A 35-year-old woman presents with sudden onset pleuritic chest pain and dyspnea. She takes oral contraceptives and recently had a long-haul flight. Vitals: heart rate 115 per minute, respiratory rate 26 per minute, oxygen saturation 90 percent on room air. CT pulmonary angiography confirms pulmonary embolism. Which anticoagulant is appropriate for initial and long-term therapy in this hemodynamically stable patient?