Initial anticoagulation Initial anticoagulation choices for acute PE include Intravenous unfractionated heparin Subcutaneous low molecular weight heparin Subcutaneous fondaparinux Factor Xa inhibitors (apixaban and rivaroxaban) Intravenous argatroban for patients with heparin - induced thrombocytopenia Intravenous unfractionated heparin has a short half-life (useful when the potential for bleeding is deemed higher than usual) and is reversible with protamine.