Mydriasert

Uses

Therapeutic purpose:

• Inflammatory conditions of the uveal tract.
• May be used in temporary lowering of intraocular pressure in glaucoma.

Diagnostic purpose:

• Retinal photography.
• Refractive errors.
• Fundus examination/photography.
• Slit lamp examination.

Pre-operative use: In order to undergo surgical procedure that requires the visualization of structures behind the iris, such as cataract extraction, vitrectomy and retinal detachment surgery.

Mydriasert is also used to associated treatment for these conditions: Diagnostic procedures

How Mydriasert works

Muscarinic acetylcholine receptors are involved in numerous ocular functions. The M₃ subtype is predominantly expressed by smooth muscle cells of the sphincter pupillae, which is a circular muscle of the iris, and ciliary muscles. In response to light or binding of acetylcholine, M₃ receptor signalling leads to contraction of the sphincter pupillae and pupil constriction. Contraction of the ciliary muscle via M₃ receptor signalling also leads to accommodation, adjusting the lens for near vision. The eye is also innervated by parasympathetic nerves: ciliary ganglion neurons project to the ciliary body and the sphincter pupillae muscle of the iris to control ocular accommodation and pupil constriction.

Tropicamide is a non-selective muscarinic antagonist that binds to all subtypes of muscarinic receptors. By binding to muscarinic receptors, tropicamide relaxes the pupillary sphincter muscle and causes pupil dilation. By blocking the muscarinic receptors of the ciliary body, tropicamide also prevents accommodation. Like other muscarinic antagonists, tropicamide inhibits the parasympathetic drive, allowing the sympathetic nervous system responses to dominate. Tropicamide is thought to ameliorate sialorrhea by blocking M₄ receptors expressed on salivary glands and reducing hypersalivation.

Dosage

Mydriasert dosage

Uveitis: 1-2 drops bid-qid or as required.

Diagnostic purpose/Pre-operative purpose: Instill 1-2 drops in the eye(s) 15-20 minutes before examination. If examination is not conducted within 20–30 minutes, an additional drop may be placed in the eye(s) to prolong the effect.

Side Effects

Elevated IOP (occasionally), stinging, blurred vision, tachycardia, photophobia, headache, parasympathetic stimulation and allergic reactions. Systemic effects include arrhythmias, hypertension and coronary artery spasm.

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.

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.

Precaution

Caution should be taken when administered with, or upto 21days after administration of monoamine oxidase (MAO) inhibitors as exaggerated adrenergic effects may result.

The possibility of psychotic reactions and behavioral disturbances should be considered in patients who are hypersensitive to anticholinergic drugs.

Use with extreme caution in infants.

Interaction

Tropicamide may interfere with the antihypertensive action of carbachol, pilocarpine or ophthalmic cholinesterase inhibitors.

Volume of Distribution

No information can be found.

Elimination Route

Following ocular administration of 40 μL drops of 0.5% tropicamide in female subjects, tropicamide reached its mean peak concentration in plasma of 2.8 ± 1.7 ng/mL (mean ± SD) at five minutes.

Half Life

Tropicamide has a plasma half-life of 30 minutes.

Clearance

No information can be found.

Elimination Route

No information can be found.

Pregnancy & Breastfeeding use

The safety of this medication during pregnancy or lactation has not been established.

Contraindication

This medication is contraindicated in these following cases

• Patients with hypersensitivity to any of the components and narrow angles or narrow angle glaucoma.
• Low birth weight infants and some elderly adults with severe arteriosclerotic cardiovascular or cerebrovascular disease.
• During intraocular operative procedures when the corneal epithelial barrier has been disturbed.

Acute Overdose

Excessive use in children and in certain susceptible individuals may produce systemic toxic symptoms.

Storage Condition

Keep out of the reach of children. Store in a cool, dry place, away from heat and direct light. Do not use more than 4 weeks after opening.

Innovators Monograph

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