in the outpatient setting following major orthopedic surgery

BACKGROUND

Venous thromboembolism (VTE) is a known complication of major orthopedic surgery (MOS) with important clinical and economic consequences. Recently published orthopedic guidelines have focused on prevention of pulmonary embolism as a primary outcome, but deep vein thrombosis (DVT) occurrence should not be readily dismissed.

OBJECTIVE

To describe the burden of DVT following hospital discharge for MOS by assessing the impact of DVT on costs and resource utilization from the third-party payer perspective.

METHODS

Retrospective analysis used outpatient medical and pharmacy data from the PharMetrics Patient-Centric Database (January 1, 2002-March 31, 2006). Patients 18 years of age or older with a record of MOS were eligible for inclusion. Included patients were stratified based on the presence of a DVT during the first month after hospital discharge. Characteristics of the samples were described. The impact of DVT on total 6-month costs and resource utilization (readmissions, outpatient, emergency department visits) was assessed through statistical models.

RESULTS

Of the 32,899 patients in the analysis, 1221 (3.71%) had a record of DVT during the first month following discharge for MOS. Compared with patients who did not develop DVT, patients who developed DVT postdischarge were slightly older (56.5 vs 55.8 y; p = 0.0127), had a higher occurrence of prior VTE (26.2% vs 3.4%; p < 0.0001), and had undergone recent surgical procedures other than MOS (73.0% vs 69.6%; p = 0.0116). After controlling for potential confounders, DVT was associated with a 22% and 74% increase in the average number of expected outpatient and emergency department visits, respectively, during the 6-month postdischarge period but did not significantly impact the number of readmissions. Furthermore, total 6-month costs were significantly higher for patients who developed DVT, with an incremental increase of over $2000.

CONCLUSIONS

The burden of DVT following hospital discharge for MOS is substantial. Specifically, DVT increases total costs and outpatient and emergency department visits.

The pharmacoeconomics of deep vein thrombosis treatment

Venous thromboembolism (VTE), encompassing both deep vein thrombosis (DVT) and pulmonary embolism, remains a common and costly condition that is associated with significant morbidity and mortality. Treatment options for initial management of DVT include unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), and fondaparinux, which is the first of a new class of pentasaccharide antithrombotic agents with anti-factor Xa activity. LMWHs are an important tool in DVT management, offering advantages over UFH such as ease of dosing, lack of need for coagulation monitoring, and reduced risk for heparin-induced thrombocytopenia (HIT). Fondaparinux is also characterized by a simple dosing regimen, no need for coagulation monitoring, and potentially a lower risk of HIT compared with LMWH. In a recent clinical trial of DVT management, efficacy and bleeding rates with fondaparinux appeared similar to those observed with LMWH. In contrast to LMWH, fondaparinux is generally given as a fixed dose across a range of patient weights rather than calculated per individual patient weight. Given the increasing economic burden of VTE, particularly due to its increased rate among the elderly, pharmacoeconomic analyses have become a particularly useful tool to aid in selecting among similarly effective and safe agents for VTE treatment. A recent cost-effective analysis demonstrated that fondaparinux use offers an attractive economic alternative to other agents for initial DVT therapy that could yield cost savings without compromising clinical outcomes or patient safety.

Minimizing costs for treating deep vein thrombosis: the role for fondaparinux

BACKGROUND

Deep vein thrombosis (DVT) remains a major burden and fondaparinux represents a new option for DVT therapy. We sought to determine if fondaparinux offered financial advantages over low-molecular weight heparin since it is given as a fixed dose over a wide range of patient weights rather then dosed directly on weight and because fondaparinux is not associated with heparin-induced thrombocytopenia (HIT).

METHODS

We conducted a cost-minimization analysis comparing fondaparinux to enoxaparin for acute anticoagulation in DVT. We modeled a cohort of 1,000 hypothetical subjects and drew estimates for model inputs from the published literature. We completed multiple sensitivity analyses to asses the significance of our assumptions and used Monte Carlo simulation to estimate the 95% confidence intervals (CIs) around our estimation of the cost differential for the two agents.

RESULTS

In the base case, total disease management costs per patient with fondaparinux are US 472 dollars compared to 769 dollars with enoxaparin. The 95% CI around this difference ranges from US 48 dollars to US 401 dollars. The model was mildly sensitive to the pharmacy acquisition costs of fondaparinux and enoxaparin which was the major driver of overall costs. Neither the rates of nor costs associated with DVT recurrence, major bleeding, nor HIT substantially affected our observations. Breakeven analysis indicated our findings to be robust over a wide range of likely clinical scenarios.

CONCLUSIONS

From the perspective of a healthcare system, fondaparinux use offers an attractive economic alternative to other agents for initial DVT therapy. Expanded reliance on fondaparinux could potentially result in savings.

Pharmacoeconomic considerations in anticoagulant drug use

Anticoagulants are used for the prevention and treatment of venous thromboembolism and for the secondary prevention of stroke and myocardial infarction. The list of available anticoagulants includes unfractionated heparin, low molecular weight heparins, fondaparinux, warfarin and the direct thrombin inhibitors. Numerous randomised controlled trials have pitted one anticoagulant against another to ascertain superiority in terms of safety and efficacy. Differences in these outcomes are assessed using appropriate statistical tests. When a statistically significant difference is found, it is generally accepted that one option is superior to another. There is also an interest in whether there is a clinically significant difference between two or more treatments, even when there may not be a statistically significant difference. This decision is reached through clinical judgment based on logical and ethical considerations. Another important way to judge the difference between alternative treatment strategies is to test for economically significant differences. This is accomplished through pharmacoeconomic analysis. This paper reviews the evidence gathered from published studies designed to detect an economically significant difference between two or more anticoagulants used for the same clinical indication.

Cost-effectiveness of fondaparinux compared with enoxaparin as prophylaxis against venous thromboembolism in patients undergoing hip fracture surgery

OBJECTIVE

To evaluate the cost-effectiveness of fondaparinux relative to enoxaparin as prophylaxis against venous thromboembolism (VTE) in patients undergoing hip fracture surgery.

METHODS

A decision analysis model was created to simulate the impact of fondaparinux 2.5 mg once daily relative to enoxaparin 30 mg twice daily on patient outcomes and costs over various time points up to 5 years after surgery. Probabilities for the analysis were estimated for a hypothetical cohort of 1000 patients undergoing hip fracture surgery in the United States receiving either fondaparinux or enoxaparin according to comparative trial results. Resource use and costs (2003 dollars) were obtained from large health-care databases. Outcome measures were rates of symptomatic VTE events, health-care costs, and incremental cost-effectiveness ratios.

RESULTS

Fondaparinux is estimated to prevent an additional 30 VTE events (per 1000 patients) at 3 months compared with enoxaparin, producing savings of 103 dollars at discharge, 290 dollars over 1 month, 361 dollars over 3 months, and 466 dollars over 5 years. The results remain robust to clinically plausible variation in input parameters and assumptions.

CONCLUSIONS

Fondaparinux improves outcomes and is cost-saving over a broad range of assumptions compared with enoxaparin for prophylaxis of VTE after hip fracture surgery.

Short- and long-acting synthetic pentasaccharides as antithrombotic agents

Fondaparinux sodium (Arixtra; GlaxoSmithKline) is the first of a new class of antithrombotic agents. It is a chemically synthesised pentasaccharide mimicking the site of heparin that binds to antithrombin. It is purely a factor Xa inhibitor and an inhibitor of thrombin generation that requires binding to antithrombin. Fondaparinux sodium differs from heparin, low-molecular-weight heparin and heparinoids, and cannot be used interchangeably. It has been approved in the US and Europe for the prophylaxis of venous thrombosis after orthopaedic surgery by a fixed dose of 2.5 mg/day without monitoring. Using this pentasaccharide as a backbone, other structures have been synthesised. Idraparinux sodium (Sanofi-Aventis) differs structurally from fondaparinux sodium as it has additional methyl groups, a long half-life, and once-weekly administration. Both drugs are being developed as antithrombotics for venous and arterial thrombosis, acute coronary syndrome, stroke and as adjuncts to thrombolytic therapy.

Current concepts for the prevention of venous thromboembolism

Venous thromboembolism (VTE) is a major cause of morbidity and mortality worldwide and the annual incidence of VTE is 1 per 1000. The individual risk for venous thromboembolism may be substantially higher and is determined by expositional and dispositional factors. Unfractionated heparin and warfarin have been the mainstays for the prevention of VTE until the early 1980s. Bleeding complications and side effects limited the use of these agents and subsequently low molecular weight heparins (LMWH) were introduced into clinical practice. These are most commonly used for the prophylaxis and treatment of VTE today. In the last decade, the pace of development of further anticoagulants has accelerated with the introduction of new treatment regimens and new substances. In this context, novel drugs directed against clotting factor Xa (such as fondaparinux) and direct thrombin inhibitors (such as melagatran/ximelagatran) have been developed. Fondaparinux shows a favourable efficacy/safety profile and has been documented to be cost-effective compared to enoxaparin in the US and the UK.