Tropicamide is a muscarinic (cholinergic) antagonist with pharmacological activity similar to atropine. Being relatively weak and short acting (effects lasting about 6 hours), it is clinically useful in producing dilation of the pupils (mydriasis) to facilitate fundal examination and measurement of refractive errors Pollack et al.

Drug Class

Cycloplegics/Mydriatics

Uses

Tropicamide is an alkaloid atropine‐derived anticholinergic drug and a non‐selective antagonist of muscarinic acetylcholine (mACh) receptors. Usually available in ophthalmic formulations, tropicamide is used to cause mydriasis and cycloplegia for eye exams or ocular procedures. It is also used in combination with hydroxyamphetamine for the same indication. Oral tropicamide has been investigated as a potential drug to relieve sialorrhea in patients with Parkinson's Disease.

Mechanism of action

Tropicamide is an anticholinergic drug and that works by non‐selectively blocking muscarinic receptors to cause mydriasis and cycloplegia. It relaxes the pupillary sphincter to dilate the pupil.

Toxicity

Oral LD50 is 865 mg/kg in rats and 565 mg/kg in mice. Intraperitoneal LD50 is 1210 mg/kg in rats and 695 mg/kg in mice. Subcutaneous LD50 is 872 mg/kg in rats and 665 mg/kg in mice.

Side effects

There is limited information on tropicamide overdose. Systemic adverse effects, such as tachycardia, central nervous system disturbances, and muscle rigidity have been reported with the use of tropicamide. Psychotic reactions, behavioral disturbances, and vasomotor or cardio-respiratory collapse have been reported with the use of anticholinergic in children.

Administration

Administration requires the removal of contact lenses. This topical ophthalmic solution is instilled into the eye in droplet form. The lacrimal sac should be compressed with the fingertip for 2 to 3 minutes after administration to reduce systemic absorption and systemic adverse effects. The tip of the dropper should not touch any surface as it might contaminate the drug. In a child, ensure the drug does not get to their mouth. Hands require washing before and after instilling the drop. The individual should avoid driving and not engage in potentially hazardous activities during pupillary dilation. After pupillary dilation, sensitivity to light may occur, and sunglasses may be necessary.