Thymoma

A 38-year-old man comes to his primary care physician for evaluation of intermittent muscle weakness that began around three months ago. He reports having episodes of “seeing-double” and having difficulty chewing that occur in the evening and resolve the next morning. Past medical history is notable for asthma, for which he intermittently uses an albuterol inhaler. His temperature is 37.6°C (99.7°F), pulse is 65/min and blood pressure is 122/71 mmHg. During the physical examination, the patient is asked to look upwards toward the ceiling for 60 seconds. This maneuver elicits bilateral diplopia. The remainder of the examination is noncontributory. Workup is sent to confirm the diagnosis, and the patient is started on the first-line medication for his condition. Which of the following is a likely side-effect from overdose of this medication?