An 85-year-old woman is brought to the emergency department 90 minutes after the sudden onset of weakness of the left arm and face. She was well 3 hours ago and has had no prior strokes. History is significant for coronary artery disease and hypertension. She takes acetylsalicylic acid and lisinopril. Temperature is 36.4°C (97.5°F), pulse is 88/min and irregular, respirations are 16/min, and blood pressure is 170/96 mm Hg. Neurologic examination shows a left-sided facial droop and weakness of the left arm. Motor strength in the left leg is 5/5; sensory examination shows a left hemisensory deficit. CT scan of the head shows no acute intracranial process. The patient is from a culture that considers the use of blood products a sin. Which of the following is the MOST appropriate immediate medical therapy?