Autonomic Pharmacology USMLE Step 1 Practice Question

A 19-year-old woman is brought to the emergency department by her roommate because of acute confusion that developed approximately 2 hours after ingesting several tablets from a friend's motion sickness medication. Her temperature is 38.8°C, blood pressure is 145/90 mmHg, heart rate is 118/min, and respirations are 18/min. On examination, she is flushed, delirious, and unable to follow commands. She has dry mucous membranes, bilateral mydriasis with absent light reflexes, urinary retention requiring catheterization, and markedly decreased bowel sounds. Her skin is warm and dry. ECG shows a normal QRS duration and sinus tachycardia without prolonged QTc. Which of the following drugs would most directly reverse her mental status changes?