Tropicamide

A medication used to dilate the pupil and aid in eye examinations

Chemical structure of Tropicamide

Tropicamide is a medication primarily used in ophthalmology to induce mydriasis (dilation of the pupil) and cycloplegia (paralysis of the ciliary muscle of the eye). It is commonly used to facilitate eye examinations, particularly for the assessment of the retina and optic nerve.

Pharmacology

Tropicamide is an antimuscarinic agent that works by blocking the muscarinic receptors in the eye, leading to relaxation of the sphincter muscle of the iris and the ciliary muscle. This results in pupil dilation and loss of accommodation. The effects of tropicamide are relatively short-lived compared to other mydriatic agents, making it suitable for diagnostic purposes.

Chemical Structure

(R)-Tropicamide structural formula

(S)-Tropicamide structural formula

Tropicamide is a synthetic compound with the chemical formula C17H20N2O2. It exists as a racemic mixture of two enantiomers, (R)-tropicamide and (S)-tropicamide, each with distinct structural formulas.

Clinical Use

Tropicamide is administered in the form of eye drops. It is typically used in concentrations of 0.5% or 1% for diagnostic purposes. The onset of action is rapid, with pupil dilation occurring within 15 to 30 minutes after administration. The effects generally last for 4 to 8 hours, although this can vary among individuals.

Indications

Tropicamide is indicated for:

• Facilitating fundoscopy and other ophthalmic examinations.
• Preoperative and postoperative management in certain eye surgeries.

Side Effects

Common side effects of tropicamide include:

• Transient stinging or burning sensation in the eyes.
• Increased sensitivity to light (photophobia).
• Blurred vision due to cycloplegia.

In rare cases, systemic absorption can lead to anticholinergic side effects such as dry mouth, flushing, and tachycardia.

Precautions

Tropicamide should be used with caution in patients with narrow-angle glaucoma or a predisposition to angle-closure glaucoma, as it can precipitate an acute attack. It is also advised to use caution in pediatric and elderly populations due to increased sensitivity to anticholinergic effects.

Mechanism of Action

Tropicamide acts as a competitive antagonist of the muscarinic acetylcholine receptors, particularly the M4 receptor subtype in the eye. By inhibiting the action of acetylcholine, tropicamide prevents the constriction of the pupil and the accommodation of the lens, leading to mydriasis and cycloplegia.

Related Pages

• Mydriatic
• Cycloplegia
• Antimuscarinic
• Ophthalmology

Anisocoria caused by Tropicamide

See Also

• Atropine
• Homatropine
• Phenylephrine