Q. A 25-year-old female presents to the emergency department with a complaint of rapid heartbeat and palpitations for the past several days. She also reports over the past several months experiencing difficulty sleeping, feeling anxious, shortness of breath, tremors, and having occasional chest pain. The patient has no significant past medical history, and takes no medications regularly. On physical examination, she appears anxious and is sweating profusely. Her pulse rate is 132/min, blood pressure 160/90 mm Hg, respiratory rate 20/min, and her oxygen saturation is 99 percent on room air. You note a diffusely enlarged and tender thyroid gland. Her cardiopulmonary assessment is unremarkable. Her abdomen is soft, non-tender, and without organomegaly. No peripheral edema, rashes, or lesions, are noted. You order an electrocardiogram (see image), and bloodwork. Her thyroid-stimulating hormone level is 0.01 mIU/L, free thyroxine is 8.0 ng/dL, and her total triiodothyronine is 600 ng/dL. Based on the information you have at this point, which of the following medications is the best choice to administer to this patient?