Cholinergic Drugs

A 68-year-old man with benign prostatic hyperplasia and urinary retention is prescribed a cholinergic agent to improve bladder emptying. Which drug is the first-line choice for this indication?

Which pharmacological feature best distinguishes direct-acting cholinergic agonists (acetylcholine, bethanechol) from indirect-acting agents (physostigmine, neostigmine)?

Edrophonium is used diagnostically in myasthenia gravis because it produces a rapid onset of action. Which of the following best explains this pharmacokinetic property?

A 52-year-old woman with myasthenia gravis (MG) is on pyridostigmine 60 mg four times daily. She presents to the clinic with progressive weakness, ptosis, and diplopia over the past 3 days despite compliance with her medication. On examination, she has a respiratory rate of 24/min, weak voice, and difficulty swallowing. A single-dose edrophonium (Tensilon) test is performed: within 30 seconds, her symptoms dramatically worsen. Which of the following best explains this clinical response and guides the next therapeutic step?

A 68-year-old man with a history of benign prostatic hyperplasia and urinary retention presents to the emergency department with acute angle-closure glaucoma. His intraocular pressure (IOP) is 58 mmHg, and he has corneal edema and a mid-dilated pupil. The ophthalmologist prescribes pilocarpine drops immediately. Within 2 hours, his IOP drops to 32 mmHg. However, the patient develops severe bronchospasm, profuse salivation, and bradycardia (HR 42/min). Which of the following best explains the adverse effect profile observed in this patient?