A 34-year-old man is brought to the emergency room with altered mental status after taking an unknown dose of a beta blocker to manage anxiety before a public lecture. His vital signs are as follows: temperature 99°F, heart rate 59 beats per minute, respiratory rate 14 breaths per minute, and blood pressure 80/55 mm Hg. On examination, he is disoriented but recognizes his wife, with cold extremities, bradycardia, and decreased breath sounds. ECG shows bradycardia with PR prolongation and first-degree heart block. Which of the following beta blockers is the most toxic in overdose?
