Endocrine Pharmacology USMLE Step 1 Practice Question

A 34-year-old woman with a known history of Graves' disease who ran out of her methimazole prescription three weeks ago is brought to the emergency department by her husband, who reports she has been increasingly confused and restless over the past 24 hours. Her temperature is 39.8°C, heart rate is 142 beats per minute, blood pressure is 158/72 mmHg, and respiratory rate is 22 breaths per minute. On examination, she is diaphoretic, tremulous, and visibly agitated, with a diffusely enlarged thyroid gland and prominent exophthalmos. She has had multiple episodes of vomiting and watery diarrhea since yesterday. Laboratory workup reveals a markedly suppressed TSH of less than 0.01 mIU/L and a free T4 of 6.8 ng/dL. In addition to initiating a thionamide, the treatment team administers a drug that rapidly decreases peripheral conversion of T4 to T3 while simultaneously controlling adrenergic symptoms. Which of the following drugs was most likely given?