Review Question - QID 214815

A 35-year-old woman presents to the emergency department with a 3-day history of epistaxis and rash on her lower extremities. She was recently hospitalized for a pulmonary embolism 1 month prior, which required treatment with heparin. She was subsequently discharged from the hospital on enoxaparin. She has a history of rheumatoid arthritis and takes no medications for this condition. She drinks 5 beers weekly and uses heroin intermittently. Her temperature is 98.6°F (37.0°C), blood pressure is 80/55 mmHg, pulse is 115/min, and respirations are 18/min. Physical exam reveals gingival and mucosal bleeding with multiple, erythematous, brown macules noted on her lower extremities that do not blanch with pressure as shown in Figure A. There is no hepatomegaly or splenomegaly. Laboratory results are listed below:

Leukocyte count: 10,000/mm^3
Hemoglobin: 12.2 g/dL
Platelet count: 18,000/mm^3
Prothrombin time (PT): 12 seconds
Partial thromboplastin time (PTT): 32 seconds
Aspartate aminotransferase (AST): 24 U/L
Alanine aminotransferase (ALT): 21 U/L

Which of the following is the most appropriate treatment?