Beta Blockers USMLE Step 1 Practice Question

A 41-year-old male farm worker is brought to the emergency department by coworkers after collapsing in a field where he had been spraying organophosphate insecticide for approximately three hours without protective equipment. On arrival, he is obtunded and diaphoretic, with copious secretions draining from his mouth and nose. Vital signs reveal a blood pressure of 88/54 mmHg, heart rate of 42 beats per minute, respiratory rate of 26 breaths per minute, and oxygen saturation of 87% on room air. Physical examination demonstrates bilateral miosis, diffuse expiratory wheezing, excessive lacrimation, urinary incontinence, and visible muscle fasciculations throughout his extremities. Point-of-care testing reveals markedly reduced plasma cholinesterase activity. Initial therapy includes a medication that rapidly improves his bronchorrhea and bradycardia by blocking muscarinic receptors. Which of the following drugs provides that effect?