Ocular pharmacology: timolol: 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 · Ocular pharmacology: timolol

Sample item

A 64-year-old man with primary open-angle glaucoma starts a new eye drop and within weeks develops wheeze and a pulse of 48 per minute. Which drug and mechanism of lowering intraocular pressure fit best?

ADorzolamide, which blocks the sodium-potassium pumpBBrimonidine, which increases trabecular outflow onlyCLatanoprost, which increases uveoscleral outflowDTimolol, which reduces aqueous humour production by the ciliary epithelium

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

The answer and the reasoning

D. Timolol, which reduces aqueous humour production by the ciliary epithelium

Timolol is a non-selective beta-blocker; blocking beta2 receptors on the ciliary epithelium lowers aqueous production. Enough drug is absorbed through the nasolacrimal duct to cause bronchospasm and bradycardia, so it is avoided in asthma, COPD and heart block. Betaxolol is a cardioselective alternative.

Option by option

A. Dorzolamide, which blocks the sodium-potassium pump
Dorzolamide inhibits carbonic anhydrase and not the sodium-potassium pump; it causes bitter taste and stinging.
B. Brimonidine, which increases trabecular outflow only
Brimonidine acts on alpha2 receptors, mainly reducing aqueous production, and causes drowsiness and allergy.
C. Latanoprost, which increases uveoscleral outflow
Latanoprost increases uveoscleral outflow and causes iris pigmentation and eyelash growth, not wheeze.
D. Timolol, which reduces aqueous humour production by the ciliary epithelium (correct)
Correct. A topical beta-blocker can produce systemic bronchospasm and bradycardia.

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.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is D, Timolol, which reduces aqueous humour production by the ciliary epithelium. Timolol is a non-selective beta-blocker; blocking beta2 receptors on the ciliary epithelium lowers aqueous production.

Why is "Dorzolamide, which blocks the sodium-potassium pump" not the answer?

Dorzolamide inhibits carbonic anhydrase and not the sodium-potassium pump; it causes bitter taste and stinging.

Why is "Brimonidine, which increases trabecular outflow only" not the answer?

Brimonidine acts on alpha2 receptors, mainly reducing aqueous production, and causes drowsiness and allergy.

Why is "Latanoprost, which increases uveoscleral outflow" not the answer?

Latanoprost increases uveoscleral outflow and causes iris pigmentation and eyelash growth, not wheeze.

What concept does this question test?

It tests Ocular pharmacology: timolol in Pharmacology. Enough drug is absorbed through the nasolacrimal duct to cause bronchospasm and bradycardia, so it is avoided in asthma, COPD and heart block. Betaxolol is a cardioselective alternative.

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 Ocular pharmacology: timolol?

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.