Cholinergic drugs: bethanechol: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Cholinergic drugs: bethanechol

Sample item

A 62-year-old man cannot void on the second day after hernia repair. Bladder scan shows 700 mL, the prostate is not enlarged and there is no mechanical obstruction. Which drug can be used to stimulate detrusor contraction?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Bethanechol

Bethanechol is a choline ester that is resistant to acetylcholinesterase and selectively stimulates muscarinic receptors in the bladder and gut. It is used for postoperative non-obstructive urinary retention. It is contraindicated in mechanical obstruction, asthma, peptic ulcer and bradycardia.

Option by option

  • A. Bethanechol (correct)

    Correct. A muscarinic agonist contracts the detrusor and relaxes the trigone and sphincter.

  • B. Phenylephrine

    Phenylephrine stimulates alpha1 receptors and increases bladder neck tone, aggravating retention.

  • C. Oxybutynin

    Oxybutynin is an antimuscarinic and would relax the detrusor and worsen retention.

  • D. Hyoscine butylbromide

    Hyoscine butylbromide is an antimuscarinic antispasmodic and would reduce detrusor activity.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Pharmacology questions

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Bethanechol. Bethanechol is a choline ester that is resistant to acetylcholinesterase and selectively stimulates muscarinic receptors in the bladder and gut.

Why is "Phenylephrine" not the answer?

Phenylephrine stimulates alpha1 receptors and increases bladder neck tone, aggravating retention.

Why is "Oxybutynin" not the answer?

Oxybutynin is an antimuscarinic and would relax the detrusor and worsen retention.

Why is "Hyoscine butylbromide" not the answer?

Hyoscine butylbromide is an antimuscarinic antispasmodic and would reduce detrusor activity.

What concept does this question test?

It tests Cholinergic drugs: bethanechol in Pharmacology. It is used for postoperative non-obstructive urinary retention. It is contraindicated in mechanical obstruction, asthma, peptic ulcer and bradycardia.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Cholinergic drugs: bethanechol?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.