A 40-year-old female with a history of Graves' disease is brought to the emergency department with fever (103°F/39.4°C), tachycardia (140 bpm), agitation, and altered mental status. Her skin is warm and moist. Laboratory results reveal significantly elevated free T4 and T3. What is the most appropriate initial pharmacologic intervention?
✓ Correct Answer: Option B
Propylthiouracil (PTU) blocks new thyroid hormone synthesis and peripheral T4 to T3 conversion, making it the critical initial step in thyroid storm. It must precede iodine administration to prevent substrate delivery.