Comparative Effectiveness of Enoxaparin vs Dalteparin for Thromboprophylaxis After Traumatic Injury

Enoxaparin 30 mg twice daily and dalteparin 5,000 units once daily are two common low-molecular-weight heparin (LMWH) thromboprophylaxis regimens used in the trauma population. Pharmacodynamic studies suggest that enoxaparin provides more potent anticoagulation than does dalteparin. In 2009, our institution switched its formulary LMWH from enoxaparin to dalteparin followed by a switch back to enoxaparin in 2013. Using a difference in differences design, we contrasted the change in the VTE rate accompanying the LMWH switch with the change in a control group of trauma patients given unfractionated heparin (UFH) during the same period. The study included 5,880 patients: enoxaparin period (enoxaparin, n = 2,371; UFH, n = 1,539) vs the dalteparin period (dalteparin, n = 1,046; UFH, n = 924). The VTE rate was unchanged in the LMWH group: 3.3/1000 days in the enoxaparin period vs 3.8/1000 days in the dalteparin period: rate ratio (RR), 1.16; 95% CI 0.74-1.81. The rate was also unchanged in the UFH control subjects: 5.7/1,000 days in the enoxaparin period vs 5.2/1,000 days in the dalteparin period: RR, 0.92; 95% CI, 0.61-1.38. After confounding adjustment, the ratio of the change in VTE rate between the LMWH and UFH groups was similar: RR, 1.06; 95% CI 0.71-2.00. A secondary analysis excluding patients with delayed or interrupted prophylaxis (or both) altered this estimate nonsignificantly in favor of enoxaparin: RR, 2.39; 95% CI, 0.80-7.09. Our results suggest that dalteparin has an effectiveness similar to that of enoxaparin in real-world trauma patients. Future research should investigate how the timing and consistency of prophylaxis affects LMWH effectiveness.