Postdischarge oral versus injectable anticoagulation following major orthopedic surgery

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

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.

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.

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.

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.