A patient with primary open-angle glaucoma is started on a miotic agent that acts by inhibiting acetylcholinesterase irreversibly. This drug also carries a risk of causing a paradoxical increase in intraocular pressure. Which of the following best describes this mechanism?

• A Stimulation of ciliary muscle contraction opening the trabecular meshwork
• B Reduction of aqueous humor production via beta-1 receptor blockade
• C Pupillary dilation causing angle closure in narrow-angle susceptible eyes
• D Breakdown of blood-aqueous barrier causing protein accumulation in the anterior chamber ✓

Explanation

Irreversible anticholinesterases such as echothiophate used in glaucoma can paradoxically raise IOP by breaking down the blood-aqueous barrier, leading to protein exudation and subsequent pupillary block or inflammatory trabecular obstruction. This is a recognised but uncommon complication distinct from the intended miotic, trabecular-opening effect. Options B and C describe the therapeutic mechanisms, not the paradoxical rise, and D applies to anticholinergic mydriatics, not miotics.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.