Parenteral agents include unfractionated heparin (UFH), low molecular weight heparin (LMWH) (eg, enoxaparin, dalteparin), Xa inhibitors (fondaparinux), and direct thrombin inhibitors (eg, bivalirudin, lepirudin, argatroban). UFH and LMWH are used to treat and prevent deep vein thrombosis, as well as pulmonary embolism (PE), unstable angina, and acute myocardial infarction. Enoxaparin 1 milligram/kilogram SC every 12 hours may be used in outpatient management of DVT. Dosing regimens for UFH and LMWH are weight based. UFH requires monitoring of the activated partial thromboplastin time (aPTT). Therapeutic range is 1.5 to 2.5 "normal" value. Heparin and LMWH may be used during pregnancy. Bivalirudin and argatroban are alternatives to UFH and LMWH during percutaneous intervention (PCI) for acute coronary syndrome (ACS). The 2 major complications of heparin are bleeding and heparin induced thrombocytopenia (HIT). Use hirudin, lepirudin, or argatroban for anticoagulation in patients with HIT. LMWH carries a lower bleeding risk than UFH, but a higher bleeding risk in patients with renal disease. LMWH may also cause pruritis, local skin reaction, or rarely, skin necrosis.