Warfarin Failure: What are the treatment options if a patient develops a DVT while on warfarin?

If INR is subtherapeutic, less than 2.0, this is not a true warfarin failure.  Reinstitute heparin or LMWH until INR in target range.

If INR is therapeutic,  consider the following options 

• aim for a higher target INR, 3.0 - 4.0 
• switch to LMWH
• switch to Fondaparinux
• place an IVC filter, although this could serve as a nidus for subsequent thrombosis in the long run

Source

Cleveland Clinic Foundation Intensive Review of Internal Medicine.  2009.