Muscarinic antagonists (mydriatics)
Muscarinic antagonists for mydriasis
Application of muscarinic antagonists in the eye (also called mydriatics) is mostly used for diagnostic purposes. According to their mechanism of action, mydriatics belong to the group of parasympathicolytics. By dilating the pupil via sphincter muscle relaxation, these drugs can improve the view into the eye and facilitate ophthalmological diagnostics. Muscarinic antagonists have a therapeutic application in iridocyclitis.
Which drug of the group of muscarinic antagonists is used, depends on the desired duration of action. Tropicamide has a short duration of action (5–8 hours), whereas cyclopentolate and homatropine are longer-lasting (12–24 hours). Atropine has the longest duration of action (1–2 weeks).
These parasympathicolytics also cause relaxation of the ciliary muscle (cycloplegia), which inhibits accommodation. The dilated pupil can cause acute glaucoma and intolerance to light.