**4.3.2 Warfarin**

Warfarin has been used as VTE chemoprophylaxis in high-risk orthopedic patients for decades. It is an efficacious agent. However, it requires close monitoring. It can be both difficult and costly in the outpatient setting (Eikelboom & Weitz, 2007). It also has numerous drug-drug and drug-food interactions. These interactions can be particularly challenging considering the issue of poly-pharmacy in the elderly joint arthroplasty patient population. It also has a delayed onset of action, which may require bridging with a shorter acting anticoagulant such as LMWHs or unfractionated heparin. A recent paper by Caprini et al. noted that physicians often used inadequate bridging protocols in the postoperative period. This can have important clinical implications. They found that the 30-day mortality rate was found to be 6% for DVT and 12% for PE in this cohort (Caprini et al., 2005).
