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Apixaban Versus Enoxaparin for Thromboprophylaxis in Medically Ill Patients
Study Questions:
Is extended-duration thromboembolism prophylaxis with apixaban more effective than short-term prophylaxis with enoxaparin in hospitalized medically ill patients?
Methods:
The ADOPT (Apixaban Dosing to Optimize Protection From Thrombosis) trial investigators reported the results of a double-blind, double-dummy, placebo-controlled trial of orally administered apixaban at a dose of 2.5 mg twice daily for 30 days, versus subcutaneously administered enoxaparin at a dose of 40 mg once daily for 6 to 14 days, in acutely ill hospitalized medical patients. Subjects had to be 40 years of age or older, and hospitalized for congestive heart failure, acute respiratory failure, infection without shock, inflammatory bowel disease, or acute rheumatic disorder, with an expected hospital stay of at least 3 days. Systematic, bilateral, compression ultrasonography was performed on day 30. The primary efficacy outcome was 30-day composite of death related to venous thromboembolism, pulmonary embolism, symptomatic deep-vein thrombosis (DVT), or asymptomatic DVT. All outcomes were independently adjudicated.
Results:
Out of 6,528 randomized subjects, 4,495 could be evaluated for the primary outcome. The primary outcome at 30 days was seen in 2.71% of subjects in the apixaban group versus 3.06% in the enoxaparin group (relative risk [RR], 0.87; 95% confidence interval [CI], 0.62-1.23; p = 0.44). Major bleeding was seen in 0.47% versus 0.19%, in the apixaban versus enoxaparin groups, respectively (RR, 2.58; 95% CI, 1.02-7.24; p = 0.04).
Conclusions:
The authors concluded that in medically ill patients, an extended course of thromboprophylaxis with apixaban was not superior to a shorter course of enoxaparin. Apixaban was associated with significantly more major bleeding events than was enoxaparin.
Perspective:
Apixaban can now join rivaroxaban and enoxaparin (low molecular weight heparin) as agents demonstrated to effectively prevent DVT in high-risk situations such as in medically ill, hospitalized, at-risk patients, but also demonstrated an increased risk of major bleeding when prophylaxis treatment is extended. While there was a trend toward lower rates of venous thromboembolism with apixaban versus enoxaparin, almost all of the difference occurred after the cessation of the shorter-term prophylaxis treatment with enoxaparin. Analogous to treatment regimens for idiopathic DVT, prophylactic treatment for venous thromboembolism in at-risk populations seems to be more effective with a longer duration of therapy. However, three different agents have now demonstrated a significantly higher rate of major bleeding with extended-duration thromboembolism prophylaxis in hospitalized medically ill patients. Unless a targeted population at higher risk can be identified for prophylaxis treatment, extended-duration thromboembolism prophylaxis for hospitalized medically ill patients cannot be recommended.
Keywords: Risk, Morpholines, Inflammatory Bowel Diseases, Pulmonary Embolism, Heparin, Low-Molecular-Weight, Venous Thromboembolism, Respiratory Insufficiency, Pyrazoles, Enoxaparin, Heart Failure, Cardiovascular Diseases, Venous Thrombosis, Confidence Intervals, Pyridones, Hemorrhage
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