Initiation and Reinitiation of Anticoagulation Therapy

A thorough understanding of the pharmacology, pharmacokinetics, and pharmacodynamics of the most commonly prescribed anticoagulants is necessary to ensure optimal therapeutic outcomes and patient safety. Evidence is available to guide some, but not all aspects of anticoagulation therapy initiation. Issues related to the initiation of anticoagulation therapy, including the resumption of therapy following interruption of anticoagulation for invasive procedures, are reviewed. Initiating unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), or fondaparinux is challenging for patients with renal dysfunction and obesity. UFH is preferred in patients with severe renal dysfunction. Morbidly obese patients may require higher than usual prophylactic doses of LMWH. Therapeutic doses of LMWH should be based on actual body weight, even in obese patients. Currently available evidence does not demonstrate the superiority of one initial warfarin dose over another. All anticoagulants increase the risk of bleeding and should therefore only be initiated in appropriately selected patients with sufficiently low underlying bleeding risk.