Tropicamide

Tropicamide is a short-acting ophthalmic antimuscarinic that produces mydriasis with comparatively modest cycloplegia. Its main clinical role is pupillary dilation for ocular examination. A separate therapeutic application is selected postoperative pupillary management after cataract surgery, where a relatively brief effect permits changes in iris position between exposures.

Group

Ophthalmic antimuscarinic mydriatic

Mechanism of Action

Tropicamide antagonizes muscarinic receptors in the iris sphincter and ciliary muscle. Reduced parasympathetic contraction dilates the pupil and produces limited relaxation of accommodation-related muscle activity. The relatively short duration of receptor blockade permits recovery of pupillary movement. These effects facilitate examination and provide temporary pupillary control in selected postoperative eyes.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Diagnostic mydriasis	Reference only	TOPICAL		Apply ophthalmic solution to the eye once or twice before examination; the source does not establish a universal drop count.
Post-cataract pupil management	Reference only	TOPICAL	Every 8–12 h	Apply 2-3 times daily in the selected postoperative protocol; monitor pupil movement and IOP.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Diagnostic mydriasis	Reference only	TOPICAL		Apply ophthalmic solution to the eye once or twice before examination; the source does not establish a universal drop count.
Post-cataract pupil management	Reference only	TOPICAL	Every 8–12 h	Apply 2-3 times daily in the selected postoperative protocol; monitor pupil movement and IOP.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Diagnostic mydriasis	Reference only	TOPICAL		Apply ophthalmic solution to the eye once or twice before examination; the source does not establish a universal drop count.
Post-cataract pupil management	Reference only	TOPICAL	Every 8–12 h	Apply 2-3 times daily in the selected postoperative protocol; monitor pupil movement and IOP.

Indications

Selected postoperative pupillary management after cataract surgery to help reduce formation of iris adhesions within a specialist ophthalmic plan.

Contraindications

Use cautiously in patients predisposed to angle-closure glaucoma or elevated IOP.

Interactions

Other antimuscarinics may increase systemic or ocular effects.

Adverse effects

Stinging and hypersalivation, particularly in cats.
Can precipitate glaucoma in predisposed eyes and reduce Schirmer tear-test values temporarily.

Toxicity

Treat significant anticholinergic effects supportively and monitor IOP after excessive exposure.

Preparations

Preparation	Form	Strength	Route
Tropicamide ophthalmic solution 0.5%	Other	5 mg / mL	TOPICAL
Tropicamide ophthalmic solution 1%	Other	10 mg / mL	TOPICAL

Monitoring and Administration

Perform baseline tear tests before application when needed; the drug can alter tear-test results for several hours.

Peak dilation is often 15-30 minutes; effects commonly recede over 6-12 hours. It is less reliable than atropine for painful cycloplegia.