Which Cholinergic Antagonist has the shortest duration of cycloplegic effects?

Cyclopentolate is the cholinergic antagonist with the shortest duration of cycloplegic effects, typically lasting about 24 hours. This is particularly valuable in ophthalmic practice for its ability to facilitate short-term examinations while minimizing prolonged effects, which can be problematic in patients who may need to function normally shortly after.

The mechanism of cyclopentolate involves the inhibition of the parasympathetic pathways responsible for accommodation and miosis, leading to temporary paralysis of the ciliary muscle (cycloplegia) and dilation of the pupil (mydriasis).

Compared to other agents like atropine, which can have effects lasting up to several days, or homatropine with effects lasting approximately 1-3 days, cyclopentolate provides a more immediate and short-lived solution for clinical evaluations. Tropicamide also has a relatively short duration of action, typically around 4-6 hours, but cyclopentolate is still shorter than this. Therefore, cyclopentolate is the preferred option when brief cycloplegia is needed.