Bengt I. Eriksson

Definition of major bleeding in clinical investigations of antihemostatic medicinal products in surgical patients

Summary.  The definition of major bleeding varies between studies on surgical patients, particularly regarding the criteria for surgical wound‐related bleeding. This diversity contributes to the difficulties in comparing data between trials. The Scientific and Standardization Committee (SSC), through its subcommittee on Control of Anticoagulation, of the International Society on Thrombosis and Haemostasis has previously published a recommendation for a harmonized definition of major bleeding in non‐surgical studies. That definition has been adopted by the European Medicines Agency and is currently used in several non‐surgical trials. A preliminary proposal for a parallel definition for surgical studies was presented at the 54th Annual Meeting of the SSC in Vienna, July 2008. Based on those discussions and further consultations with European and North American surgeons with experience from clinical trials a definition has been developed that should be applicable to all agents that interfere with hemostasis. The definition and the text that follows have been reviewed and approved by relevant co‐chairs of the subcommittee and by the Executive Committee of the SSC. The intention is to seek approval of this definition from the regulatory authorities to enhance its incorporation into future clinical trial protocols.

Rivaroxaban versus Enoxaparin for Thromboprophylaxis after Hip Arthroplasty

BACKGROUND This phase 3 trial compared the efficacy and safety of rivaroxaban, an oral direct inhibitor of factor Xa, with those of enoxaparin for extended thromboprophylaxis in patients undergoing total hip arthroplasty. METHODS In this randomized, double-blind study, we assigned 4541 patients to receive either 10 mg of oral rivaroxaban once daily, beginning after surgery, or 40 mg of enoxaparin subcutaneously once daily, beginning the evening before surgery, plus a placebo tablet or injection. The primary efficacy outcome was the composite of deep-vein thrombosis (either symptomatic or detected by bilateral venography if the patient was asymptomatic), nonfatal pulmonary embolism, or death from any cause at 36 days (range, 30 to 42). The main secondary efficacy outcome was major venous thromboembolism (proximal deep-vein thrombosis, nonfatal pulmonary embolism, or death from venous thromboembolism). The primary safety outcome was major bleeding. RESULTS A total of 3153 patients were included in the superiority analysis (after 1388 exclusions), and 4433 were included in the safety analysis (after 108 exclusions). The primary efficacy outcome occurred in 18 of 1595 patients (1.1%) in the rivaroxaban group and in 58 of 1558 patients (3.7%) in the enoxaparin group (absolute risk reduction, 2.6%; 95% confidence interval [CI], 1.5 to 3.7; P<0.001). Major venous thromboembolism occurred in 4 of 1686 patients (0.2%) in the rivaroxaban group and in 33 of 1678 patients (2.0%) in the enoxaparin group (absolute risk reduction, 1.7%; 95% CI, 1.0 to 2.5; P<0.001). Major bleeding occurred in 6 of 2209 patients (0.3%) in the rivaroxaban group and in 2 of 2224 patients (0.1%) in the enoxaparin group (P=0.18). CONCLUSIONS A once-daily, 10-mg oral dose of rivaroxaban was significantly more effective for extended thromboprophylaxis than a once-daily, 40-mg subcutaneous dose of enoxaparin in patients undergoing elective total hip arthroplasty. The two drugs had similar safety profiles. (ClinicalTrials.gov number, NCT00329628.)

Dabigatran etexilate versus enoxaparin for prevention of venous thromboembolism after total hip replacement: a randomised, double-blind, non-inferiority trial

BACKGROUND After hip replacement surgery, prophylaxis following discharge from hospital is recommended to reduce the risk of venous thromboembolism. Our aim was to assess the oral, direct thrombin inhibitor dabigatran etexilate for such prophylaxis. METHODS In this double-blind study, we randomised 3494 patients undergoing total hip replacement to treatment for 28-35 days with dabigatran etexilate 220 mg (n=1157) or 150 mg (1174) once daily, starting with a half-dose 1-4 h after surgery, or subcutaneous enoxaparin 40 mg once daily (1162), starting the evening before surgery. The primary efficacy outcome was the composite of total venous thromboembolism (venographic or symptomatic) and death from all causes during treatment. On the basis of the absolute difference in rates of venous thromboembolism with enoxaparin versus placebo, the non-inferiority margin for the difference in rates of thromboembolism was defined as 7.7%. Efficacy analyses were done by modified intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00168818. FINDINGS Median treatment duration was 33 days. 880 patients in the dabigatran etexilate 220 mg group, 874 in the dabigatran etexilate 150 mg group, and 897 in the enoxaparin group were available for the primary efficacy outcome analysis; the main reasons for exclusion in all three groups were the lack of adequate venographic data. The primary efficacy outcome occurred in 60 (6.7%) of 897 individuals in the enoxaparin group versus 53 (6.0%) of 880 patients in the dabigatran etexilate 220 mg group (absolute difference -0.7%, 95% CI -2.9 to 1.6%) and 75 (8.6%) of 874 people in the 150 mg group (1.9%, -0.6 to 4.4%). Both doses were thus non-inferior to enoxaparin. There was no significant difference in major bleeding rates with either dose of dabigatran etexilate compared with enoxaparin (p=0.44 for 220 mg, p=0.60 for 150 mg). The frequency of increases in liver enzyme concentrations and of acute coronary events during the study did not differ significantly between the groups. INTERPRETATION Oral dabigatran etexilate was as effective as enoxaparin in reducing the risk of venous thromboembolism after total hip replacement surgery, with a similar safety profile.

Extended duration rivaroxaban versus short-term enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a double-blind, randomised controlled trial

BACKGROUND The risk of venous thromboembolism is high after total hip arthroplasty and could persist after hospital discharge. Our aim was to compare the use of rivaroxaban for extended thromboprophylaxis with short-term thromboprophylaxis with enoxaparin. METHODS 2509 patients scheduled to undergo elective total hip arthroplasty were randomly assigned, stratified according to centre, with a computer-generated randomisation code, to receive oral rivaroxaban 10 mg once daily for 31-39 days (with placebo injection for 10-14 days; n=1252), or enoxaparin 40 mg once daily subcutaneously for 10-14 days (with placebo tablet for 31-39 days; n=1257). The primary efficacy outcome was the composite of deep-vein thrombosis (symptomatic or asymptomatic detected by mandatory, bilateral venography), non-fatal pulmonary embolism, and all-cause mortality up to day 30-42. Analyses were done in the modified intention-to-treat population, which consisted of all patients who had received at least one dose of study medication, had undergone planned surgery, and had adequate assessment of thromboembolism. This study is registered at ClinicalTrials.gov, number NCT00332020. FINDINGS The modified intention-to-treat population for the analysis of the primary efficacy outcome consisted of 864 patients in the rivaroxaban group and 869 in the enoxaparin group. The primary outcome occurred in 17 (2.0%) patients in the rivaroxaban group, compared with 81 (9.3%) in the enoxaparin group (absolute risk reduction 7.3%, 95% CI 5.2-9.4; p<0.0001). The incidence of any on-treatment bleeding was much the same in both groups (81 [6.6%] events in 1228 patients in the rivaroxaban safety population vs 68 [5.5%] of 1229 patients in the enoxaparin safety population; p=0.25). INTERPRETATION Extended thromboprophylaxis with rivaroxaban was significantly more effective than short-term enoxaparin plus placebo for the prevention of venous thromboembolism, including symptomatic events, in patients undergoing total hip arthroplasty.

Oral dabigatran etexilate vs. subcutaneous enoxaparin for the prevention of venous thromboembolism after total knee replacement: the RE‐MODEL randomized trial

Background: Oral anticoagulants, such as dabigatran etexilate, an oral, direct thrombin inhibitor, that do not require monitoring or dose adjustment offer potential for prophylaxis against venous thromboembolism (VTE) after total knee replacement surgery. Methods: In this randomized, double‐blind study, 2076 patients undergoing total knee replacement received dabigatran etexilate, 150 mg or 220 mg once‐daily, starting with a half‐dose 1–4 h after surgery, or subcutaneous enoxaparin 40 mg once‐daily, starting the evening before surgery, for 6–10 days. Patients were followed up for 3 months. The primary efficacy outcome was a composite of total VTE (venographic or symptomatic) and mortality during treatment, and the primary safety outcome was the incidence of bleeding events. Results: The primary efficacy outcome occurred in 37.7% (193 of 512) of the enoxaparin group vs. 36.4% (183 of 503) of the dabigatran etexilate 220‐mg group (absolute difference, −1.3%; 95% CI, −7.3 to 4.6) and 40.5% (213 of 526) of the 150‐mg group (2.8%; 95% CI,−3.1 to 8.7). Both doses were non‐inferior to enoxaparin on the basis of the prespecified non‐inferiority criterion. The incidence of major bleeding did not differ significantly between the three groups (1.3% vs. 1.5% and 1.3% respectively). No significant differences in the incidences of liver enzyme elevation and acute coronary events were observed during treatment or follow‐up. Conclusions: Dabigatran etexilate (220 mg or 150 mg) was at least as effective as enoxaparin and had a similar safety profile for prevention of VTE after total knee replacement surgery.

Postoperative fondaparinux versus postoperative enoxaparin for prevention of venous thromboembolism after elective hip-replacement surgery: a randomised double-blind trial

BACKGROUND Elective hip-replacement surgery carries significant risk of venous thromboembolism, despite use of thromboprophylaxis. We aimed to see whether the pentasaccharide fondaparinux, the first drug of a new class of synthetic antithrombotic agents, could reduce this risk to a greater extent than other available treatments. METHODS In a double-blind study, we randomly assigned 2275 consecutive patients aged 18 years or older who were undergoing elective hip-replacement surgery to receive postoperative subcutaneous injections of either 2.5 mg fondaparinux once daily or 30 mg enoxaparin twice daily. The primary efficacy outcome was venous thromboembolism to day 11. The main safety outcomes were bleeding and death. Patients were followed up for 6 weeks. FINDINGS We assessed venous thromboembolism to day 11 in 1584 (70%) of 2275 patients. By day 11, venous thromboembolisms were recorded in 48 (6%) of 787 patients on fondaparinux and in 66 (8%) of 797 patients on enoxaparin. The relative reduction in risk was 26.3% (95% CI -10.8 to 52.8, p=0.099). The two groups did not differ in the number of patients who died or in the number who had clinically relevant bleeding. INTERPRETATION In patients undergoing elective hip-replacement surgery, 2.5 mg fondaparinux once daily was not significantly more effective than 30 mg enoxaparin twice daily in reducing risk of venous thromboembolism. However, the lower risk recorded with fondaparinux than enoxaparin was clinically important, with no increase in clinically relevant bleeding.

Comparative Pharmacodynamics and Pharmacokinetics of Oral Direct Thrombin and Factor Xa Inhibitors in Development

For the past five decades, there has been little progress in the development of oral anticoagulants, with the choices being limited to the vitamin K antagonists (VKAs). The situation is changing with the development of orally active small molecules that directly target thrombin or activated factor X (FXa). The two agents in the most advanced stages of development are dabigatran etexilate and rivaroxaban, which inhibit thrombin and FXa, respectively. Both are approved in the EU and Canada for venous thromboprophylaxis in patients undergoing elective hip- or knee-replacement surgery. Other agents in the early stages of development include several FXa inhibitors (apixaban, DU 176b, LY 517717, YM 150, betrixaban, eribaxaban [PD 0348292] and TAK 442) and one thrombin inhibitor (AZD 0837). With a predictable anticoagulant response and low potential for drug-drug interactions, these new agents can be given in fixed doses without coagulation monitoring. This renders them more convenient than VKAs. While the anticoagulant effect of the new thrombin and FXa inhibitors is similar, differences in the pharmacokinetic and pharmacodynamic parameters may influence their use in clinical practice. Here, we compare the pharmacokinetic and pharmacodynamic features of these new oral agents.

A Comparison of Recombinant Hirudin with a Low-Molecular-Weight Heparin to Prevent Thromboembolic Complications after Total Hip Replacement

BACKGROUND Patients who undergo total hip replacement have a high risk of thromboembolic complications. Recombinant hirudin (desirudin), a specific inhibitor of thrombin, represents a new development in antithrombotic therapy. We compared the efficacy and safety of desirudin with those of a low-molecular-weight heparin (enoxaparin) for the prevention of thromboembolic complications in patients undergoing primary total hip replacement. METHODS Both treatments, which were assigned in a randomized, double-blind manner, were started preoperatively: enoxaparin on the evening before surgery, and desirudin within 30 minutes before the start of surgery. The dose of desirudin was 15 mg subcutaneously twice daily, and the dose of enoxaparin was 40 mg subcutaneously once daily. The duration of treatment was 8 to 12 days. Deep-vein thrombosis was verified by bilateral venography performed at the end of the treatment period or earlier, if there were clinical signs of deep-vein thrombosis. RESULTS At 31 centers in 10 European countries, 2079 eligible patients were randomly assigned to receive desirudin or enoxaparin. A total of 1587 patients were included in the primary analysis of efficacy. In the desirudin group, as compared with the enoxaparin group, there was a significantly lower rate of proximal deep-vein thrombosis (4.5 vs. 7.5 percent, P=0.01; relative reduction in risk, 40.3 percent) and a lower overall rate of deep-vein thrombosis (18.4 vs. 25.5 percent, P=0.001; relative reduction in risk, 28.0 percent). The safety profiles were similar in the two treatment groups. CONCLUSIONS When administered 30 minutes before total hip replacement surgery, desirudin is more effective than enoxaparin in preventing deep-vein thrombosis.

Pharmacokinetic Profile of the Oral Direct Thrombin Inhibitor Dabigatran Etexilate in Healthy Volunteers and Patients Undergoing Total Hip Replacement

Dabigatran etexilate is an oral low‐molecular‐weight direct thrombin inhibitor. Following oral administration, dabigatran etexilate is rapidly converted to its active form, dabigatran. The authors investigated the absorption, distribution, and elimination of a single 150‐mg dose capsule formulation of dabigatran etexilate in healthy volunteers and patients undergoing total hip replacement. In an open‐label, 3‐way crossover study, dabigatran etexilate was administered to 18 male volunteers in the fasted state, after administration of food and with coadministration of the proton pump inhibitor, pantoprazole. In a subsequent multicenter, open‐label study, 59 patients received a single dose of dabigatran etexilate, administered 1 to 3 hours following total hip replacement. In healthy volunteers, food had no effect on the extent of absorption of dabigatran etexilate, although there was reduced interindividual variability for dabigatran maximum plasma concentration and AUC0‐∞. A decrease in the mean dabigatran AUC0‐∞ (904 to 705 ng•h/mL) occurred with coadministration of pantoprazole. In patients undergoing total hip replacement, immediate onset of absorption was seen with the maximum plasma concentration of dabigatran occurring after 6 hours. The AUC0–24 of dabigatran was 88% of the steady‐state AUC using a preliminary tablet formulation and 106% of that seen in the healthy volunteer study. Compared with healthy volunteers, the postoperative profile was flattened with delayed peak concentrations. In summary, administration of the dabigatran etexilate capsule with food has no effect on the extent of dabigatran absorption, with a moderate decrease when coadministered with pantoprazole. Adequate plasma concentrations of dabigatran were seen with early postoperative administration of the dabigatran etexilate capsule. These pharmacokinetic characteristics confirm the suitability of this oral solid dosage form for use in future clinical trials.

A Once-Daily, Oral, Direct Factor Xa Inhibitor, Rivaroxaban (BAY 59-7939), for Thromboprophylaxis After Total Hip Replacement

Background— Rivaroxaban (BAY 59-7939)—an oral, direct Factor Xa inhibitor—could be an alternative to heparins and warfarin for the prevention and treatment of thromboembolic disorders. Methods and Results— This randomized, double-blind, double-dummy, active-comparator–controlled, multinational, dose-ranging study assessed the efficacy and safety of once-daily rivaroxaban relative to enoxaparin for prevention of venous thromboembolism in patients undergoing elective total hip replacement. Patients (n=873) were randomized to once-daily oral rivaroxaban doses of 5, 10, 20, 30, or 40 mg (initiated 6 to 8 hours after surgery) or a once-daily subcutaneous enoxaparin dose of 40 mg (given the evening before and ≥6 hours after surgery). Study drugs were continued for an additional 5 to 9 days; mandatory bilateral venography was performed the following day. The primary end point (composite of any deep vein thrombosis, objectively confirmed pulmonary embolism, and all-cause mortality) was observed in 14.9%, 10.6%, 8.5%, 13.5%, 6.4%, and 25.2% of patients receiving 5, 10, 20, 30, and 40 mg rivaroxaban, and 40 mg enoxaparin, respectively (n=618, per-protocol population). No significant dose–response relationship was found for efficacy (P=0.0852). Major postoperative bleeding was observed in 2.3%, 0.7%, 4.3%, 4.9%, 5.1%, and 1.9% of patients receiving 5, 10, 20, 30, and 40 mg rivaroxaban, and 40 mg enoxaparin, respectively (n=845, safety population), representing a significant dose–response relationship (P=0.0391). Conclusions— Rivaroxaban showed efficacy and safety similar to enoxaparin for thromboprophylaxis after total hip replacement, with the convenience of once-daily oral dosing and without the need for coagulation monitoring. When both efficacy and safety are considered, these results suggest that 10 mg rivaroxaban once daily should be investigated in phase III studies.