Prophylactic agent	Study	Outcomes	NNT	Recommendation/comments	SORT evidence rating*
Aspirin	Evidence-based guidelinesA1,A2	Rates of DVT and fatal PE were significantly reduced with aspirin (ARR, 0.4 percent each).	250	Aspirin confers much less protection compared with other prophylactic agents; aspirin should not be used alone.A1	C
Fondaparinux (Arixtra) (2.5 mg SC once per day)	Double-blind randomized studyA3	By the 11th postoperative day, the incidence of VTE was significantly reduced with fondaparinux compared with enoxaparin (Lovenox) (RRR, 56.4; 95% CI, 0.39 to 70.3)	9	Fondaparinux is an FDA-approved agent available for prevention of VTE in patients with hip fracture.	B
LMWH or unfractionated heparin	Cochrane meta-analysisA4	Significant reduction in lower extremity DVT with LMWH (RR, 0.55; 95% CI, 0.34 to 0.88) or unfractionated heparin (RR, 0.59; 95% CI, 0.49 to 0.72) compared with control or no prophylaxis.	7	Slight increase in postoperative bleeding with both LMWH and unfractionated heparin	A
Warfarin (Coumadin) (INR, -2.0 to 2.7)	Pooled data from a review of RCTsA1	Significant reduction in the rates of DVT with warfarin (RRR, 61 percent) when compared with placebo	-	Problems with over- or under-anticoagulation; need for frequent INR monitoring	A