- Concurrent or prior (within 7 days of enrollment) anticoagulation therapy, except: Use of low dose coumadin-type anticoagulants (≤ 2 mg PO QD) low molecular weight heparins (LMWH), e.g. Enoxaparin sodium (Lovenox) and unfractionated heparin for prophylaxis against central venous catheter thrombosis is allowed.