Endocrine Pharmacology USMLE Step 1 Practice Question

A 34-year-old woman with a known history of Graves disease who discontinued her methimazole three weeks ago is brought to the emergency department by her husband, who reports she has been increasingly confused and restless for the past 24 hours. On examination, her temperature is 39.8°C, heart rate is 142 beats/min, blood pressure is 158/72 mmHg, and respiratory rate is 22 breaths/min. She is diaphoretic and tremulous, with diffuse thyroid enlargement, a palpable thrill, and exophthalmos noted on physical exam. Laboratory studies reveal a TSH of less than 0.01 mIU/L and a markedly elevated free T4. She has been vomiting repeatedly and has had multiple episodes of diarrhea. In addition to initiating a thionamide, the treatment team administers a drug that rapidly decreases peripheral conversion of T4 to T3 while simultaneously controlling her adrenergic symptoms. Which of the following drugs was most likely given?