Cholinergic Antagonists · Pharmacology

Why are muscarinic antagonists contraindicated in patients with narrow-angle glaucoma?

  1. They cause miosis, which blocks outflow through the canal of Schlemm
  2. They cause mydriasis, which obstructs the eye's drainage angle
  3. They increase the production of aqueous humor by the ciliary body
  4. They cause thinning of the corneal surface
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Correct answer: They cause mydriasis, which obstructs the eye's drainage angle

Anticholinergics cause mydriasis (pupil dilation). In patients with narrow-angle glaucoma, the iris can bunch up and physically block the trabecular meshwork, causing a rapid and dangerous increase in intraocular pressure.

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